PostgreSQL查看是否锁表的方法本步骤


    目录
  • 查看当前所有锁
  • 查看特定表的锁
  • 查看数据库级别的锁
  • 查看事务锁的阻塞情况
  • 解释
  • 查看锁的等待时间
  • 注意事项

    查看当前所有锁
    查询 pg_locks 系统视图可以查看当前数据库中的所有锁信息：
    
SELECT
    locktype,
    database AS db_oid,
    relation AS rel_oid,
    page,
    tuple,
    virtualtransaction,
    pid,
    mode,
    granted
FROM pg_locks;

    
  • locktype：锁的类型，如表锁、行锁等。
  • relation：被锁定的表的 OID，可以通过 pg_class 视图查询表名。
  • pid：持有锁的进程 ID。
  • mode：锁的模式，如 AccessShareLock、RowExclusiveLock 等。
  • granted：是否已经获得锁。

    查看特定表的锁
    如果你想查看特定表的锁信息，可以结合 pg_class 视图来过滤：
    
SELECT
    l.locktype,
    l.database AS db_oid,
    l.relation AS rel_oid,
    l.page,
    l.tuple,
    l.virtualtransaction,
    l.pid,
    l.mode,
    l.granted,
    c.relname AS table_name
FROM pg_locks l
JOIN pg_class c ON l.relation = c.oid
WHERE c.relname = 'your_table_name'; -- 替换为你的表名

    查看数据库级别的锁
    如果你怀疑数据库级别的锁，可以使用以下查询：
    
SELECT
    l.locktype,
    l.database AS db_oid,
    l.relation AS rel_oid,
    l.page,
    l.tuple,
    l.virtualtransaction,
    l.pid,
    l.mode,
    l.granted,
    d.datname AS database_name
FROM pg_locks l
JOIN pg_database d ON l.database = d.oid;

    查看事务锁的阻塞情况
    为了查看事务锁的阻塞情况，可以使用以下查询：
    
SELECT
    blocked_pid,
    blocking_pid,
    blocked_activity.query AS blocked_query,
    blocking_activity.query AS blocking_query,
    blocked_activity.pid AS blocked_pid,
    blocking_activity.pid AS blocking_pid
FROM
    (
        SELECT
            pid AS blocked_pid,
            pg_locks.locked_row.mode AS lock_mode,
            pg_locks.locked_row.relation AS relation,
            pg_locks.blocking_pid AS blocking_pid
        FROM
            pg_locks AS locked_row
            JOIN pg_locks AS blocking_lock ON
                locked_row.locktype = blocking_lock.locktype AND
                locked_row.database = blocking_lock.database AND
                locked_row.relation = blocking_lock.relation AND
                locked_row.page = blocking_lock.page AND
                locked_row.tuple = blocking_lock.tuple AND
                locked_row.virtualxid = blocking_lock.virtualxid AND
                locked_row.transactionid = blocking_lock.transactionid AND
                locked_row.classid = blocking_lock.classid AND
                locked_row.objid = blocking_lock.objid AND
                locked_row.objsubid = blocking_lock.objsubid AND
                locked_row.pid != blocking_lock.pid AND
                NOT locked_row.granted AND
                blocking_lock.granted
    ) AS blocked_locks
JOIN pg_stat_activity AS blocked_activity ON blocked_locks.blocked_pid = blocked_activity.pid
JOIN pg_stat_activity AS blocking_activity ON blocked_locks.blocking_pid = blocking_activity.pid;

    解释
  • blocked_pid：被阻塞的进程 ID。
  • blocking_pid：阻塞其他进程的进程 ID。
  • blocked_query：被阻塞的查询。
  • blocking_query：阻塞其他查询的查询。

    查看锁的等待时间
    如果你想知道锁的等待时间，可以结合 pg_stat_activity 视图：
    
SELECT
    pid,
    query,
    state,
    wait_event_type,
    wait_event,
    now() - query_start AS waiting_time
FROM pg_stat_activity
WHERE state = 'active' AND wait_event_type IS NOT NULL;

    注意事项
  • 锁是数据库操作的正常部分，但长时间的锁可能会影响性能。
  • 如果发现锁竞争严重，可以考虑优化查询、索引或事务逻辑。
  • 频繁的锁问题可能需要调整数据库的隔离级别或锁策略。

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