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 <4794e640-e4a4-4730-985a-57be297122e0@aklaver.com>
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From: veem v <veema0000@gmail.com>
Date: Fri, 5 Sep 2025 02:02:28 +0530
Message-ID: <CAB+=1TV0ywL3kCnVO-MA8XDWzrMRB5m5ZC9jADPwT=o-YECKwA@mail.gmail.com>
Subject: Re: Debugging query performance in postgres
To: Adrian Klaver <adrian.klaver@aklaver.com>
Cc: pgsql-general <pgsql-general@lists.postgresql.org>
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On Thu, 4 Sept 2025 at 23:19, Adrian Klaver <adrian.klaver@aklaver.com>
wrote:

> On 9/4/25 09:57, veem v wrote:
> > Hello,
> > We have a situation in which we had a dml query within a procedure that
> > was running fine but suddenly the plan flipped and it started running
> > longer. It took us a good amount of time to identify the cause and fix
> > it. So I have below questions,
>
> What was the cause?
>
> Postgres version
>
> Was there any major changes in the database e.g schema changes or
> quantity of data?
>
> Is autovacuum running?
>
> > 1)Do we have any data dictionary view or query available which gives us
> > information on what were the queryids those are executing from within a
> > procedure and how much time they are taking?
> > 2)Also how to identify , if any specific queries has opted a different
> > plan today as compared to past executions and also response time
> > increased because of that?
>
> Take a look at:
>
> https://www.postgresql.org/docs/current/pgstatstatements.html
>
>
We didn't get the exact root cause why the plan flipped but we have to add
additional filters to get rid of the performance issue.
The version is 16.
Yes, autovacuum running.
We don't have any major changes. But if there was a significant change in
quantity of data , Yet to check that.

The pg_stats_statement does show the execution stats of the individual
query execution , but doesnt show any historical plan deviation. Also the
individual procedure and sql statement are logged into this view but i was
wondering if there is an easy way to relate the sql text of the procedure
with the underlying sqls running within the procedure?

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><div class=3D"gmail_quote gmail=
_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Thu, 4 Sept 2025=
 at 23:19, Adrian Klaver &lt;<a href=3D"mailto:adrian.klaver@aklaver.com">a=
drian.klaver@aklaver.com</a>&gt; wrote:<br></div><blockquote class=3D"gmail=
_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204=
,204);padding-left:1ex">On 9/4/25 09:57, veem v wrote:<br>
&gt; Hello,<br>
&gt; We have a situation in which we had a dml query within a procedure tha=
t <br>
&gt; was running fine but suddenly the plan flipped and it started running =
<br>
&gt; longer. It took us a good amount of time to identify the cause and fix=
 <br>
&gt; it. So I have below questions,<br>
<br>
What was the cause?<br>
<br>
Postgres version<br>
<br>
Was there any major changes in the database e.g schema changes or <br>
quantity of data?<br>
<br>
Is autovacuum running?<br>
<br>
&gt; 1)Do we have any data dictionary view or query available which gives u=
s <br>
&gt; information on what were the queryids those are executing from within =
a <br>
&gt; procedure and how much time they are taking?<br>
&gt; 2)Also how to identify , if any specific queries has opted a different=
 <br>
&gt; plan today as compared to past executions and also response time <br>
&gt; increased because of that?<br>
<br>
Take a look at:<br>
<br>
<a href=3D"https://www.postgresql.org/docs/current/pgstatstatements.html" r=
el=3D"noreferrer" target=3D"_blank">https://www.postgresql.org/docs/current=
/pgstatstatements.html</a><br><br></blockquote><div><br></div><div>We didn&=
#39;t=C2=A0get the exact=C2=A0root cause why the plan flipped but we have t=
o add additional filters to get rid of the performance issue.</div><div>The=
 version is 16.</div><div>Yes, autovacuum running.</div><div>We don&#39;t=
=C2=A0have any major changes. But if there was a significant change in quan=
tity of data , Yet to check that.</div><div><br></div><div>The pg_stats_sta=
tement does show the execution stats of the individual query execution , bu=
t doesnt show any historical plan deviation. Also the individual procedure =
and sql statement are logged into this view but i was wondering if there is=
 an easy way to relate the sql text of the procedure with the underlying sq=
ls running within the procedure?</div></div></div>

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