postgresql表死锁问题的排查方式

1.查询激活的执行中的sql,查看有哪些更新update的sql。

									select *

									from pg_stat_activity

									where state = 'active';

2. 查询表中存在的锁

									select a.locktype, a.database, a.pid, a.mode, a.relation, b.relname

									from pg_locks a

									join pg_class b on a.relation = b.oid

									where lower(b.relname) = 'h5_game';

3. 杀掉死锁进程

									select pg_terminate_backend(pid)

									from pg_stat_activity

									where state = 'active'

									and pid != pg_backend_pid()

									--and pid = 14172

									and pid in (select a.pid

									from pg_locks a

									join pg_class b on a.relation = b.oid

									where lower(b.relname) = 'news_content')

锁模式

									/* NoLock is not a lock mode, but a flag value meaning "don't get a lock" */

									#define NoLock                 0

									#define AccessShareLock         1        /* SELECT */

									#define RowShareLock          2        /* SELECT FOR UPDATE/FOR SHARE */

									#define RowExclusiveLock        3        /* INSERT, UPDATE, DELETE */

									#define ShareUpdateExclusiveLock 4       /* VACUUM (non-FULL),ANALYZE, CREATE

									                                         * INDEX CONCURRENTLY */

									#define ShareLock                5        /* CREATE INDEX (WITHOUT CONCURRENTLY) */

									#define ShareRowExclusiveLock  6        /* like EXCLUSIVE MODE, but allows ROW

									                                         * SHARE */

									#define ExclusiveLock          7        /* blocks ROW SHARE/SELECT...FOR

									                                         * UPDATE */

									#define AccessExclusiveLock       8        /* ALTER TABLE, DROP TABLE, VACUUM

									                                         * FULL, and unqualified LOCK TABLE */

补充：Postgresql死锁的处理

背景：

对表进行所有操作都卡住，原因可能是更新表时导致这个表死锁了，开始进行排查

解决一：查询pg_stat_activity有没有记录

pg版本10.2

									select pid,query,* from pg_stat_activity where datname='死锁的数据库' and wait_event_type = 'Lock';

									select pg_cancel_backend('死锁那条数据的pid值');##只能杀死select 语句, 对其他语句不生效

									pg_terminate_backend('死锁那条数据的pid值');#select,drop等各种操作

执行后发现select和delete表时正常执行，但truncate和drop表时会一直运行，也不报错。

“drop table” 和 “truncate table” 需要申请排它锁"ACCESS EXCLUSIVE"，执行这个命令卡住时，说明此时这张表上还有操作正在进行，比如查询等，

那么只有等待这个查询操作完成，“drop table” 或"truncate table"或者增加字段的SQL才能获取这张表上的 "ACCESS EXCLUSIVE"锁，操作才能进行下去。

解决二：查询pg_locks是否有这个对象的锁

									select oid,relname from pg_class where relname='table name';

									select locktype,pid,relation,mode,granted,* from pg_locks where relation= '上面查询出来的oid';

									select pg_terminate_backend('进程ID');