LWLock/LockManager

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

   LWLockTranche/lock_manager曾用名

   等待添加或检查后端的锁，或者等待加入或退出锁组（用于并行查询）。

   Waiting to add or examine locks for backends, or waiting to join or exit a locking group (used by parallel query).

2. 10–12

   LWLock/lock_manager曾用名

   等待添加或检查后端的锁，或者等待加入或退出锁组（用于并行查询）。

   Waiting to add or examine locks for backends, or waiting to join or exit a locking group (used by parallel query).

3. 13–16

   LWLock/LockManager

   等待读取或更新有关“重量级”锁的信息。

   Waiting to read or update information about “heavyweight” locks.

4. 17–18

   LWLock/LockManager

   等待读取或更新有关“重量级”锁的信息。

   Waiting to read or update information about "heavyweight" locks

5. 19–20

   LWLock/LockManager

   等待读取或更新有关“重量级”锁的信息。

   Waiting to read or update information about “heavyweight” locks.

触发机制

重量级锁的账本存放在由 LockHashPartitionLock 分区保护的共享哈希表中。获取、授予、释放或检查大量重量级锁时，即使不存在 SQL 层锁冲突，也可能在分区锁上竞争。

Heavyweight lock bookkeeping is stored in shared hash tables partitioned by LockHashPartitionLock. Acquiring, granting, releasing, or inspecting many heavyweight locks can contend on the partition even when no SQL-level lock conflict exists.

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 = 'LWLock'
  AND wait_event = 'LockManager'
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 = 'LWLock'
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 = 'LWLock'
  AND a.wait_event = 'LockManager'
ORDER BY a.pid, l.granted, l.locktype, l.mode;

处置步骤

1. 按 PID 统计 pg_locks 行数并检查阻塞树。
2. 定位一次触碰大量关系或分区的语句。
3. 缩短事务并降低锁扇出；只有真实容量报错时才提高 max_locks_per_transaction。

相关参数与指标

max_locks_per_transactionmax_connections waiting_sessionswait_event_sharelocks_per_backendblocked_sessions

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 描述更新

   描述措辞更新

   等待读取或更新有关“重量级”锁的信息。

   描述前后对照

   Waiting to read or update information about "heavyweight" locks Waiting to read or update information about “heavyweight” locks.

2. PostgreSQL 17 ← 16 描述更新

   描述措辞更新

   等待读取或更新有关“重量级”锁的信息。

   描述前后对照

   Waiting to read or update information about “heavyweight” locks. Waiting to read or update information about "heavyweight" locks

3. PostgreSQL 13 ← 12 更名

   更名 lock_manager→LockManager 描述措辞更新

   等待读取或更新有关“重量级”锁的信息。

   描述前后对照

   Waiting to add or examine locks for backends, or waiting to join or exit a locking group (used by parallel query). Waiting to read or update information about “heavyweight” locks.

4. PostgreSQL 10 ← 9.6 类型变动

   类型 LWLockTranche→LWLock

   等待添加或检查后端的锁，或者等待加入或退出锁组（用于并行查询）。

5. 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

   等待添加或检查后端的锁，或者等待加入或退出锁组（用于并行查询）。

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