Postgresql 后端启动如何比xact启动更好
后端启动时间如何超过xact\U启动/查询\U启动的2天?第三节看起来不错,但前两节看起来很奇怪,这可能吗?这有什么意义吗Postgresql 后端启动如何比xact启动更好,postgresql,Postgresql,后端启动时间如何超过xact\U启动/查询\U启动的2天?第三节看起来不错,但前两节看起来很奇怪,这可能吗?这有什么意义吗 pg=> select * from pg_catalog.pg_stat_activity where usename = 'etl_user' and state = 'active' and backend_xmin = 65201266; datid | datname | pid |usesysid | usename |
pg=> select * from pg_catalog.pg_stat_activity where usename = 'etl_user' and state = 'active' and backend_xmin = 65201266;
datid | datname | pid |usesysid | usename | application_name | client_addr | client_hostname | client_port | backend_start | xact_start | query_start | state_change | wait_event_type | wait_event| state | backend_xid | backend_xmin | query | backend_type
-------+---------+-------+----------+----------+------------------------+----------------+-----------------+-------------+-------------------------------+-------------------------------+-------------------------------+-------------------------------+-----------------+------------+--------+-------------+--------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------
16408 | pg| 37908 | 229661 | etl_user | PostgreSQL JDBC Driver | | | | 2021-04-20 21:36:22.540271+00 | 2021-04-17 22:31:32.314106+00 | 2021-04-17 22:31:32.317577+00 | 2021-04-20 21:36:22.541472+00 | || active | | 65201266 | SELECT 1 FROM (SELECT ...) | parallel worker
16408 | pg| 37909 | 229661 | etl_user | PostgreSQL JDBC Driver | | | | 2021-04-20 21:36:22.540909+00 | 2021-04-17 22:31:32.314106+00 | 2021-04-17 22:31:32.317577+00 | 2021-04-20 21:36:22.542134+00 | || active | | 65201266 | SELECT 1 FROM (SELECT ...) | parallel worker
16408 | pg| 3601 | 229661 | etl_user | PostgreSQL JDBC Driver | 10.175.130.142 | | 49832 | 2021-04-17 22:31:32.232008+00 | 2021-04-17 22:31:32.314106+00 | 2021-04-17 22:31:32.317577+00 | 2021-04-17 22:31:32.317578+00 | || active | | 65201266 | SELECT 1 FROM (SELECT ...) | client backend
(3 rows)
是的,看起来不可能
我唯一的解释是,自会话开始以来,有人更改了系统时间。在我看来,这些是为帮助领导者而启动的并行工作程序,它们继承了领导者xact_start,但不是后端_start。查看pg_stat_activity中的其余列并了解其版本会有所帮助。好的,这是在aws aurora postgresql上,我不知道后端是否发生了更改:-)用所有列更新了帖子,版本是11.6,你是对的-他们是并行工作程序。但是一个查询可以在开始执行查询的两天后启动并行工作程序吗?我不知道为什么它会在这么长时间后启动并行工作程序。看到对这个问题的解释可能会提供一些启示。也许有些不能并行的任务必须先完成?