目录
环境
症状
问题原因
解决方案
环境
系统平台：N/A
版本：6.0
症状
数据库锁表后，对锁住的表无法进行改动，严重时会影响业务正常运转。
问题原因
多个会话在同一时间段对相同的数据做了改动，且第一个会话没有立即释放。
解决方案
1、创建测试表
highgo=# select * from hgjob_test033;
id | name | timestart | count
----+-------+----------------------------+-------
1 | job02 | 2021-03-05 17:44:40.885468 | 5
2 | job02 | 2021-03-05 17:55:30.621806 | 5
3 | job02 | 2021-03-05 17:59:24.859304 | 5
4 | job02 | 2021-03-05 17:59:24.859304 | 5
5 | job02 | 2021-03-05 17:59:24.859304 | 5
6 | job02 | 2021-03-05 17:59:24.859304 | 5
7 | job02 | 2021-03-05 17:59:24.859304 | 5
(7 rows)
2、模拟锁情况
窗口一：
highgo=# begin;
BEGIN
highgo=# update hgjob_test033 set name = 'newjob3' where id=2;
UPDATE 1
窗口二：
highgo=# begin ;
BEGIN
highgo=# update hgjob_test033 set name = 'newjob4' where id=2;
【此时会一直卡住不动】
窗口三：
创建锁状态视图
create view viewlocks as
SELECT
waiting.locktype AS waiting_locktype, --可锁定对象的类型：relation, extend, page, tuple,transactionid, virtualxid,object, userlock, advisory
waiting.relation::regclass AS waiting_table, --等待表
waiting_stm.query AS waiting_query, --等待查询
waiting.mode AS waiting_mode, --这个进程持有的或者是期望持有的锁模式
waiting.pid AS waiting_pid, --持有或者等待这个锁的服务器进程的进程ID ，如果锁是被一个预备事务持有的，那么为空
other.locktype AS previous_locktype, --当前锁的上层锁
other.relation::regclass AS previous_table,
other_stm.query AS previous_query,
other_stm.state AS previous_state,
other.mode AS Previous_mode,
other.pid AS previous_pid, --等待该pid完成（kill）
other.GRANTED AS previous_granted --如果持有锁，为真，如果等待锁，为假
FROM
pg_catalog.pg_locks AS waiting
JOIN
pg_catalog.pg_stat_activity AS waiting_stm
ON (
waiting_stm.pid = waiting.pid
)
JOIN
pg_catalog.pg_locks AS other
ON (
(
waiting."database" = other."database"
AND waiting.relation = other.relation
)
OR waiting.transactionid = other.transactionid
)
JOIN
pg_catalog.pg_stat_activity AS other_stm
ON (
other_stm.pid = other.pid
)
WHERE
NOT waiting.GRANTED
AND
waiting.pid <> other.pid;
3、查询锁状态
highgo=# select * from viewlocks;
waiting_locktype | waiting_table | waiting_query | waiting_mode | waiting_pid | previous_locktype | previous_table |
previous_query | previous_state | previous_mode | previous_pid | previous_granted
------------------+---------------+-------------------------------------------------------+--------------+-------------+-------------------+----------------+----
---------------------------------------------------+---------------------+---------------+--------------+------------------
transactionid | | update hgjob_test033 set name = 'newjob4' where id=2; | ShareLock | 4384 | transactionid | | upd
ate hgjob_test033 set name = 'newjob3' where id=2; | idle in transaction | ExclusiveLock | 4207 | t
(1 row)
4、取消对应操作进程
highgo=# select pg_cancel_backend(4384);
pg_cancel_backend
-------------------
t
(1 row)
日志打印：
ERROR: canceling statement due to user request
CONTEXT: while updating tuple (0,2) in relation "hgjob_test033"
数据状态：
highgo=# select * from hgjob_test033;
id | name | timestart | count
----+---------+----------------------------+-------
1 | job02 | 2021-03-05 17:44:40.885468 | 5
3 | job02 | 2021-03-05 17:59:24.859304 | 5
4 | job02 | 2021-03-05 17:59:24.859304 | 5
5 | job02 | 2021-03-05 17:59:24.859304 | 5
6 | job02 | 2021-03-05 17:59:24.859304 | 5
7 | job02 | 2021-03-05 17:59:24.859304 | 5
2 | newjob3 | 2021-03-05 17:55:30.621806 | 5
(7 rows)