在 PostgreSQL 中查找死锁

在 PostgreSQL 中查找死锁可以使用如下查询语句：

SELECT blocked_locks.pid AS blocked_pid,
       blocking_locks.pid AS blocking_pid,
       blocked_activity.query AS blocked_query,
       blocking_activity.query AS blocking_query
FROM pg_catalog.pg_locks blocked_locks
JOIN pg_catalog.pg_stat_activity blocked_activity ON blocked_activity.pid = blocked_locks.pid
JOIN pg_catalog.pg_locks blocking_locks ON (blocking_locks.locktype = blocked_locks.locktype AND
                                             blocking_locks.DATABASE IS NOT DISTINCT FROM blocked_locks.DATABASE AND
                                             blocking_locks.relation IS NOT DISTINCT FROM blocked_locks.relation AND 
                                             blocking_locks.page IS NOT DISTINCT FROM blocked_locks.page AND
                                             blocking_locks.tuple IS NOT DISTINCT FROM blocked_locks.tuple AND
                                             blocking_locks.virtualxid IS NOT DISTINCT FROM blocked_locks.virtualxid AND
                                             blocking_locks.transactionid IS NOT DISTINCT FROM blocked_locks.transactionid AND
                                             blocking_locks.classid IS NOT DISTINCT FROM blocked_locks.classid AND
                                             blocking_locks.objid IS NOT DISTINCT FROM blocked_locks.objid AND
                                             blocking_locks.objsubid IS NOT DISTINCT FROM blocked_locks.objsubid AND
                                             blocking_locks.pid != blocked_locks.pid)
JOIN pg_catalog.pg_stat_activity blocking_activity ON blocking_activity.pid = blocking_locks.pid
WHERE blocked_locks.granted AND NOT blocking_locks.granted;

这个查询将会返回当前所有的死锁情况，其中包括阻塞进程与被阻塞进程的 PID 和 SQL 语句。通过对查询结果进行分析可以确定死锁产生的原因， 进而选择相应的方式解除死锁。