I think I should also report it as a bug since logically, it couldn't exist.
On Wed, Dec 18, 2019 at 1:04 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Kaijiang Chen <chenkaijiang(at)gmail(dot)com> writes:
> > I'm using postgres 9.4.17 on centos 7.
> > I check the running queries with the following SQL:
> > SELECT
> > procpid,
> > start,
> > now() - start AS lap,
> > current_query
> > FROM
> > (SELECT
> > backendid,
> > pg_stat_get_backend_pid(S.backendid) AS procpid,
> > pg_stat_get_backend_activity_start(S.backendid) AS start,
> > pg_stat_get_backend_activity(S.backendid) AS current_query
> > FROM
> > (SELECT pg_stat_get_backend_idset() AS backendid) AS S
> > ) AS S
> > WHERE
> > current_query <> '<IDLE>'
> > ORDER BY
> > lap DESC;
>
> Don't know where you got this query from, but it's wrong for any PG
> version more recent than (I think) 9.1. We don't use "<IDLE>" as an
> indicator of idle sessions anymore; rather, those can be identified
> by having state = 'idle'. What's in the query column for such a session
> is its last query.
>
> > Then, I found a SQL that has run for some days (and still running):
> > procpid | 32638
> > start | 2019-11-25 16:29:29.529318+08
> > lap | 21 days 18:24:54.707369
> > current_query | DEALLOCATE pdo_stmt_00000388
>
> It's not running. That was the last query it ran, back in November :-(
> You could zap the session with pg_terminate_backend(), but
> pg_cancel_backend() is not going to have any effect because there's
> no active query.
>
> regards, tom lane
>