{"kind": "storage", "major": "18", "item": {"slug": "tuple-layout", "name": "Table row layout", "name_zh": "", "category": "\u7269\u7406\u7ed3\u6784", "summary": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 66.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask 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\u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u603b\u5171\u4e3a t_natts \u4f4d\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 69.2 \u8282 \uff09\u3002", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a069.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u603b\u5171\u4e3a t_natts \u4f4d\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a069.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "summary": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 69.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u603b\u5171\u4e3a t_natts \u4f4d\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 69.2 \u8282 \uff09\u3002", "version": "11", "link_map": {"/zh/docs/11/storage-toast.html": "/docs/11/storage-toast.html", "/zh/docs/11/storage-page-layout.html#STORAGE-TUPLE-LAYOUT": "/docs/11/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "/zh/docs/11/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE": "/docs/11/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE"}, "body_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a069.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u603b\u5171\u4e3a t_natts \u4f4d\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a069.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

", "body_sha256": "50a7d55eeae69dc041fc5c37bcb8a4c18df130a02b177a599681f50aeebdbdcc", "content_hash": "d46670d015e0d0bc1ed2e38ca9013dbc8421e08e98961e3fc1a99f107fae4694", "source_database": "center", "source_revision": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}, "signature": "", "tables_zh": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "description": ["\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 69.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u603b\u5171\u4e3a t_natts \u4f4d\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 69.2 \u8282 \uff09\u3002"], "manual_html": "", "manual_path": "/docs/11/storage-page-layout.html", "sections_zh": [], "localization": {"status": "complete", "sources": [{"url": "/docs/11/storage-page-layout.html", "method": "same-major semantic node", "sha256": "2e786c1b60ec8abf4a16033196a1e0170710e61ad0177788b174748ccda0ac62", "language": "zh", "matched_nodes": ["#STORAGE-PAGE-LAYOUT/div[15]/div[2]/p[0]", "#STORAGE-PAGE-LAYOUT/div[15]/p[1]", "#STORAGE-PAGE-LAYOUT/div[15]/p[4]", "#STORAGE-PAGE-LAYOUT/div[15]/p[5]", "#STORAGE-PAGE-LAYOUT/div[15]/p[6]", "#STORAGE-PAGE-LAYOUT/div[1]"]}], "language": "zh", "original_text": {"/versions/11/description/0": "Physical row headers, null bitmap, alignment and column data.", "/versions/11/tables/0/title": "HeapTupleHeaderData Layout", "/versions/11/tables/0/rows/0/c2": "4 bytes", "/versions/11/tables/0/rows/0/c3": "insert XID stamp", "/versions/11/tables/0/rows/1/c2": "4 bytes", "/versions/11/tables/0/rows/1/c3": "delete XID stamp", "/versions/11/tables/0/rows/2/c2": "4 bytes", "/versions/11/tables/0/rows/2/c3": "insert and/or delete CID stamp (overlays with t_xvac)", "/versions/11/tables/0/rows/3/c2": "4 bytes", "/versions/11/tables/0/rows/3/c3": "XID for VACUUM operation moving a row version", "/versions/11/tables/0/rows/4/c2": "6 bytes", "/versions/11/tables/0/rows/4/c3": "current TID of this or newer row version", "/versions/11/tables/0/rows/5/c2": "2 bytes", "/versions/11/tables/0/rows/5/c3": "number of attributes, plus various flag bits", "/versions/11/tables/0/rows/6/c2": "2 bytes", "/versions/11/tables/0/rows/6/c3": "various flag bits", "/versions/11/tables/0/rows/7/c2": "1 byte", "/versions/11/tables/0/rows/7/c3": "offset to user data", "/versions/11/tables/0/columns/0/label": "Field", "/versions/11/tables/0/columns/1/label": "Type", "/versions/11/tables/0/columns/2/label": "Length", "/versions/11/tables/0/columns/3/label": "Description"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "d562e8dfe3b04c94ffb663deceba6acde64cb2369268b1869886b570fefe4c8b", "canonical_center_text_hash": "d46670d015e0d0bc1ed2e38ca9013dbc8421e08e98961e3fc1a99f107fae4694"}, "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 69.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u603b\u5171\u4e3a t_natts \u4f4d\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 69.2 \u8282 \uff09\u3002", "comparison_data": {"layouts": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 bytes", "c3": "insert XID stamp"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 bytes", "c3": "delete XID stamp"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 bytes", "c3": "insert and/or delete CID stamp (overlays with t_xvac)"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 bytes", "c3": "XID for VACUUM operation moving a row version"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 bytes", "c3": "current TID of this or newer row version"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 bytes", "c3": "number of attributes, plus various flag bits"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 bytes", "c3": "various flag bits"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 byte", "c3": "offset to user data"}], "title": "HeapTupleHeaderData Layout", "columns": [{"key": "c0", "label": "Field"}, {"key": "c1", "label": "Type"}, {"key": "c2", "label": "Length"}, {"key": "c3", "label": "Description"}]}]}, "comparison_hash": "7f6e968716966dae8869d6c14f0a6aa229d745d4d4bde899b61eeec58c8d7ea0", "manual_language": "zh", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a069.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u603b\u5171\u4e3a t_natts \u4f4d\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a069.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "12": {"facts": [], "tables": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "related": [], "release": {"ref": "https://ftp.postgresql.org/pub/source/v12.22/postgresql-12.22.tar.bz2", "label": "12.22", "major": "12", "channel": "stable", "revision": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, "sources": [{"url": "/docs/12/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "path": "storage-page-layout.html", "label": "PostgreSQL 12 English manual", "sha256": "f485389ef7d0b5fd0a2ba4d0199308aac99fa413f8bdca01c3dab726841ee224"}], "zh_from": {"kind": "same-version-chinese-manual-with-source-derived-identity", "manual": {"url": "/zh/docs/12/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "anchor": "STORAGE-TUPLE-LAYOUT", "locale": "zh-Hans", "version": "12", "build_id": 65, "page_key": "storage-page-layout.html", "extraction": "concept-introduction", "source_hash": "3cc93e63844cdbe7334fc1e9124fba844e5baa971775b04f93ca30e8d738ad5b", "fragment_sha256": "99c6732cb099949b0752dc8b573342492e626f5d7bff747ccaf96a19131dbd90", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "snapshot:sha256:86d2ff781f93e1de17122ebc514d5e64fcb63fed15941f496d7e146c6dcc7a49", "translated_from_revision": null}, "body_sha256": "85367240a668b98d8abdde923678f535f46508641c3c9568e124d02ae4b519d7", "runtime_rerun": false, "authored_translation": "source-derived-identity", "source_facts_revision": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, "facts_zh": [], "sections": [], "center_zh": {"title": "Table row layout", "locale": "zh-Hans", "source": {"key": "tuple-layout", "locale": "zh-Hans", "version": "12", "text_hash": "f1973f015d3e246c66ca6857029caeb47a0d0275ca02c0429f858bdf323c7d0a", "collection": "storage", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, "payload": {"facts": [], "tables": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-source-derived-identity", "manual": {"url": "/zh/docs/12/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "anchor": "STORAGE-TUPLE-LAYOUT", "locale": "zh-Hans", "version": "12", "build_id": 65, "page_key": "storage-page-layout.html", "extraction": "concept-introduction", "source_hash": "3cc93e63844cdbe7334fc1e9124fba844e5baa971775b04f93ca30e8d738ad5b", "fragment_sha256": "99c6732cb099949b0752dc8b573342492e626f5d7bff747ccaf96a19131dbd90", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "snapshot:sha256:86d2ff781f93e1de17122ebc514d5e64fcb63fed15941f496d7e146c6dcc7a49", "translated_from_revision": null}, "body_sha256": "85367240a668b98d8abdde923678f535f46508641c3c9568e124d02ae4b519d7", "runtime_rerun": false, "authored_translation": "source-derived-identity", "source_facts_revision": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, "sections": [], "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 69.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 69.2 \u8282 ", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a069.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a069.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "summary": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 69.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 69.2 \u8282 ", "version": "12", "link_map": {"/zh/docs/12/storage-toast.html": "/docs/12/storage-toast.html", "/zh/docs/12/storage-page-layout.html#STORAGE-TUPLE-LAYOUT": "/docs/12/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "/zh/docs/12/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE": "/docs/12/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE"}, "body_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a069.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a069.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

", "body_sha256": "1a3261176117b9752554eb607678fdf53ddc78b86221ba5a02327b6544cfdf1f", "content_hash": "f1973f015d3e246c66ca6857029caeb47a0d0275ca02c0429f858bdf323c7d0a", "source_database": "center", "source_revision": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, "signature": "", "tables_zh": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "description": ["\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 69.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 69.2 \u8282 "], "manual_html": "", "manual_path": "/docs/12/storage-page-layout.html", "sections_zh": [], "localization": {"status": "complete", "sources": [{"url": "/docs/12/storage-page-layout.html", "method": "same-major semantic node", "sha256": "f61914805748cb00cfee1c774b88cde0c23c3383ac638b65752b83955e547bb3", "language": "zh", "matched_nodes": ["#STORAGE-PAGE-LAYOUT/div[18]/div[2]/p[0]", "#STORAGE-PAGE-LAYOUT/div[18]/p[1]", "#STORAGE-PAGE-LAYOUT/div[18]/p[4]", "#STORAGE-PAGE-LAYOUT/div[18]/p[5]", "#STORAGE-PAGE-LAYOUT/div[18]/p[6]", "#STORAGE-PAGE-LAYOUT/div[1]"]}], "language": "zh", "original_text": {"/versions/12/description/0": "Physical row headers, null bitmap, alignment and column data.", "/versions/12/tables/0/title": "HeapTupleHeaderData Layout", "/versions/12/tables/0/rows/0/c2": "4 bytes", "/versions/12/tables/0/rows/0/c3": "insert XID stamp", "/versions/12/tables/0/rows/1/c2": "4 bytes", "/versions/12/tables/0/rows/1/c3": "delete XID stamp", "/versions/12/tables/0/rows/2/c2": "4 bytes", "/versions/12/tables/0/rows/2/c3": "insert and/or delete CID stamp (overlays with t_xvac)", "/versions/12/tables/0/rows/3/c2": "4 bytes", "/versions/12/tables/0/rows/3/c3": "XID for VACUUM operation moving a row version", "/versions/12/tables/0/rows/4/c2": "6 bytes", "/versions/12/tables/0/rows/4/c3": "current TID of this or newer row version", "/versions/12/tables/0/rows/5/c2": "2 bytes", "/versions/12/tables/0/rows/5/c3": "number of attributes, plus various flag bits", "/versions/12/tables/0/rows/6/c2": "2 bytes", "/versions/12/tables/0/rows/6/c3": "various flag bits", "/versions/12/tables/0/rows/7/c2": "1 byte", "/versions/12/tables/0/rows/7/c3": "offset to user data", "/versions/12/tables/0/columns/0/label": "Field", "/versions/12/tables/0/columns/1/label": "Type", "/versions/12/tables/0/columns/2/label": "Length", "/versions/12/tables/0/columns/3/label": "Description"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "a5c44cc3663427e859decc93b65080728fabdcead5ac47262e5c0c42caac465c", "canonical_center_text_hash": "f1973f015d3e246c66ca6857029caeb47a0d0275ca02c0429f858bdf323c7d0a"}, "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 69.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 69.2 \u8282 ", "comparison_data": {"layouts": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 bytes", "c3": "insert XID stamp"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 bytes", "c3": "delete XID stamp"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 bytes", "c3": "insert and/or delete CID stamp (overlays with t_xvac)"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 bytes", "c3": "XID for VACUUM operation moving a row version"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 bytes", "c3": "current TID of this or newer row version"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 bytes", "c3": "number of attributes, plus various flag bits"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 bytes", "c3": "various flag bits"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 byte", "c3": "offset to user data"}], "title": "HeapTupleHeaderData Layout", "columns": [{"key": "c0", "label": "Field"}, {"key": "c1", "label": "Type"}, {"key": "c2", "label": "Length"}, {"key": "c3", "label": "Description"}]}]}, "comparison_hash": "7f6e968716966dae8869d6c14f0a6aa229d745d4d4bde899b61eeec58c8d7ea0", "manual_language": "zh", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a069.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a069.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "13": {"facts": [], "tables": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": 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"ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-source-derived-identity", "manual": {"url": "/zh/docs/13/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "anchor": "STORAGE-TUPLE-LAYOUT", "locale": "zh-Hans", "version": "13", "build_id": 66, "page_key": "storage-page-layout.html", "extraction": "concept-introduction", "source_hash": "fcbfe7625f40522324a335ccf94df452400b4ba5d42040d397728fe773004f7b", "fragment_sha256": "307d7e4bb4b2d2bebd0956fd5a058b9f10c14860685e70893191ea2d64b67c7a", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "snapshot:sha256:a13a825c39f0268ef1cfe9137e283e38d0da73b2d7894f0733c7b26372a4f6a4", "translated_from_revision": null}, "body_sha256": "71c0298a9e63facc01ca241aa18a6956e2df722d1d8c4d4da3f59ceee5d011a0", "runtime_rerun": false, "authored_translation": "source-derived-identity", "source_facts_revision": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6"}, "sections": [], "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 69.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 69.2 \u8282 ", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a069.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a069.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "summary": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 69.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 69.2 \u8282 ", "version": "13", "link_map": {"/zh/docs/13/storage-toast.html": "/docs/13/storage-toast.html", "/zh/docs/13/storage-page-layout.html#STORAGE-TUPLE-LAYOUT": "/docs/13/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "/zh/docs/13/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE": "/docs/13/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE"}, "body_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a069.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a069.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

", "body_sha256": "2d6b4f9eeda37462bd7c6029f94a0771db20c63de4dd18b57c2852ad9875945d", "content_hash": "0ee5a6becbcd9bbe0c382ea51620bbd513bfa1af34d8513c96c94188aceb9499", "source_database": "center", "source_revision": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6"}, "signature": "", "tables_zh": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "description": ["\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 69.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 69.2 \u8282 "], "manual_html": "", "manual_path": "/docs/13/storage-page-layout.html", "sections_zh": [], "localization": {"status": "complete", "sources": [{"url": "/docs/13/storage-page-layout.html", "method": "same-major semantic node", "sha256": "8f345d33cebccf663d12f0103dacc41820cd492d575b5faf6bcab66832f8ba39", "language": "zh", "matched_nodes": ["#STORAGE-PAGE-LAYOUT/div[18]/div[2]/p[0]", "#STORAGE-PAGE-LAYOUT/div[18]/p[1]", "#STORAGE-PAGE-LAYOUT/div[18]/p[4]", "#STORAGE-PAGE-LAYOUT/div[18]/p[5]", "#STORAGE-PAGE-LAYOUT/div[18]/p[6]", "#STORAGE-PAGE-LAYOUT/div[1]"]}], "language": "zh", "original_text": {"/versions/13/description/0": "Physical row headers, null bitmap, alignment and column data.", "/versions/13/tables/0/title": "HeapTupleHeaderData Layout", "/versions/13/tables/0/rows/0/c2": "4 bytes", "/versions/13/tables/0/rows/0/c3": "insert XID stamp", "/versions/13/tables/0/rows/1/c2": "4 bytes", "/versions/13/tables/0/rows/1/c3": "delete XID stamp", "/versions/13/tables/0/rows/2/c2": "4 bytes", "/versions/13/tables/0/rows/2/c3": "insert and/or delete CID stamp (overlays with t_xvac)", "/versions/13/tables/0/rows/3/c2": "4 bytes", "/versions/13/tables/0/rows/3/c3": "XID for VACUUM operation moving a row version", "/versions/13/tables/0/rows/4/c2": "6 bytes", "/versions/13/tables/0/rows/4/c3": "current TID of this or newer row version", "/versions/13/tables/0/rows/5/c2": "2 bytes", "/versions/13/tables/0/rows/5/c3": "number of attributes, plus various flag bits", "/versions/13/tables/0/rows/6/c2": "2 bytes", "/versions/13/tables/0/rows/6/c3": "various flag bits", "/versions/13/tables/0/rows/7/c2": "1 byte", "/versions/13/tables/0/rows/7/c3": "offset to user data", "/versions/13/tables/0/columns/0/label": "Field", "/versions/13/tables/0/columns/1/label": "Type", "/versions/13/tables/0/columns/2/label": "Length", "/versions/13/tables/0/columns/3/label": "Description"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "fc10a09e400447404e8c89c11d152dcde3eb1df0d2d6acd682b1f57cab45eb21", "canonical_center_text_hash": "0ee5a6becbcd9bbe0c382ea51620bbd513bfa1af34d8513c96c94188aceb9499"}, "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 69.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 69.2 \u8282 ", "comparison_data": {"layouts": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 bytes", "c3": "insert XID stamp"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 bytes", "c3": "delete XID stamp"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 bytes", "c3": "insert and/or delete CID stamp (overlays with t_xvac)"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 bytes", "c3": "XID for VACUUM operation moving a row version"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 bytes", "c3": "current TID of this or newer row version"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 bytes", "c3": "number of attributes, plus various flag bits"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 bytes", "c3": "various flag bits"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 byte", "c3": "offset to user data"}], "title": "HeapTupleHeaderData Layout", "columns": [{"key": "c0", "label": "Field"}, {"key": "c1", "label": "Type"}, {"key": "c2", "label": "Length"}, {"key": "c3", "label": "Description"}]}]}, "comparison_hash": "7f6e968716966dae8869d6c14f0a6aa229d745d4d4bde899b61eeec58c8d7ea0", "manual_language": "zh", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a069.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a069.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "14": {"facts": [], "tables": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "related": [], "release": {"ref": "https://ftp.postgresql.org/pub/source/v14.24/postgresql-14.24.tar.bz2", "label": "14.24", "major": "14", "channel": "stable", "revision": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, "sources": [{"url": "/docs/14/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "path": "storage-page-layout.html", "label": "PostgreSQL 14 English manual", "sha256": "0086151fad97655a71308a5389066374e3e178c423cb855b4084e7a2c3b078c5"}], "zh_from": {"kind": "same-version-chinese-manual-with-source-derived-identity", "manual": {"url": 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{"key": "tuple-layout", "locale": "zh-Hans", "version": "14", "text_hash": "1e4281875cbf72ee6e2c4694c7c26cc39ddcf5530fc877342021aa87e89ea521", "collection": "storage", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, "payload": {"facts": [], "tables": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-source-derived-identity", "manual": {"url": "/zh/docs/14/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "anchor": "STORAGE-TUPLE-LAYOUT", "locale": "zh-Hans", "version": "14", "build_id": 99, "page_key": "storage-page-layout.html", "extraction": "concept-introduction", "source_hash": "8a32af698668a200a4d74e19d629b93fef645528e97fe599521760691245921b", "fragment_sha256": "178b5ffd1fc0ebc793bcb4f46965acad2d3250b0ebb07bcf6f32f04a48f5d36b", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:87e6aa4fd6e1ec85c5f4a6de4f5647cfd9e5de734ca2c266d32b6d6192c662ef", "translated_from_revision": null}, "body_sha256": "ed091061118a763bb8af24a1ec6b8895402f31efd7f8c0c877c6328795740ea3", "runtime_rerun": false, "authored_translation": "source-derived-identity", "source_facts_revision": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, "sections": [], "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 70.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 70.2 \u8282 ", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a070.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a070.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "summary": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 70.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 70.2 \u8282 ", "version": "14", "link_map": {"/zh/docs/14/storage-toast.html": "/docs/14/storage-toast.html", "/zh/docs/14/storage-page-layout.html#STORAGE-TUPLE-LAYOUT": "/docs/14/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "/zh/docs/14/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE": "/docs/14/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE"}, "body_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a070.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a070.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

", "body_sha256": "a6b1142d76d8c80cf1aff876c26937f26e5f2e5541c79441a6bb8db123864005", "content_hash": "1e4281875cbf72ee6e2c4694c7c26cc39ddcf5530fc877342021aa87e89ea521", "source_database": "center", "source_revision": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, "signature": "", "tables_zh": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "description": ["\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 70.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 70.2 \u8282 "], "manual_html": "", "manual_path": "/docs/14/storage-page-layout.html", "sections_zh": [], "localization": {"status": "complete", "sources": [{"url": "/docs/14/storage-page-layout.html", "method": "same-major semantic node", "sha256": "715a2f826a4e1ec9a3eae2da9e5746928bdaf5a5b7e05ee60ed9eedf4ab90747", "language": "zh", "matched_nodes": ["#STORAGE-PAGE-LAYOUT/div[18]/div[2]/p[0]", "#STORAGE-PAGE-LAYOUT/div[18]/p[1]", "#STORAGE-PAGE-LAYOUT/div[18]/p[4]", "#STORAGE-PAGE-LAYOUT/div[18]/p[5]", "#STORAGE-PAGE-LAYOUT/div[18]/p[6]", "#STORAGE-PAGE-LAYOUT/div[1]"]}], "language": "zh", "original_text": {"/versions/14/description/0": "Physical row headers, null bitmap, alignment and column data.", "/versions/14/tables/0/title": "HeapTupleHeaderData Layout", "/versions/14/tables/0/rows/0/c2": "4 bytes", "/versions/14/tables/0/rows/0/c3": "insert XID stamp", "/versions/14/tables/0/rows/1/c2": "4 bytes", "/versions/14/tables/0/rows/1/c3": "delete XID stamp", "/versions/14/tables/0/rows/2/c2": "4 bytes", "/versions/14/tables/0/rows/2/c3": "insert and/or delete CID stamp (overlays with t_xvac)", "/versions/14/tables/0/rows/3/c2": "4 bytes", "/versions/14/tables/0/rows/3/c3": "XID for VACUUM operation moving a row version", "/versions/14/tables/0/rows/4/c2": "6 bytes", "/versions/14/tables/0/rows/4/c3": "current TID of this or newer row version", "/versions/14/tables/0/rows/5/c2": "2 bytes", "/versions/14/tables/0/rows/5/c3": "number of attributes, plus various flag bits", "/versions/14/tables/0/rows/6/c2": "2 bytes", "/versions/14/tables/0/rows/6/c3": "various flag bits", "/versions/14/tables/0/rows/7/c2": "1 byte", "/versions/14/tables/0/rows/7/c3": "offset to user data", "/versions/14/tables/0/columns/0/label": "Field", "/versions/14/tables/0/columns/1/label": "Type", "/versions/14/tables/0/columns/2/label": "Length", "/versions/14/tables/0/columns/3/label": "Description"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "424eb32b16be0b88ef5927168b40e768999cdc14916b17e4189b54d55e07a824", "canonical_center_text_hash": "1e4281875cbf72ee6e2c4694c7c26cc39ddcf5530fc877342021aa87e89ea521"}, "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 70.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 70.2 \u8282 ", "comparison_data": {"layouts": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 bytes", "c3": "insert XID stamp"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 bytes", "c3": "delete XID stamp"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 bytes", "c3": "insert and/or delete CID stamp (overlays with t_xvac)"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 bytes", "c3": "XID for VACUUM operation moving a row version"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 bytes", "c3": "current TID of this or newer row version"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 bytes", "c3": "number of attributes, plus various flag bits"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 bytes", "c3": "various flag bits"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 byte", "c3": "offset to user data"}], "title": "HeapTupleHeaderData Layout", "columns": [{"key": "c0", "label": "Field"}, {"key": "c1", "label": "Type"}, {"key": "c2", "label": "Length"}, {"key": "c3", "label": "Description"}]}]}, "comparison_hash": "7f6e968716966dae8869d6c14f0a6aa229d745d4d4bde899b61eeec58c8d7ea0", "manual_language": "zh", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a070.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a070.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "15": {"facts": [], "tables": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": 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"t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-source-derived-identity", "manual": {"url": "/zh/docs/15/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "anchor": "STORAGE-TUPLE-LAYOUT", "locale": "zh-Hans", "version": "15", "build_id": 101, "page_key": "storage-page-layout.html", "extraction": "concept-introduction", "source_hash": "b52478b89edd91bb6162f45dad8afd2c9b126315c9dac17fc704e26431844249", "fragment_sha256": "c4bdabf5a9a59a6da79a59fb9d3262e6937cc2f8266be8fa8398d8f364c619bd", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:6bce1a2df9170cb1146a1411c5547190856638221a6539e618ee1016c9f493ad", "translated_from_revision": null}, "body_sha256": "ea045862fa4a1d8a7674ea049cc0b82706bffe55b40890c047319647b9c211f1", "runtime_rerun": false, "authored_translation": "source-derived-identity", "source_facts_revision": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}, "sections": [], "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 73.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 73.2 \u8282 ", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a073.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a073.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "summary": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 73.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 73.2 \u8282 ", "version": "15", "link_map": {"/zh/docs/15/storage-toast.html": "/docs/15/storage-toast.html", "/zh/docs/15/storage-page-layout.html#STORAGE-TUPLE-LAYOUT": "/docs/15/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "/zh/docs/15/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE": "/docs/15/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE"}, "body_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a073.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a073.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

", "body_sha256": "b3633f10c5ea0b3027f7537b2990e52b5c6612e0284283ecd6e077968fe949f4", "content_hash": "5f9c2bb665057afd687fd0d53e001113a2142318205953af35fb5e2b3484669e", "source_database": "center", "source_revision": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}, "signature": "", "tables_zh": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "description": ["\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 73.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 73.2 \u8282 "], "manual_html": "", "manual_path": "/docs/15/storage-page-layout.html", "sections_zh": [], "localization": {"status": "complete", "sources": [{"url": "/docs/15/storage-page-layout.html", "method": "same-major semantic node", "sha256": "2c2602d84ed184bdd78e6473fd991c8f64d4e6921371324f0d349f423eba5718", "language": "zh", "matched_nodes": ["#STORAGE-PAGE-LAYOUT/div[18]/div[2]/p[0]", "#STORAGE-PAGE-LAYOUT/div[18]/p[1]", "#STORAGE-PAGE-LAYOUT/div[18]/p[4]", "#STORAGE-PAGE-LAYOUT/div[18]/p[5]", "#STORAGE-PAGE-LAYOUT/div[18]/p[6]", "#STORAGE-PAGE-LAYOUT/div[1]"]}], "language": "zh", "original_text": {"/versions/15/description/0": "Physical row headers, null bitmap, alignment and column data.", "/versions/15/tables/0/title": "HeapTupleHeaderData Layout", "/versions/15/tables/0/rows/0/c2": "4 bytes", "/versions/15/tables/0/rows/0/c3": "insert XID stamp", "/versions/15/tables/0/rows/1/c2": "4 bytes", "/versions/15/tables/0/rows/1/c3": "delete XID stamp", "/versions/15/tables/0/rows/2/c2": "4 bytes", "/versions/15/tables/0/rows/2/c3": "insert and/or delete CID stamp (overlays with t_xvac)", "/versions/15/tables/0/rows/3/c2": "4 bytes", "/versions/15/tables/0/rows/3/c3": "XID for VACUUM operation moving a row version", "/versions/15/tables/0/rows/4/c2": "6 bytes", "/versions/15/tables/0/rows/4/c3": "current TID of this or newer row version", "/versions/15/tables/0/rows/5/c2": "2 bytes", "/versions/15/tables/0/rows/5/c3": "number of attributes, plus various flag bits", "/versions/15/tables/0/rows/6/c2": "2 bytes", "/versions/15/tables/0/rows/6/c3": "various flag bits", "/versions/15/tables/0/rows/7/c2": "1 byte", "/versions/15/tables/0/rows/7/c3": "offset to user data", "/versions/15/tables/0/columns/0/label": "Field", "/versions/15/tables/0/columns/1/label": "Type", "/versions/15/tables/0/columns/2/label": "Length", "/versions/15/tables/0/columns/3/label": "Description"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "377d9d40632562901f2602b55d9f6866bd5d04ce81bc4dbb5f0a65ee9172a542", "canonical_center_text_hash": "5f9c2bb665057afd687fd0d53e001113a2142318205953af35fb5e2b3484669e"}, "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 73.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 73.2 \u8282 ", "comparison_data": {"layouts": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 bytes", "c3": "insert XID stamp"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 bytes", "c3": "delete XID stamp"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 bytes", "c3": "insert and/or delete CID stamp (overlays with t_xvac)"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 bytes", "c3": "XID for VACUUM operation moving a row version"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 bytes", "c3": "current TID of this or newer row version"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 bytes", "c3": "number of attributes, plus various flag bits"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 bytes", "c3": "various flag bits"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 byte", "c3": "offset to user data"}], "title": "HeapTupleHeaderData Layout", "columns": [{"key": "c0", "label": "Field"}, {"key": "c1", "label": "Type"}, {"key": "c2", "label": "Length"}, {"key": "c3", "label": "Description"}]}]}, "comparison_hash": "7f6e968716966dae8869d6c14f0a6aa229d745d4d4bde899b61eeec58c8d7ea0", "manual_language": "zh", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a073.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a073.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "16": {"facts": [], "tables": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "related": [], "release": {"ref": "https://ftp.postgresql.org/pub/source/v16.15/postgresql-16.15.tar.bz2", "label": "16.15", "major": "16", "channel": "stable", "revision": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, "sources": [{"url": "/docs/16/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "path": "storage-page-layout.html", "label": "PostgreSQL 16 English manual", "sha256": "8575d1a8e8bb10ffdccc043783fce8d53e59bd6e98f1cd66b3761a90d4d77c27"}], "zh_from": {"kind": "same-version-chinese-manual-with-source-derived-identity", "manual": {"url": "/zh/docs/16/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "anchor": "STORAGE-TUPLE-LAYOUT", "locale": "zh-Hans", "version": "16", "build_id": 103, "page_key": "storage-page-layout.html", "extraction": "concept-introduction", "source_hash": "1a184973f783f9785e92ba1c67b036e2035e51a6055214696bde0c03730f2ef7", "fragment_sha256": "9a47941156247ba667d3c861e7426e687f606860750c72a8814e1946dbd451e7", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:80579a071736780f9c4022bb5148e1fb1256f1a33591306af67816e9e9bf3a9b", "translated_from_revision": null}, "body_sha256": "507bf1b4e444ea75bd993c4c53d804ff15d95691e3ede8bd7e2e812dd936b2e0", "runtime_rerun": false, "authored_translation": "source-derived-identity", "source_facts_revision": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, "facts_zh": [], "sections": [], "center_zh": {"title": "Table row layout", "locale": "zh-Hans", "source": {"key": "tuple-layout", "locale": "zh-Hans", "version": "16", "text_hash": "0997f7020929d25715f2257ad0493302d04a6257ea94c8129f5730af7ee58327", "collection": "storage", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, "payload": {"facts": [], "tables": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-source-derived-identity", "manual": {"url": "/zh/docs/16/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "anchor": "STORAGE-TUPLE-LAYOUT", "locale": "zh-Hans", "version": "16", "build_id": 103, "page_key": "storage-page-layout.html", "extraction": "concept-introduction", "source_hash": "1a184973f783f9785e92ba1c67b036e2035e51a6055214696bde0c03730f2ef7", "fragment_sha256": "9a47941156247ba667d3c861e7426e687f606860750c72a8814e1946dbd451e7", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:80579a071736780f9c4022bb5148e1fb1256f1a33591306af67816e9e9bf3a9b", "translated_from_revision": null}, "body_sha256": "507bf1b4e444ea75bd993c4c53d804ff15d95691e3ede8bd7e2e812dd936b2e0", "runtime_rerun": false, "authored_translation": "source-derived-identity", "source_facts_revision": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, "sections": [], "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 73.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 73.2 \u8282 ", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a073.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a073.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "summary": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 73.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 73.2 \u8282 ", "version": "16", "link_map": {"/zh/docs/16/storage-toast.html": "/docs/16/storage-toast.html", "/zh/docs/16/storage-page-layout.html#STORAGE-TUPLE-LAYOUT": "/docs/16/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "/zh/docs/16/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE": "/docs/16/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE"}, "body_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a073.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a073.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

", "body_sha256": "951bcc96d88fcdf2046b733daaa36b8778c811a567c968cb3ca622019aae5ebc", "content_hash": "0997f7020929d25715f2257ad0493302d04a6257ea94c8129f5730af7ee58327", "source_database": "center", "source_revision": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, "signature": "", "tables_zh": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "description": ["\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 73.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 73.2 \u8282 "], "manual_html": "", "manual_path": "/docs/16/storage-page-layout.html", "sections_zh": [], "localization": {"status": "complete", "sources": [{"url": "/docs/16/storage-page-layout.html", "method": "same-major semantic node", "sha256": "bf698675faf9fb84f4a709e4067ed25bc2ecbc55b98c2ea893349308b5af9d43", "language": "zh", "matched_nodes": ["#STORAGE-PAGE-LAYOUT/div[18]/div[2]/p[0]", "#STORAGE-PAGE-LAYOUT/div[18]/p[1]", "#STORAGE-PAGE-LAYOUT/div[18]/p[4]", "#STORAGE-PAGE-LAYOUT/div[18]/p[5]", "#STORAGE-PAGE-LAYOUT/div[18]/p[6]", "#STORAGE-PAGE-LAYOUT/div[1]"]}], "language": "zh", "original_text": {"/versions/16/description/0": "Physical row headers, null bitmap, alignment and column data.", "/versions/16/tables/0/title": "HeapTupleHeaderData Layout", "/versions/16/tables/0/rows/0/c2": "4 bytes", "/versions/16/tables/0/rows/0/c3": "insert XID stamp", "/versions/16/tables/0/rows/1/c2": "4 bytes", "/versions/16/tables/0/rows/1/c3": "delete XID stamp", "/versions/16/tables/0/rows/2/c2": "4 bytes", "/versions/16/tables/0/rows/2/c3": "insert and/or delete CID stamp (overlays with t_xvac)", "/versions/16/tables/0/rows/3/c2": "4 bytes", "/versions/16/tables/0/rows/3/c3": "XID for VACUUM operation moving a row version", "/versions/16/tables/0/rows/4/c2": "6 bytes", "/versions/16/tables/0/rows/4/c3": "current TID of this or newer row version", "/versions/16/tables/0/rows/5/c2": "2 bytes", "/versions/16/tables/0/rows/5/c3": "number of attributes, plus various flag bits", "/versions/16/tables/0/rows/6/c2": "2 bytes", "/versions/16/tables/0/rows/6/c3": "various flag bits", "/versions/16/tables/0/rows/7/c2": "1 byte", "/versions/16/tables/0/rows/7/c3": "offset to user data", "/versions/16/tables/0/columns/0/label": "Field", "/versions/16/tables/0/columns/1/label": "Type", "/versions/16/tables/0/columns/2/label": "Length", "/versions/16/tables/0/columns/3/label": "Description"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "4bb0403b362db23df0870a560b6e09037a75b65060f1300af0378eeefec525bc", "canonical_center_text_hash": "0997f7020929d25715f2257ad0493302d04a6257ea94c8129f5730af7ee58327"}, "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 73.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 73.2 \u8282 ", "comparison_data": {"layouts": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 bytes", "c3": "insert XID stamp"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 bytes", "c3": "delete XID stamp"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 bytes", "c3": "insert and/or delete CID stamp (overlays with t_xvac)"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 bytes", "c3": "XID for VACUUM operation moving a row version"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 bytes", "c3": "current TID of this or newer row version"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 bytes", "c3": "number of attributes, plus various flag bits"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 bytes", "c3": "various flag bits"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 byte", "c3": "offset to user data"}], "title": "HeapTupleHeaderData Layout", "columns": [{"key": "c0", "label": "Field"}, {"key": "c1", "label": "Type"}, {"key": "c2", "label": "Length"}, {"key": "c3", "label": "Description"}]}]}, "comparison_hash": "7f6e968716966dae8869d6c14f0a6aa229d745d4d4bde899b61eeec58c8d7ea0", "manual_language": "zh", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a073.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a073.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "17": {"facts": [], "tables": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": 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"t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-source-derived-identity", "manual": {"url": "/zh/docs/17/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "anchor": "STORAGE-TUPLE-LAYOUT", "locale": "zh-Hans", "version": "17", "build_id": 105, "page_key": "storage-page-layout.html", "extraction": "concept-introduction", "source_hash": "a0e28f2f86bbde1652251bbbe0976ee538ffcb4666a91aadbd63007a22455477", "fragment_sha256": "43de7919635f2101c20089282f62b766bc16a362b16ecd6d7266149799f42660", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:7340767258d21c21b36f373f1fff6bab2be18e0daca13a865129db6105c09efd", "translated_from_revision": null}, "body_sha256": "f1e864096d56633a219ba3de6d5cd81050b4f575618d61c6c61587506d7d99f3", "runtime_rerun": false, "authored_translation": "source-derived-identity", "source_facts_revision": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, "sections": [], "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 65.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 65.2 \u8282 ", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a065.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a065.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "summary": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 65.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 65.2 \u8282 ", "version": "17", "link_map": {"/zh/docs/17/storage-toast.html": "/docs/17/storage-toast.html", "/zh/docs/17/storage-page-layout.html#STORAGE-TUPLE-LAYOUT": "/docs/17/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "/zh/docs/17/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE": "/docs/17/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE"}, "body_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a065.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a065.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

", "body_sha256": "5b5a9de39c58b42e33f914661b292fce846cc0b8954a09833aeb5d24b53cd1a3", "content_hash": "5b0bc5611fdc70feab1c002a52196170b6234c4f9d12211a7466aa1c471e79e0", "source_database": "center", "source_revision": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, "signature": "", "tables_zh": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "description": ["\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 65.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 65.2 \u8282 "], "manual_html": "", "manual_path": "/docs/17/storage-page-layout.html", "sections_zh": [], "localization": {"status": "complete", "sources": [{"url": "/docs/17/storage-page-layout.html", "method": "same-major semantic node", "sha256": "5f1706fce27c6505086f0b42549876c32ebaba985b000585c62535c69b933c3f", "language": "zh", "matched_nodes": ["#STORAGE-PAGE-LAYOUT/div[18]/div[2]/p[0]", "#STORAGE-PAGE-LAYOUT/div[18]/p[1]", "#STORAGE-PAGE-LAYOUT/div[18]/p[4]", "#STORAGE-PAGE-LAYOUT/div[18]/p[5]", "#STORAGE-PAGE-LAYOUT/div[18]/p[6]", "#STORAGE-PAGE-LAYOUT/div[1]"]}], "language": "zh", "original_text": {"/versions/17/description/0": "Physical row headers, null bitmap, alignment and column data.", "/versions/17/tables/0/title": "HeapTupleHeaderData Layout", "/versions/17/tables/0/rows/0/c2": "4 bytes", "/versions/17/tables/0/rows/0/c3": "insert XID stamp", "/versions/17/tables/0/rows/1/c2": "4 bytes", "/versions/17/tables/0/rows/1/c3": "delete XID stamp", "/versions/17/tables/0/rows/2/c2": "4 bytes", "/versions/17/tables/0/rows/2/c3": "insert and/or delete CID stamp (overlays with t_xvac)", "/versions/17/tables/0/rows/3/c2": "4 bytes", "/versions/17/tables/0/rows/3/c3": "XID for VACUUM operation moving a row version", "/versions/17/tables/0/rows/4/c2": "6 bytes", "/versions/17/tables/0/rows/4/c3": "current TID of this or newer row version", "/versions/17/tables/0/rows/5/c2": "2 bytes", "/versions/17/tables/0/rows/5/c3": "number of attributes, plus various flag bits", "/versions/17/tables/0/rows/6/c2": "2 bytes", "/versions/17/tables/0/rows/6/c3": "various flag bits", "/versions/17/tables/0/rows/7/c2": "1 byte", "/versions/17/tables/0/rows/7/c3": "offset to user data", "/versions/17/tables/0/columns/0/label": "Field", "/versions/17/tables/0/columns/1/label": "Type", "/versions/17/tables/0/columns/2/label": "Length", "/versions/17/tables/0/columns/3/label": "Description"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "de979b68aa0498108b1b653e3aa3c338110c1604fc040114a3988741b69dcac2", "canonical_center_text_hash": "5b0bc5611fdc70feab1c002a52196170b6234c4f9d12211a7466aa1c471e79e0"}, "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 65.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 65.2 \u8282 ", "comparison_data": {"layouts": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 bytes", "c3": "insert XID stamp"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 bytes", "c3": "delete XID stamp"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 bytes", "c3": "insert and/or delete CID stamp (overlays with t_xvac)"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 bytes", "c3": "XID for VACUUM operation moving a row version"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 bytes", "c3": "current TID of this or newer row version"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 bytes", "c3": "number of attributes, plus various flag bits"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 bytes", "c3": "various flag bits"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 byte", "c3": "offset to user data"}], "title": "HeapTupleHeaderData Layout", "columns": [{"key": "c0", "label": "Field"}, {"key": "c1", "label": "Type"}, {"key": "c2", "label": "Length"}, {"key": "c3", "label": "Description"}]}]}, "comparison_hash": "7f6e968716966dae8869d6c14f0a6aa229d745d4d4bde899b61eeec58c8d7ea0", "manual_language": "zh", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a065.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a065.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "18": {"facts": [], "tables": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "related": [], "release": {"ref": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "label": "18.6", "major": "18", "channel": "stable", "revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "sources": [{"url": "/docs/18/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "path": "storage-page-layout.html", "label": "PostgreSQL 18 English manual", "sha256": "0d9f99e4cef5ea0a6741a74cab87052b929f7001730853c85d5e60d72179d355"}], "zh_from": {"kind": "same-version-chinese-manual-with-source-derived-identity", "manual": {"url": "/zh/docs/18/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "anchor": "STORAGE-TUPLE-LAYOUT", "locale": "zh-Hans", "version": "18", "build_id": 107, "page_key": "storage-page-layout.html", "extraction": "concept-introduction", "source_hash": "07870df29bfc52d49b5aa3018212c94da48a0d9edea8d214a87d8aca0b5d55f2", "fragment_sha256": "dee1db58a987e1f5ffbc6afe554287351b32d7b3694112aa379057599b1b44f1", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:08e987a66af27b98444a8057c256314eafa13611a3fb9e888214fc436824244b", "translated_from_revision": null}, "body_sha256": "67dcd3c43a99523896736f539ec9da214a78606b0e56fda9bc28648357331d0c", "runtime_rerun": false, "authored_translation": "source-derived-identity", "source_facts_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "facts_zh": [], "sections": [], "center_zh": {"title": "Table row layout", "locale": "zh-Hans", "source": {"key": "tuple-layout", "locale": "zh-Hans", "version": "18", "text_hash": "1f70f56a410ed4477fede1cfed6593bf2950c4a15fe020c47ddb55a1f4f7f7f7", "collection": "storage", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "payload": {"facts": [], "tables": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-source-derived-identity", "manual": {"url": "/zh/docs/18/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "anchor": "STORAGE-TUPLE-LAYOUT", "locale": "zh-Hans", "version": "18", "build_id": 107, "page_key": "storage-page-layout.html", "extraction": "concept-introduction", "source_hash": "07870df29bfc52d49b5aa3018212c94da48a0d9edea8d214a87d8aca0b5d55f2", "fragment_sha256": "dee1db58a987e1f5ffbc6afe554287351b32d7b3694112aa379057599b1b44f1", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:08e987a66af27b98444a8057c256314eafa13611a3fb9e888214fc436824244b", "translated_from_revision": null}, "body_sha256": "67dcd3c43a99523896736f539ec9da214a78606b0e56fda9bc28648357331d0c", "runtime_rerun": false, "authored_translation": "source-derived-identity", "source_facts_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "sections": [], "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 66.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 ", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a066.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a066.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "summary": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 66.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 ", "version": "18", "link_map": {"/zh/docs/18/storage-toast.html": "/docs/18/storage-toast.html", "/zh/docs/18/storage-page-layout.html#STORAGE-TUPLE-LAYOUT": "/docs/18/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "/zh/docs/18/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE": "/docs/18/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE"}, "body_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a066.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a066.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

", "body_sha256": "fdb78139bd42903e18148f28126309adb9482eea686da6434524eeab15b0be78", "content_hash": "1f70f56a410ed4477fede1cfed6593bf2950c4a15fe020c47ddb55a1f4f7f7f7", "source_database": "center", "source_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "signature": "", "tables_zh": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "description": ["\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 66.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 "], "manual_html": "", "manual_path": "/docs/18/storage-page-layout.html", "sections_zh": [], "localization": {"status": "complete", "sources": [{"url": "/docs/18/storage-page-layout.html", "method": "same-major semantic node", "sha256": "e504ff90f2cabf6f71046d80f1cc8d49664ba2f2f4bce0ef26e955d6c5580ab2", "language": "zh", "matched_nodes": ["#STORAGE-PAGE-LAYOUT/div[18]/div[2]/p[0]", "#STORAGE-PAGE-LAYOUT/div[18]/p[1]", "#STORAGE-PAGE-LAYOUT/div[18]/p[4]", "#STORAGE-PAGE-LAYOUT/div[18]/p[5]", "#STORAGE-PAGE-LAYOUT/div[18]/p[6]", "#STORAGE-PAGE-LAYOUT/div[1]"]}], "language": "zh", "original_text": {"/versions/18/description/0": "Physical row headers, null bitmap, alignment and column data.", "/versions/18/tables/0/title": "HeapTupleHeaderData Layout", "/versions/18/tables/0/rows/0/c2": "4 bytes", "/versions/18/tables/0/rows/0/c3": "insert XID stamp", "/versions/18/tables/0/rows/1/c2": "4 bytes", "/versions/18/tables/0/rows/1/c3": "delete XID stamp", "/versions/18/tables/0/rows/2/c2": "4 bytes", "/versions/18/tables/0/rows/2/c3": "insert and/or delete CID stamp (overlays with t_xvac)", "/versions/18/tables/0/rows/3/c2": "4 bytes", "/versions/18/tables/0/rows/3/c3": "XID for VACUUM operation moving a row version", "/versions/18/tables/0/rows/4/c2": "6 bytes", "/versions/18/tables/0/rows/4/c3": "current TID of this or newer row version", "/versions/18/tables/0/rows/5/c2": "2 bytes", "/versions/18/tables/0/rows/5/c3": "number of attributes, plus various flag bits", "/versions/18/tables/0/rows/6/c2": "2 bytes", "/versions/18/tables/0/rows/6/c3": "various flag bits", "/versions/18/tables/0/rows/7/c2": "1 byte", "/versions/18/tables/0/rows/7/c3": "offset to user data", "/versions/18/tables/0/columns/0/label": "Field", "/versions/18/tables/0/columns/1/label": "Type", "/versions/18/tables/0/columns/2/label": "Length", "/versions/18/tables/0/columns/3/label": "Description"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "f0a44bd96ec79f5387e9c512ba7a6444f819cd1a32e4c0cdf82f78d6c9d7d5b2", "canonical_center_text_hash": "1f70f56a410ed4477fede1cfed6593bf2950c4a15fe020c47ddb55a1f4f7f7f7"}, "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 66.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 ", "comparison_data": {"layouts": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 bytes", "c3": "insert XID stamp"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 bytes", "c3": "delete XID stamp"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 bytes", "c3": "insert and/or delete CID stamp (overlays with t_xvac)"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 bytes", "c3": "XID for VACUUM operation moving a row version"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 bytes", "c3": "current TID of this or newer row version"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 bytes", "c3": "number of attributes, plus various flag bits"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 bytes", "c3": "various flag bits"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 byte", "c3": "offset to user data"}], "title": "HeapTupleHeaderData Layout", "columns": [{"key": "c0", "label": "Field"}, {"key": "c1", "label": "Type"}, {"key": "c2", "label": "Length"}, {"key": "c3", "label": "Description"}]}]}, "comparison_hash": "7f6e968716966dae8869d6c14f0a6aa229d745d4d4bde899b61eeec58c8d7ea0", "manual_language": "zh", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a066.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a066.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

", "center_zh_rendered": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a066.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a066.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "19": {"facts": [], "tables": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "related": [], "release": {"ref": "https://ftp.postgresql.org/pub/source/v19rc1/postgresql-19rc1.tar.bz2", "label": "19rc1", "major": "19", "channel": "preview", "revision": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, "sources": [{"url": "/docs/19/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "path": "storage-page-layout.html", "label": "PostgreSQL 19 English manual", "sha256": "a6b49290ffd898b445d6b422f22d8f07e039ff9147b3864d2e083619bbf899bc"}], "zh_from": {"kind": "same-version-chinese-manual-with-source-derived-identity", "manual": {"url": 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"facts_zh": [], "sections": [], "center_zh": {"title": "Table row layout", "locale": "zh-Hans", "source": {"key": "tuple-layout", "locale": "zh-Hans", "version": "19", "text_hash": "1d777ccd21989d4dcb44c42614e02f6112c6683cb84b36710f80e9536dee6b35", "collection": "storage", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, "payload": {"facts": [], "tables": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-source-derived-identity", "manual": {"url": "/zh/docs/19/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", 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"\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 66.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 \uff09\u3002", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a066.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a066.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "summary": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 66.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 \uff09\u3002", "version": "19", "link_map": {"/zh/docs/19/storage-toast.html": "/docs/19/storage-toast.html", "/zh/docs/19/storage-page-layout.html#STORAGE-TUPLE-LAYOUT": "/docs/19/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "/zh/docs/19/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE": "/docs/19/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE"}, "body_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a066.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a066.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

", "body_sha256": "79366da39df1afe97545a83e32c5f3aad6e9222ea0e3ea2091294dd912639fa9", "content_hash": "1d777ccd21989d4dcb44c42614e02f6112c6683cb84b36710f80e9536dee6b35", "source_database": "center", "source_revision": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, "signature": "", "tables_zh": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "description": ["\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 66.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 \uff09\u3002"], "manual_html": "", "manual_path": "/docs/19/storage-page-layout.html", "sections_zh": [], "localization": {"status": "complete", "sources": [{"url": "/docs/19/storage-page-layout.html", "method": "same-major semantic node", "sha256": "449d5df50770072a5159075c211dd18f895edeaeb7ea22ba5936d469b017017c", "language": "zh", "matched_nodes": ["#STORAGE-PAGE-LAYOUT/div[18]/div[2]/p[0]", "#STORAGE-PAGE-LAYOUT/div[18]/p[1]", "#STORAGE-PAGE-LAYOUT/div[18]/p[4]", "#STORAGE-PAGE-LAYOUT/div[18]/p[5]", "#STORAGE-PAGE-LAYOUT/div[18]/p[6]", "#STORAGE-PAGE-LAYOUT/div[1]"]}], "language": "zh", "original_text": {"/versions/19/description/0": "Physical row headers, null bitmap, alignment and column data.", "/versions/19/tables/0/title": "HeapTupleHeaderData Layout", "/versions/19/tables/0/rows/0/c2": "4 bytes", "/versions/19/tables/0/rows/0/c3": "insert XID stamp", "/versions/19/tables/0/rows/1/c2": "4 bytes", "/versions/19/tables/0/rows/1/c3": "delete XID stamp", "/versions/19/tables/0/rows/2/c2": "4 bytes", "/versions/19/tables/0/rows/2/c3": "insert and/or delete CID stamp (overlays with t_xvac)", "/versions/19/tables/0/rows/3/c2": "4 bytes", "/versions/19/tables/0/rows/3/c3": "XID for VACUUM operation moving a row version", "/versions/19/tables/0/rows/4/c2": "6 bytes", "/versions/19/tables/0/rows/4/c3": "current TID of this or newer row version", "/versions/19/tables/0/rows/5/c2": "2 bytes", "/versions/19/tables/0/rows/5/c3": "number of attributes, plus various flag bits", "/versions/19/tables/0/rows/6/c2": "2 bytes", "/versions/19/tables/0/rows/6/c3": "various flag bits", "/versions/19/tables/0/rows/7/c2": "1 byte", "/versions/19/tables/0/rows/7/c3": "offset to user data", "/versions/19/tables/0/columns/0/label": "Field", "/versions/19/tables/0/columns/1/label": "Type", "/versions/19/tables/0/columns/2/label": "Length", "/versions/19/tables/0/columns/3/label": "Description"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "7ab94bd5f8a7ff7760f32152448a2c90b8db557e4eb97df768f597e53e7c5551", "canonical_center_text_hash": "1d777ccd21989d4dcb44c42614e02f6112c6683cb84b36710f80e9536dee6b35"}, "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 66.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 \uff09\u3002", "comparison_data": {"layouts": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 bytes", "c3": "insert XID stamp"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 bytes", "c3": "delete XID stamp"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 bytes", "c3": "insert and/or delete CID stamp (overlays with t_xvac)"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 bytes", "c3": "XID for VACUUM operation moving a row version"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 bytes", "c3": "current TID of this or newer row version"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 bytes", "c3": "number of attributes, plus various flag bits"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 bytes", "c3": "various flag bits"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 byte", "c3": "offset to user data"}], "title": "HeapTupleHeaderData Layout", "columns": [{"key": "c0", "label": "Field"}, {"key": "c1", "label": "Type"}, {"key": "c2", "label": "Length"}, {"key": "c3", "label": "Description"}]}]}, "comparison_hash": "7f6e968716966dae8869d6c14f0a6aa229d745d4d4bde899b61eeec58c8d7ea0", "manual_language": "zh", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a066.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a066.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

", "source_revalidation": {"kind": "static-same-version-source-and-manual-replay", "audit": "wiki-audit-20261023", "runtime_rerun": false, "compared_fields": "entity membership and source-derived facts; presentation markup normalized", "source_revision": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701", "previous_source_revision": "83157ee9c599d03b2f7a3d73ef3a56ec24e0e79cc2b3501a64d1364f56398c86"}}, "20": {"facts": [], "tables": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "related": [], "release": {"ref": "https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.bz2", "label": "20devel", "major": "20", "channel": "devel", "revision": 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"layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": 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\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 \uff09\u3002", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a066.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a066.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "summary": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 66.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 \uff09\u3002", "version": "20", "link_map": {"/zh/docs/devel/storage-toast.html": "/docs/devel/storage-toast.html", "/zh/docs/devel/storage-page-layout.html#STORAGE-TUPLE-LAYOUT": "/docs/devel/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "/zh/docs/devel/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE": "/docs/devel/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE"}, "body_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a066.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a066.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

", "body_sha256": "02e30c03a6786eb363ca834a8781cad85bdd854387940d3d0002c969cca8375e", "content_hash": "9983674e53951750ba916530af10cb870af4a9dee3bd5372bcc533ef23c04ba0", "source_database": "center", "source_revision": "49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac"}, "signature": "", "tables_zh": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "description": ["\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 66.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 \uff09\u3002"], "manual_html": "", "manual_path": "/docs/devel/storage-page-layout.html", "sections_zh": [], "localization": {"status": "complete", "sources": [{"url": "/docs/devel/storage-page-layout.html", "method": "same-major semantic node", "sha256": "e6342ac6dbc18d88c4c1a9a53b24c520b5ce2b76d9de4170ad8f151e1699e445", "language": "zh", "matched_nodes": ["#STORAGE-PAGE-LAYOUT/div[18]/div[2]/p[0]", "#STORAGE-PAGE-LAYOUT/div[18]/p[1]", "#STORAGE-PAGE-LAYOUT/div[18]/p[4]", "#STORAGE-PAGE-LAYOUT/div[18]/p[5]", "#STORAGE-PAGE-LAYOUT/div[18]/p[6]", "#STORAGE-PAGE-LAYOUT/div[1]"]}], "language": "zh", "original_text": {"/summary": "Physical row headers, null bitmap, alignment and column data.", "/category": "Physical structures", "/versions/20/description/0": "Physical row headers, null bitmap, alignment and column data.", "/versions/20/tables/0/title": "HeapTupleHeaderData Layout", "/versions/20/tables/0/rows/0/c2": "4 bytes", "/versions/20/tables/0/rows/0/c3": "insert XID stamp", "/versions/20/tables/0/rows/1/c2": "4 bytes", "/versions/20/tables/0/rows/1/c3": "delete XID stamp", "/versions/20/tables/0/rows/2/c2": "4 bytes", "/versions/20/tables/0/rows/2/c3": "insert and/or delete CID stamp (overlays with t_xvac)", "/versions/20/tables/0/rows/3/c2": "4 bytes", "/versions/20/tables/0/rows/3/c3": "XID for VACUUM operation moving a row version", "/versions/20/tables/0/rows/4/c2": "6 bytes", "/versions/20/tables/0/rows/4/c3": "current TID of this or newer row version", "/versions/20/tables/0/rows/5/c2": "2 bytes", "/versions/20/tables/0/rows/5/c3": "number of attributes, plus various flag bits", "/versions/20/tables/0/rows/6/c2": "2 bytes", "/versions/20/tables/0/rows/6/c3": "various flag bits", "/versions/20/tables/0/rows/7/c2": "1 byte", "/versions/20/tables/0/rows/7/c3": "offset to user data", "/versions/20/tables/0/columns/0/label": "Field", "/versions/20/tables/0/columns/1/label": "Type", "/versions/20/tables/0/columns/2/label": "Length", "/versions/20/tables/0/columns/3/label": "Description"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "ef036e64da1bc08b18151c8e2aba43834d424458c5e0595f3ad1315c6b05adc4", "canonical_center_text_hash": "9983674e53951750ba916530af10cb870af4a9dee3bd5372bcc533ef23c04ba0"}, "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 66.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 \uff09\u3002", "comparison_data": {"layouts": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 bytes", "c3": "insert XID stamp"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 bytes", "c3": "delete XID stamp"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 bytes", "c3": "insert and/or delete CID stamp (overlays with t_xvac)"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 bytes", "c3": "XID for VACUUM operation moving a row version"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 bytes", "c3": "current TID of this or newer row version"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 bytes", "c3": "number of attributes, plus various flag bits"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 bytes", "c3": "various flag bits"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 byte", "c3": "offset to user data"}], "title": "HeapTupleHeaderData Layout", "columns": [{"key": "c0", "label": "Field"}, {"key": "c1", "label": "Type"}, {"key": "c2", "label": "Length"}, {"key": "c3", "label": "Description"}]}]}, "comparison_hash": "7f6e968716966dae8869d6c14f0a6aa229d745d4d4bde899b61eeec58c8d7ea0", "manual_language": "zh", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a066.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a066.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

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\u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": 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\u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 ", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a066.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a066.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "summary": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 66.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 ", "version": "18", "link_map": {"/zh/docs/18/storage-toast.html": "/docs/18/storage-toast.html", "/zh/docs/18/storage-page-layout.html#STORAGE-TUPLE-LAYOUT": "/docs/18/storage-page-layout.html#STORAGE-TUPLE-LAYOUT", "/zh/docs/18/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE": "/docs/18/storage-page-layout.html#HEAPTUPLEHEADERDATA-TABLE"}, "body_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a066.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a066.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

", "body_sha256": "fdb78139bd42903e18148f28126309adb9482eea686da6434524eeab15b0be78", "content_hash": "1f70f56a410ed4477fede1cfed6593bf2950c4a15fe020c47ddb55a1f4f7f7f7", "source_database": "center", "source_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "signature": "", "tables_zh": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u4e8b\u52a1\u7684 XID"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "\u5220\u9664\u4e8b\u52a1\u7684 XID"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 \u5b57\u8282", "c3": "\u63d2\u5165\u548c\uff0f\u6216\u5220\u9664\u547d\u4ee4\u7684 CID\uff0c\u4e0e t_xvac \u5171\u7528\u5b58\u50a8\u4f4d\u7f6e"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 \u5b57\u8282", "c3": "VACUUM \u64cd\u4f5c\u79fb\u52a8\u884c\u7248\u672c\u65f6\u4f7f\u7528\u7684 XID"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 \u5b57\u8282", "c3": "\u672c\u884c\u7248\u672c\u6216\u8f83\u65b0\u884c\u7248\u672c\u7684\u5f53\u524d TID"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5c5e\u6027\u6570\u91cf\u53ca\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 \u5b57\u8282", "c3": "\u5404\u79cd\u6807\u5fd7\u4f4d"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 \u5b57\u8282", "c3": "\u7528\u6237\u6570\u636e\u7684\u504f\u79fb\u91cf"}], "title": "HeapTupleHeaderData \u5e03\u5c40", "columns": [{"key": "c0", "label": "\u5b57\u6bb5"}, {"key": "c1", "label": "\u7c7b\u578b"}, {"key": "c2", "label": "\u957f\u5ea6"}, {"key": "c3", "label": "\u8bf4\u660e"}]}], "description": ["\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 66.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 "], "manual_html": "", "manual_path": "/docs/18/storage-page-layout.html", "sections_zh": [], "localization": {"status": "complete", "sources": [{"url": "/docs/18/storage-page-layout.html", "method": "same-major semantic node", "sha256": "e504ff90f2cabf6f71046d80f1cc8d49664ba2f2f4bce0ef26e955d6c5580ab2", "language": "zh", "matched_nodes": ["#STORAGE-PAGE-LAYOUT/div[18]/div[2]/p[0]", "#STORAGE-PAGE-LAYOUT/div[18]/p[1]", "#STORAGE-PAGE-LAYOUT/div[18]/p[4]", "#STORAGE-PAGE-LAYOUT/div[18]/p[5]", "#STORAGE-PAGE-LAYOUT/div[18]/p[6]", "#STORAGE-PAGE-LAYOUT/div[1]"]}], "language": "zh", "original_text": {"/versions/18/description/0": "Physical row headers, null bitmap, alignment and column data.", "/versions/18/tables/0/title": "HeapTupleHeaderData Layout", "/versions/18/tables/0/rows/0/c2": "4 bytes", "/versions/18/tables/0/rows/0/c3": "insert XID stamp", "/versions/18/tables/0/rows/1/c2": "4 bytes", "/versions/18/tables/0/rows/1/c3": "delete XID stamp", "/versions/18/tables/0/rows/2/c2": "4 bytes", "/versions/18/tables/0/rows/2/c3": "insert and/or delete CID stamp (overlays with t_xvac)", "/versions/18/tables/0/rows/3/c2": "4 bytes", "/versions/18/tables/0/rows/3/c3": "XID for VACUUM operation moving a row version", "/versions/18/tables/0/rows/4/c2": "6 bytes", "/versions/18/tables/0/rows/4/c3": "current TID of this or newer row version", "/versions/18/tables/0/rows/5/c2": "2 bytes", "/versions/18/tables/0/rows/5/c3": "number of attributes, plus various flag bits", "/versions/18/tables/0/rows/6/c2": "2 bytes", "/versions/18/tables/0/rows/6/c3": "various flag bits", "/versions/18/tables/0/rows/7/c2": "1 byte", "/versions/18/tables/0/rows/7/c3": "offset to user data", "/versions/18/tables/0/columns/0/label": "Field", "/versions/18/tables/0/columns/1/label": "Type", "/versions/18/tables/0/columns/2/label": "Length", "/versions/18/tables/0/columns/3/label": "Description"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "f0a44bd96ec79f5387e9c512ba7a6444f819cd1a32e4c0cdf82f78d6c9d7d5b2", "canonical_center_text_hash": "1f70f56a410ed4477fede1cfed6593bf2950c4a15fe020c47ddb55a1f4f7f7f7"}, "description_zh": "\u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1 \u8868 66.4 \u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0 MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728 t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09 \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728 src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002 \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea pg_attribute \u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f attlen \u548c attalign \u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr \u3001 fastgetattr \u548c heap_getsysattr \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002 \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena \uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1 \u7b2c 66.2 \u8282 ", "comparison_data": {"layouts": [{"key": "layout-2", "rows": [{"c0": "t_xmin", "c1": "TransactionId", "c2": "4 bytes", "c3": "insert XID stamp"}, {"c0": "t_xmax", "c1": "TransactionId", "c2": "4 bytes", "c3": "delete XID stamp"}, {"c0": "t_cid", "c1": "CommandId", "c2": "4 bytes", "c3": "insert and/or delete CID stamp (overlays with t_xvac)"}, {"c0": "t_xvac", "c1": "TransactionId", "c2": "4 bytes", "c3": "XID for VACUUM operation moving a row version"}, {"c0": "t_ctid", "c1": "ItemPointerData", "c2": "6 bytes", "c3": "current TID of this or newer row version"}, {"c0": "t_infomask2", "c1": "uint16", "c2": "2 bytes", "c3": "number of attributes, plus various flag bits"}, {"c0": "t_infomask", "c1": "uint16", "c2": "2 bytes", "c3": "various flag bits"}, {"c0": "t_hoff", "c1": "uint8", "c2": "1 byte", "c3": "offset to user data"}], "title": "HeapTupleHeaderData Layout", "columns": [{"key": "c0", "label": "Field"}, {"key": "c1", "label": "Type"}, {"key": "c2", "label": "Length"}, {"key": "c3", "label": "Description"}]}]}, "comparison_hash": "7f6e968716966dae8869d6c14f0a6aa229d745d4d4bde899b61eeec58c8d7ea0", "manual_language": "zh", "description_zh_html": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a066.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a066.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

", "center_zh_rendered": "

\u5b58\u50a8\u7ed3\u6784 tuple-layout\u3002

\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009

\n\n \u6240\u6709\u8868\u884c\u7684\u7ed3\u6784\u90fd\u76f8\u540c\u3002\u5b83\u4eec\u90fd\u6709\u4e00\u4e2a\u56fa\u5b9a\u5927\u5c0f\u7684\u5934\u90e8\uff08\u5728\u5927\u591a\u6570\u673a\u5668\u4e0a\u5360 23 \u5b57\u8282\uff09\uff0c\u540e\u9762\u8ddf\u7740\u53ef\u9009\u7684\u7a7a\u503c\u4f4d\u56fe\u3001\u53ef\u9009\u7684\u5bf9\u8c61 ID \u5b57\u6bb5\u4ee5\u53ca\u7528\u6237\u6570\u636e\u3002\u5934\u90e8\u7684\u8be6\u7ec6\u683c\u5f0f\u89c1\u8868\u00a066.4\u3002\u5b9e\u9645\u7528\u6237\u6570\u636e\uff08\u884c\u7684\u5404\u5217\uff09\u4ece\n t_hoff \u6307\u793a\u7684\u504f\u79fb\u4f4d\u7f6e\u5f00\u59cb\uff0c\u5b83\u5fc5\u987b\u59cb\u7ec8\u662f\u8be5\u5e73\u53f0\n MAXALIGN \u5bf9\u9f50\u5355\u4f4d\u7684\u6574\u6570\u500d\u3002\u53ea\u6709\u5f53 HEAP_HASNULL \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u7a7a\u503c\u4f4d\u56fe\u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u7d27\u968f\u56fa\u5b9a\u5934\u90e8\u4e4b\u540e\uff0c\u5e76\u5360\u7528\u8db3\u591f\u591a\u7684\u5b57\u8282\uff0c\u4ee5\u4fbf\u4e3a\u6bcf\u4e2a\u6570\u636e\u5217\u63d0\u4f9b\u4e00\u4f4d\uff08\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4f4d\u6570\u7b49\u4e8e t_infomask2 \u4e2d\u7684\u5c5e\u6027\u4e2a\u6570\uff09\u3002\u5728\u8fd9\u4e2a\u4f4d\u56fe\u4e2d\uff0c1 \u8868\u793a\u975e\u7a7a\uff0c0 \u8868\u793a\u7a7a\u503c\u3002\u5f53\u4f4d\u56fe\u4e0d\u5b58\u5728\u65f6\uff0c\u5047\u5b9a\u6240\u6709\u5217\u90fd\u975e\u7a7a\u3002\u53ea\u6709\u5f53 HEAP_HASOID_OLD \u4f4d\u5728\n t_infomask \u4e2d\u88ab\u7f6e\u4f4d\u65f6\uff0c\u5bf9\u8c61 ID \u624d\u5b58\u5728\u3002\u82e5\u5b58\u5728\uff0c\u5b83\u4f4d\u4e8e\n t_hoff \u8fb9\u754c\u4e4b\u524d\u3002\u4e3a\u4e86\u8ba9 t_hoff\n \u6210\u4e3a MAXALIGN \u7684\u6574\u6570\u500d\u6240\u9700\u7684\u4efb\u4f55\u586b\u5145\uff0c\u90fd\u4f1a\u51fa\u73b0\u5728\u7a7a\u503c\u4f4d\u56fe\u4e0e\u5bf9\u8c61 ID \u4e4b\u95f4\u3002\uff08\u8fd9\u53c8\u53cd\u8fc7\u6765\u4fdd\u8bc1\u4e86\u5bf9\u8c61 ID \u7684\u5bf9\u9f50\u662f\u5408\u9002\u7684\u3002\uff09\n\n

\n \u6240\u6709\u7ec6\u8282\u90fd\u53ef\u4ee5\u5728\n src/include/access/htup_details.h \u4e2d\u627e\u5230\u3002\n

\n\n \u8981\u89e3\u91ca\u5b9e\u9645\u6570\u636e\uff0c\u5fc5\u987b\u501f\u52a9\u4ece\u5176\u4ed6\u8868\u4e2d\u83b7\u5f97\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u6765\u81ea\n pg_attribute\u3002\u8bc6\u522b\u5b57\u6bb5\u4f4d\u7f6e\u6240\u9700\u7684\u5173\u952e\u503c\u662f\n attlen \u548c attalign\u3002\u9664\u975e\u6240\u6709\u5b57\u6bb5\u90fd\u662f\u5b9a\u5bbd\u4e14\u6ca1\u6709\u7a7a\u503c\uff0c\u5426\u5219\u6ca1\u6709\u529e\u6cd5\u76f4\u63a5\u53d6\u5f97\u67d0\u4e2a\u7279\u5b9a\u5c5e\u6027\u3002\u6240\u6709\u8fd9\u4e9b\u6280\u5de7\u90fd\u5c01\u88c5\u5728 heap_getattr\u3001fastgetattr \u548c heap_getsysattr\n \u8fd9\u4e9b\u51fd\u6570\u4e2d\u3002\n\n

\n\n \u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u9700\u8981\u4f9d\u6b21\u68c0\u67e5\u6bcf\u4e2a\u5c5e\u6027\u3002\u9996\u5148\u6839\u636e\u7a7a\u503c\u4f4d\u56fe\u5224\u65ad\u8be5\u5b57\u6bb5\u662f\u5426\u4e3a NULL\u3002\u5982\u679c\u662f\uff0c\u5c31\u7ee7\u7eed\u4e0b\u4e00\u4e2a\u3002\u7136\u540e\u786e\u8ba4\u5bf9\u9f50\u662f\u5426\u6b63\u786e\u3002\u5982\u679c\u5b57\u6bb5\u662f\u5b9a\u5bbd\u5b57\u6bb5\uff0c\u90a3\u4e48\u5b83\u7684\u6240\u6709\u5b57\u8282\u90fd\u662f\u76f4\u63a5\u6446\u653e\u7684\uff1b\u5982\u679c\u5b83\u662f\u53d8\u957f\u5b57\u6bb5\uff08attlen = -1\uff09\uff0c\u60c5\u51b5\u5c31\u4f1a\u7a0d\u590d\u6742\u4e00\u4e9b\u3002\u6240\u6709\u53d8\u957f\u6570\u636e\u7c7b\u578b\u90fd\u5171\u4eab\u4e00\u4e2a\u901a\u7528\u5934\u90e8\u7ed3\u6784\u4f53 struct varlena\uff0c\u5176\u4e2d\u5305\u542b\u5df2\u5b58\u50a8\u503c\u7684\u603b\u957f\u5ea6\u4ee5\u53ca\u4e00\u4e9b\u6807\u5fd7\u4f4d\u3002\u6839\u636e\u8fd9\u4e9b\u6807\u5fd7\uff0c\u6570\u636e\u53ef\u80fd\u662f\u884c\u5185\u5b58\u50a8\u7684\uff0c\u4e5f\u53ef\u80fd\u4f4d\u4e8e\n TOAST \u8868\u4e2d\uff1b\u5b83\u4e5f\u53ef\u80fd\u662f\u7ecf\u8fc7\u538b\u7f29\u7684\uff08\u89c1\u7b2c\u00a066.2\u00a0\u8282\uff09\u3002\n\n

\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587\u3002

"}, "comparison": {"left": "10", "right": "11", "status": "added", "diff": "--- PostgreSQL 10\n+++ PostgreSQL 11\n@@ -1 +1,76 @@\n-\u8be5\u7248\u672a\u6536\u5f55\n+{\n+ \"layouts\": [\n+ {\n+ \"columns\": [\n+ {\n+ \"key\": \"c0\",\n+ \"label\": \"Field\"\n+ },\n+ {\n+ \"key\": \"c1\",\n+ \"label\": \"Type\"\n+ },\n+ {\n+ \"key\": \"c2\",\n+ \"label\": \"Length\"\n+ },\n+ {\n+ \"key\": \"c3\",\n+ \"label\": \"Description\"\n+ }\n+ ],\n+ \"key\": \"layout-2\",\n+ \"rows\": [\n+ {\n+ \"c0\": \"t_xmin\",\n+ \"c1\": \"TransactionId\",\n+ \"c2\": \"4 bytes\",\n+ \"c3\": \"insert XID stamp\"\n+ },\n+ {\n+ \"c0\": \"t_xmax\",\n+ \"c1\": \"TransactionId\",\n+ \"c2\": \"4 bytes\",\n+ \"c3\": \"delete XID stamp\"\n+ },\n+ {\n+ \"c0\": \"t_cid\",\n+ \"c1\": \"CommandId\",\n+ \"c2\": \"4 bytes\",\n+ \"c3\": \"insert and/or delete CID stamp (overlays with t_xvac)\"\n+ },\n+ {\n+ \"c0\": \"t_xvac\",\n+ \"c1\": \"TransactionId\",\n+ \"c2\": \"4 bytes\",\n+ \"c3\": \"XID for VACUUM operation moving a row version\"\n+ },\n+ {\n+ \"c0\": \"t_ctid\",\n+ \"c1\": \"ItemPointerData\",\n+ \"c2\": \"6 bytes\",\n+ \"c3\": \"current TID of this or newer row version\"\n+ },\n+ {\n+ \"c0\": \"t_infomask2\",\n+ \"c1\": \"uint16\",\n+ \"c2\": \"2 bytes\",\n+ \"c3\": \"number of attributes, plus various flag bits\"\n+ },\n+ {\n+ \"c0\": \"t_infomask\",\n+ \"c1\": \"uint16\",\n+ \"c2\": \"2 bytes\",\n+ \"c3\": \"various flag bits\"\n+ },\n+ {\n+ \"c0\": \"t_hoff\",\n+ \"c1\": \"uint8\",\n+ \"c2\": \"1 byte\",\n+ \"c3\": \"offset to user data\"\n+ }\n+ ],\n+ \"title\": \"HeapTupleHeaderData Layout\"\n+ }\n+ ]\n+}"}}