Re: BUG #19473: regression error in dblink: another command is already in progress

On Tue, 12 May 2026, 18:47 Fujii Masao, <masao.fujii@gmail.com> wrote:

> On Sat, May 9, 2026 at 4:43 AM PG Bug reporting form
> <noreply@postgresql.org> wrote:
> >
> > The following bug has been logged on the website:
> >
> > Bug reference:      19473
> > Logged by:          Oleg Ivanov
> > Email address:      o15611@gmail.com
> > PostgreSQL version: 18.3
> > Operating system:   Linux
> > Description:
> >
> > Testcase:
> > SELECT * FROM dblink('dbname=postgres user=postgres', $$ select 7; $$ )
> as
> > (col1 int);
> > SELECT * FROM dblink_connect('connection1', 'host=/var/run/postgresql
> > port=5432');
> > SELECT * FROM dblink_send_query('connection1', $$ select 8 from
> pg_sleep(1);
> > $$ );
> > SELECT dblink_is_busy('connection1');
> > SELECT * FROM dblink_get_result('connection1') as t(col1 int);
> > --- SELECT dblink_is_busy('connection1');
> > SELECT * FROM dblink_exec('connection1', $$ CHECKPOINT; $$);
> > SELECT * FROM dblink_disconnect('connection1');
> >
> >  col1
> > ------
> >     7
> > (1 row)
> >
> >  dblink_connect
> > ----------------
> >  OK
> > (1 row)
> >
> >  dblink_send_query
> > -------------------
> >                  1
> > (1 row)
> >
> >  dblink_is_busy
> > ----------------
> >               1
> > (1 row)
> >
> >  col1
> > ------
> >     8
> > (1 row)
> >
> > ERROR:  another command is already in progress
> > CONTEXT:  while executing command on dblink connection named
> "connection1"
> >  dblink_disconnect
> > -------------------
> >  OK
> > (1 row)
> >
> > There was no error in 16 version. The error appeared in 17 version. It
> > seems, there is a regression bug.
> > The workaround is to uncomment a commented statement.
>
> The documentation for dblink_get_result() notes "It must be called once for
> each query sent, and one additional time to obtain an empty set result,
> before the connection can be used again". So in your case, it seems that
> dblink_get_result() needs to be called one more time before calling
> dblink_exec(). If you do that, I think that the error "another command is
> already in progress" should not occur. Therefore, this does not seem to be
> a bug to me. Thought?
>
> Regards,
>
> --
> Fujii Masao
>


Doesn't dblink_is_busy violates this doc then? I mean, dblink_is_busy has
side effect of changing connection state. Is this OK?

>