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From: Srinath Reddy Sadipiralla <srinath2133@gmail.com>
Date: Tue, 24 Mar 2026 16:25:47 +0530
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 <CAFC+b6rYYQ6CqXYYsmnLeWsCe7mDa9PhbM8=KYFB0X+XOYexEg@mail.gmail.com>
Subject: Re: Teach isolation tester about injection points in background
 workers
To: Antonin Houska <ah@cybertec.at>
Cc: pgsql-hackers@lists.postgresql.org
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Hi Antonin,

On Mon, Mar 23, 2026 at 12:52=E2=80=AFPM Antonin Houska <ah@cybertec.at> wr=
ote:

> I hit a limitation of the isolation tester when trying to reproduce a bug
> in
> REPACK (CONCURRENTLY) [1]: it does not recognize that session is blocked
> due
> to background worker waiting on an injection point. This patch tries to f=
ix
> that.
>

+1. I was thinking can we move the logic of checking if bg workers are the
reason of blocking the main backend
inside pg_isolation_test_session_is_blocked
to make it cleaner, and regarding "XXX Should we use a separate query for
that?"
i am confused here IIUC if we keep it as 1 query using UNION every time its
for sure
that both the queries will run, which can increase more execution time but
less libpq/socket
calls, but if we send as 2 queries if 1st query doesn't returns true we
have to go and
check the other query, so here if 2 queries ran then execution +
libpq/socket calls overhead,
so i am slightly inclined towards separating the queries , so that if 1st
gets satisfied then
we don't touch the 2nd query at all, please correct me if i am wrong here :=
)


--=20
Thanks,
Srinath Reddy Sadipiralla
EDB: https://www.enterprisedb.com/

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<div dir=3D"ltr"><div dir=3D"ltr">Hi=C2=A0Antonin,</div><br><div class=3D"g=
mail_quote gmail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On =
Mon, Mar 23, 2026 at 12:52=E2=80=AFPM Antonin Houska &lt;<a href=3D"mailto:=
ah@cybertec.at">ah@cybertec.at</a>&gt; wrote:<br></div><blockquote class=3D=
"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(2=
04,204,204);padding-left:1ex">I hit a limitation of the isolation tester wh=
en trying to reproduce a bug in<br>
REPACK (CONCURRENTLY) [1]: it does not recognize that session is blocked du=
e<br>
to background worker waiting on an injection point. This patch tries to fix=
<br>
that.<br></blockquote><div><br>+1. I was thinking can we move the logic of =
checking if bg workers are the<br>reason of blocking the main backend insid=
e=C2=A0pg_isolation_test_session_is_blocked<br>to make it cleaner, and rega=
rding &quot;XXX Should we use a separate query for that?&quot;<br>i am conf=
used here IIUC if we keep it as 1 query using UNION every time its for sure=
<br>that both the queries will run, which can increase more execution time =
but less libpq/socket<br>calls, but if we send as 2 queries if 1st query do=
esn&#39;t returns true we have to go and<br>check the other query, so here =
if 2 queries ran then execution=C2=A0+ libpq/socket calls overhead,<br>so i=
 am slightly inclined towards separating the queries , so that if 1st gets =
satisfied then<br>we don&#39;t touch the 2nd query at all, please correct m=
e if i am wrong here :)<br><br></div></div><div><br clear=3D"all"></div><di=
v><br></div><span class=3D"gmail_signature_prefix">-- </span><br><div dir=
=3D"ltr" class=3D"gmail_signature"><div dir=3D"ltr"><span style=3D"color:rg=
b(34,34,34)">Thanks,</span><br style=3D"color:rgb(34,34,34)"><span style=3D=
"color:rgb(34,34,34)">Srinath Reddy Sadipiralla</span><br style=3D"color:rg=
b(34,34,34)"><span style=3D"color:rgb(34,34,34)">EDB:=C2=A0</span><a href=
=3D"https://www.enterprisedb.com/" style=3D"color:rgb(17,85,204)" target=3D=
"_blank">https://www.enterprisedb.com/</a></div></div></div>

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