Re: BUG #19488: Standby connection fails after dropping on login event trigger enabled always

On Wed, May 20, 2026 at 8:31 PM Alexander Korotkov <aekorotkov(at)gmail(dot)com> wrote:
>
> On Wed, May 20, 2026 at 1:03 PM Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
> > On Wed, May 20, 2026 at 1:37 PM Ayush Tiwari
> > <ayushtiwari(dot)slg01(at)gmail(dot)com> wrote:
> > > Thanks for the report and the precise repro.
> >
> > +1
> >
> > > Attached patch adds a RecoveryInProgress() check to skip the cleanup
> > > branch on standbys.
> >
> > Thanks for investigating this issue and for the patch!
> > The patch looks good to me.
> >
> > > I think this needs to be backpatched too.
> >
> > Yes. Seems this should be backpatched to v17, where login event triggers
> > were introduced.
>
> I've added a tap test reproducing the bug. I'm going to push and
> backpatch this to v17 if no objections.

+# Wait for the standby to replay the CREATE/DROP catalog state. At
+# this point the standby's pg_database.dathasloginevt is still true.
+$primary->wait_for_replay_catchup($standby);
+
+# A new connection to the standby exercises EventTriggerOnLogin()'s
+# cleanup branch. With the RecoveryInProgress() guard, that branch is
+# skipped on the standby and the connection succeeds. Without it the
+# session aborts with a FATAL about AccessExclusiveLock. Probing the
+# flag itself via safe_psql is what triggers the cleanup path.
+is( $standby->safe_psql(
+ 'postgres',
+ "SELECT dathasloginevt FROM pg_database WHERE datname = 'postgres'"),
+ 't',
+ 'standby accepts connection and reports dangling dathasloginevt');

The test looks unstable to me. wait_for_replay_catchup() may connect to
the primary to obtain the flush LSN, which could cause dathasloginevt to
become false before the subsequent safe_psql() call on the standby.

Regards,

--
Fujii Masao