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Tue, 12 May 2026 06:59:16 -0700 (PDT) MIME-Version: 1.0 References: <19473-92f01422b9220412@postgresql.org> In-Reply-To: From: Kirill Reshke Date: Tue, 12 May 2026 18:59:03 +0500 X-Gm-Features: AVHnY4LM8RyVWQ0b_70IJJym_PEQvZZqQAoUvOhC-qpaQ6nymn5JWyjeANd9_ZE Message-ID: Subject: Re: BUG #19473: regression error in dblink: another command is already in progress To: Fujii Masao Cc: o15611@gmail.com, PostgreSQL mailing lists Content-Type: multipart/alternative; boundary="000000000000cf1a0a06519f44d2" List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Archived-At: Precedence: bulk --000000000000cf1a0a06519f44d2 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 12 May 2026, 18:47 Fujii Masao, wrote: > On Sat, May 9, 2026 at 4:43=E2=80=AFAM PG Bug reporting form > 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=3Dpostgres user=3Dpostgres', $$ select 7; = $$ ) > as > > (col1 int); > > SELECT * FROM dblink_connect('connection1', 'host=3D/var/run/postgresql > > port=3D5432'); > > 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 f= or > 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 b= e > 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? > --000000000000cf1a0a06519f44d2 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On Tue, 12 May 2026, 18:47 Fujii= Masao, <masao.fujii@gmail.com<= /a>> wrote:
On Sat, May 9, 2026 = at 4:43=E2=80=AFAM PG Bug reporting form
<noreply@postgresql.org> wrote:
>
> The following bug has been logged on the website:
>
> Bug reference:=C2=A0 =C2=A0 =C2=A0 19473
> Logged by:=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 Oleg Ivanov
> Email address:=C2=A0 =C2=A0 =C2=A0 o15611@gmail.com
> PostgreSQL version: 18.3
> Operating system:=C2=A0 =C2=A0Linux
> Description:
>
> Testcase:
> SELECT * FROM dblink('dbname=3Dpostgres user=3Dpostgres', $$ s= elect 7; $$ ) as
> (col1 int);
> SELECT * FROM dblink_connect('connection1', 'host=3D/var/r= un/postgresql
> port=3D5432');
> SELECT * FROM dblink_send_query('connection1', $$ select 8 fro= m pg_sleep(1);
> $$ );
> 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');
>
>=C2=A0 col1
> ------
>=C2=A0 =C2=A0 =C2=A07
> (1 row)
>
>=C2=A0 dblink_connect
> ----------------
>=C2=A0 OK
> (1 row)
>
>=C2=A0 dblink_send_query
> -------------------
>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 1
> (1 row)
>
>=C2=A0 dblink_is_busy
> ----------------
>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A01
> (1 row)
>
>=C2=A0 col1
> ------
>=C2=A0 =C2=A0 =C2=A08
> (1 row)
>
> ERROR:=C2=A0 another command is already in progress
> CONTEXT:=C2=A0 while executing command on dblink connection named &quo= t;connection1"
>=C2=A0 dblink_disconnect
> -------------------
>=C2=A0 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 onc= e 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 th= at
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 t= o 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 connectio= n state. Is this OK?
--000000000000cf1a0a06519f44d2--