Re: pg_stat_activity.query empty

2022年4月26日(火) 23:24 Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>:
>
> On Tue, 2022-04-26 at 06:59 -0700, David G. Johnston wrote:
> > On Tue, Apr 26, 2022 at 6:55 AM Robert Lichtenberger <r(dot)lichtenberger(at)synedra(dot)com> wrote:
> > > When executing "SELECT * FROM pg_stat_activity" I get lots of rows that
> > > have an empty "query" column.
> > >
> > > According to [1] this column should contain the "Text of this backend's
> > > most recent query", either a query that is currently running or the last
> > > query that was executed.
> > >
> > > So how comes that a lot of the rows in pg_stat_activity have an empty
> > > "query"?
> > >
> > > https://www.postgresql.org/docs/current/monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW
> >
> > They've never executed a query. Probably due to connection pooling opening connections for the pool but never needing to hand them out.
>
> An alternative option is that the last query sent was an empty string.

Or it's the kind of backend which doesn't normally execute queries.

epp=# SELECT backend_type FROM pg_stat_activity WHERE query = '';
backend_type
------------------------------
autovacuum launcher
pglogical supervisor
logical replication launcher
pglogical manager 16389
background writer
checkpointer
walwriter
(7 rows)

Regards

Ian Barwick

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