heap

说明

本章说明 PostgreSQL 核心系统与管理表存储的 表访问方法 之间的接口。除这里规定的内容之外，核心系统对这些访问方法知之甚少，因此可以通过编写附加代码来开发全新的访问方法类型。 每个表访问方法都由系统目录 pg_am 中的一行描述。 pg_am 条目指定了该表访问方法的名称以及一个 处理器函数 。这些条目可以通过 CREATE ACCESS METHOD 和 DROP ACCESS METHOD SQL 命令创建和删除。 表访问方法的处理器函数必须声明为接受一个 internal 类型的参数，并返回伪类型 table_am_handler 。这个参数只是一个占位值，用来防止处理器函数被 SQL 命令直接调用。 下面展示扩展 SQL 脚本文件如何创建表访问方法处理器：

接口类别

表访问方法

处理函数或例程

heapam_methods

记录的回调

43

接口与能力边界

矩阵记录此源码构建实际注册的回调。注册表明实现了相应接口钩子；操作是否允许还取决于选项、查询形式、权限和提供方规则。

下方保留同版本完整手册，包括配置、约束和示例。不声称已进行运行时能力测试。

堆存储、可见性与 WAL

此清单从 PostgreSQL 12 引入的 Table AM 接口开始。不会将更早版本的 PostgreSQL 堆存储重新标为 Table AM 实现。

堆可见性遵循 PostgreSQL 快照。WAL 和崩溃恢复行为取决于关系的持久性；临时表、无日志表与永久表不同。索引访问方法与表存储接口分开。

核心源码中注册的实现

{
	.type = T_TableAmRoutine,

	.slot_callbacks = heapam_slot_callbacks,

	.scan_begin = heap_beginscan,
	.scan_end = heap_endscan,
	.scan_rescan = heap_rescan,
	.scan_getnextslot = heap_getnextslot,

	.scan_set_tidrange = heap_set_tidrange,
	.scan_getnextslot_tidrange = heap_getnextslot_tidrange,

	.parallelscan_estimate = table_block_parallelscan_estimate,
	.parallelscan_initialize = table_block_parallelscan_initialize,
	.parallelscan_reinitialize = table_block_parallelscan_reinitialize,

	.index_fetch_begin = heapam_index_fetch_begin,
	.index_fetch_reset = heapam_index_fetch_reset,
	.index_fetch_end = heapam_index_fetch_end,
	.index_fetch_tuple = heapam_index_fetch_tuple,

	.tuple_insert = heapam_tuple_insert,
	.tuple_insert_speculative = heapam_tuple_insert_speculative,
	.tuple_complete_speculative = heapam_tuple_complete_speculative,
	.multi_insert = heap_multi_insert,
	.tuple_delete = heapam_tuple_delete,
	.tuple_update = heapam_tuple_update,
	.tuple_lock = heapam_tuple_lock,

	.tuple_fetch_row_version = heapam_fetch_row_version,
	.tuple_get_latest_tid = heap_get_latest_tid,
	.tuple_tid_valid = heapam_tuple_tid_valid,
	.tuple_satisfies_snapshot = heapam_tuple_satisfies_snapshot,
	.index_delete_tuples = heap_index_delete_tuples,

	.relation_set_new_filelocator = heapam_relation_set_new_filelocator,
	.relation_nontransactional_truncate = heapam_relation_nontransactional_truncate,
	.relation_copy_data = heapam_relation_copy_data,
	.relation_copy_for_cluster = heapam_relation_copy_for_cluster,
	.relation_vacuum = heap_vacuum_rel,
	.scan_analyze_next_block = heapam_scan_analyze_next_block,
	.scan_analyze_next_tuple = heapam_scan_analyze_next_tuple,
	.index_build_range_scan = heapam_index_build_range_scan,
	.index_validate_scan = heapam_index_validate_scan,

	.relation_size = table_block_relation_size,
	.relation_needs_toast_table = heapam_relation_needs_toast_table,
	.relation_toast_am = heapam_relation_toast_am,
	.relation_fetch_toast_slice = heap_fetch_toast_slice,

	.relation_estimate_size = heapam_estimate_rel_size,

	.scan_bitmap_next_tuple = heapam_scan_bitmap_next_tuple,
	.scan_sample_next_block = heapam_scan_sample_next_block,
	.scan_sample_next_tuple = heapam_scan_sample_next_tuple
}

相关条目

• 系统目录 pg_am
• default_table_access_method
• 索引访问方法

文档与源码

• PostgreSQL 18 English manual
• src/backend/access/heap/heapam_handler.c:2616
• PostgreSQL 18 English manual
• PostgreSQL 18 English manual
• PostgreSQL 18 English manual
• PostgreSQL 18 English manual

版本比较

PostgreSQL 13 → 14: 属性变化。

以下差异保留原始字段名与英文源描述。

--- PostgreSQL 13
+++ PostgreSQL 14
@@ -1,7 +1,7 @@
 {
   "callbacks": {
-    "compute_xid_horizon_for_tuples": "heap_compute_xid_horizon_for_tuples",
     "index_build_range_scan": "heapam_index_build_range_scan",
+    "index_delete_tuples": "heap_index_delete_tuples",
     "index_fetch_begin": "heapam_index_fetch_begin",
     "index_fetch_end": "heapam_index_fetch_end",
     "index_fetch_reset": "heapam_index_fetch_reset",
@@ -28,9 +28,11 @@
     "scan_bitmap_next_tuple": "heapam_scan_bitmap_next_tuple",
     "scan_end": "heap_endscan",
     "scan_getnextslot": "heap_getnextslot",
+    "scan_getnextslot_tidrange": "heap_getnextslot_tidrange",
     "scan_rescan": "heap_rescan",
     "scan_sample_next_block": "heapam_scan_sample_next_block",
     "scan_sample_next_tuple": "heapam_scan_sample_next_tuple",
+    "scan_set_tidrange": "heap_set_tidrange",
     "slot_callbacks": "heapam_slot_callbacks",
     "tuple_complete_speculative": "heapam_tuple_complete_speculative",
     "tuple_delete": "heapam_tuple_delete",

比较已记录的接口与属性，排除来源指纹和构建元数据。某个样本中没有记录，不能据此判断实际引入或移除的版本。