Thread: [BeginnerQuestion]Why these is 6 rows in my SELECT statement?
Hello community,
I am checking my pg_stat_activity view,but something confused me.
Just like this:
postgres=# SELECT wait_event_type, wait_event FROM pg_stat_activity;
wait_event_type | wait_event
-----------------+---------------------
Activity | AutoVacuumMain
Activity | LogicalLauncherMain
|
Activity | BgWriterHibernate
Activity | CheckpointerMain
Activity | WalWriterMain
(6 rows)
As you can see, the third row is empty,but I don't know why.
Can anyone provide some solution to me?
Thanks in advance!
Yours,
BeginnerC.
2022年9月8日(木) 17:37 BeginnerC <chuxuec@outlook.com>: > > Hello community, > I am checking my pg_stat_activity view,but something confused me. > Just like this: > > postgres=# SELECT wait_event_type, wait_event FROM pg_stat_activity; > wait_event_type | wait_event > -----------------+--------------------- > Activity | AutoVacuumMain > Activity | LogicalLauncherMain > | > Activity | BgWriterHibernate > Activity | CheckpointerMain > Activity | WalWriterMain > (6 rows) > > As you can see, the third row is empty,but I don't know why. > Can anyone provide some solution to me? It's empty because that's your own client session and it's not waiting on anything :). postgres=# SELECT pg_backend_pid(); pg_backend_pid ---------------- 24941 (1 row) postgres=# SELECT pid, backend_type, wait_event_type, wait_event FROM pg_stat_activity; pid | backend_type | wait_event_type | wait_event -------+------------------------------+-----------------+--------------------- 20859 | autovacuum launcher | Activity | AutoVacuumMain 20860 | logical replication launcher | Activity | LogicalLauncherMain 21554 | walsender | Activity | WalSenderMain 24941 | client backend | | 20856 | background writer | Activity | BgWriterHibernate 20855 | checkpointer | Activity | CheckpointerMain 20858 | walwriter | Activity | WalWriterMain (7 rows) Regards Ian Barwick
Re: [BeginnerQuestion]Why these is 6 rows in my SELECT statement?
From
hubert depesz lubaczewski
Date:
On Thu, Sep 08, 2022 at 04:37:00PM +0800, BeginnerC wrote: > Hello community, > I am checking my pg_stat_activity view,but something confused me. > Just like this: > > postgres=# SELECT wait_event_type, wait_event FROM pg_stat_activity; > wait_event_type | wait_event > -----------------+--------------------- > Activity | AutoVacuumMain > Activity | LogicalLauncherMain > | > Activity | BgWriterHibernate > Activity | CheckpointerMain > Activity | WalWriterMain > (6 rows) > > As you can see, the third row is empty,but I don't know why. > Can anyone provide some solution to me? > Thanks in advance! Please do: \pset null '-- null --' SELECT wait_event_type, wait_event FROM pg_stat_activity; it will most likely show -- null -- in these fields. which means values in these columns are null.SELECT wait_event_type, wait_event FROM pg_stat_activity; You can find more about this/these backends by doing: select * from pg_stat_activity where wait_event_type is null \gx depesz