跳转到主要内容

BufferPin: BufferPin

等待获取 buffer 上的独占 pin。
PostgreSQL 等待事件档案
类别BufferPin 事件BufferPin 版本PG 13-18 证据2 个源码位置

官方描述译文

等待获取 buffer 上的独占 pin。

PG 13 PG 14 PG 15 PG 16 PG 17 PG 18

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。

正常还是麻烦?

  • 正常: 扫描或索引维护期间,孤立的亚秒级样本可能正常。
  • 需要调查: 等待超过一秒就值得怀疑,尤其要检查游标或空闲事务是否持续钉住页面。

诊断 SQL

正在等待 BufferPin/BufferPin 的会话
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;
当前 BufferPin 等待分布
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;
这些会话的锁与关系上下文
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;

处置建议

  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。

源码证据