Buffer/BufferPin

各版本描述

相邻版本里类型、名称与英文描述都相同的合并成一段，旧的在前。中文取自图谱或本站手册译文，没有译文的只给英文原文。

1. 9.6–12

   BufferPin/BufferPin曾用名

   等待获取缓冲区上的钉住。

   Waiting to acquire a pin on a buffer.

2. 13–18

   BufferPin/BufferPin曾用名

   等待获得缓冲区上的独占销。

   Waiting to acquire an exclusive pin on a buffer

触发机制

WAIT_EVENT_BUFFER_PIN 位于 src/backend/storage/buffer/bufmgr.c:5819，是经 grep 核验的报告路径。公共身份/资源映射位于 src/backend/utils/activity/wait_event_names.txt:286。探针覆盖的操作是：等待获取 buffer 上的独占 pin。缓冲区管理器需要独占 pin，但另一个后端仍在同一共享缓冲区上持有 pin；当前后端会休眠到最后一个冲突 pin 被释放。

WAIT_EVENT_BUFFER_PIN at src/backend/storage/buffer/bufmgr.c:5819 is the grep-verified reporting path. The public identity/resource is mapped at src/backend/utils/activity/wait_event_names.txt:286. The instrumented operation is: Waiting to acquire an exclusive pin on a buffer. The buffer manager needs an exclusive pin, but another backend still holds a pin on the same shared buffer. It sleeps until the last conflicting pin is released.

诊断 SQL

直接在 psql 里跑；标注的是语句里用到的视图与列所要求的最低版本。

SELECT pid, backend_type, usename, datname, application_name,
       state, now() - query_start AS query_age,
       now() - xact_start AS xact_age,
       wait_event_type, wait_event,
       pg_blocking_pids(pid) AS blocking_pids,
       left(query, 160) AS query
FROM pg_stat_activity
WHERE wait_event_type = 'BufferPin'
  AND wait_event = 'BufferPin'
ORDER BY query_age DESC NULLS LAST;

SELECT wait_event, count(*) AS waiting_sessions,
       count(*) FILTER (WHERE state = 'active') AS active_waiters,
       max(now() - query_start) AS oldest_query
FROM pg_stat_activity
WHERE wait_event_type = 'BufferPin'
GROUP BY wait_event
ORDER BY waiting_sessions DESC, wait_event;

SELECT a.pid, l.locktype, l.mode, l.granted, l.fastpath,
       d.datname, n.nspname, c.relname,
       l.page, l.tuple, l.virtualxid, l.transactionid,
       l.classid, l.objid, l.objsubid
FROM pg_stat_activity AS a
LEFT JOIN pg_locks AS l ON l.pid = a.pid
LEFT JOIN pg_database AS d ON d.oid = l.database
LEFT JOIN pg_class AS c
  ON c.oid = l.relation
 AND l.database = (
       SELECT oid FROM pg_database WHERE datname = current_database()
     )
LEFT JOIN pg_namespace AS n ON n.oid = c.relnamespace
WHERE a.wait_event_type = 'BufferPin'
  AND a.wait_event = 'BufferPin'
ORDER BY a.pid, l.granted, l.locktype, l.mode;

处置步骤

1. 保全等待查询与关系上下文。
2. 查找访问同一关系的长游标与 idle in transaction 会话。
3. 确认最安全的持有者或维护受害者后再取消。

相关参数与指标

waiting_sessionswait_event_share

源码证据

图谱在各版本源码树里核对到的位置，新的在前。「触发点」是真正上报等待事件的调用处，「目录定义」只说明这个名字在枚举里存在。

演化历史

相邻两个大版本之间的差异，新的在前。版本号链到该版的变动清单。

1. PostgreSQL 19 ← 18 移除此事件

   该版起不再存在

2. PostgreSQL 13 ← 12 描述更新

   描述措辞更新

   等待获得缓冲区上的独占销。

   描述前后对照

   Waiting to acquire a pin on a buffer. Waiting to acquire an exclusive pin on a buffer.

3. PostgreSQL 9.6 新增此事件

   9.6 引入等待事件机制，此为本事件的首个版本

   等待获取缓冲区上的钉住。

同类事件