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From: Durgamahesh Manne <maheshpostgres9@gmail.com>
Date: Fri, 11 Oct 2024 18:01:58 +0530
Message-ID: <CAJCZko+-DCLp75-9JvkYxjrnvFqCA++VN1yLhFgwCYJWvqp8rA@mail.gmail.com>
Subject: Re: Question on indexes
To: Greg Sabino Mullane <htamfids@gmail.com>
Cc: sud <suds1434@gmail.com>, Erik Wienhold <ewie@ewie.name>, xof@thebuild.com, 
	pgsql-general <pgsql-general@lists.postgresql.org>
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On Fri, Oct 11, 2024 at 5:00=E2=80=AFPM Greg Sabino Mullane <htamfids@gmail=
.com>
wrote:

> if we have any column with large string/text values and we want it to be
>> indexed then there is no choice but to go for a hash index. Please corre=
ct
>> me if I'm wrong.
>>
>
> There are other strategies / solutions, but we would need to learn more
> about your use case.
>
> Cheers,
> Greg
>
>

Hi Respected Team

How do we enforce the secondary column of composite index to index scan on
concurrent activity in postgres?
Second column of composite index not in use effectively with index scan
when using second column at where clause

I have composite index on (placedon,id) of test
When querying  select * from test where id =3D '4234';
Value of id changes and during concurrent activity and cpu utilization
increased too much  that i have observed which means query plan changed why

I could see index scan with explain for it  on singal call or double calls

Is there any way to keep an index scan for it during concurrency rather
than a separate index on the second column of the composite index ?


Regards,
Durga Mahesh

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote">=
<div dir=3D"ltr" class=3D"gmail_attr">On Fri, Oct 11, 2024 at 5:00=E2=80=AF=
PM Greg Sabino Mullane &lt;<a href=3D"mailto:htamfids@gmail.com">htamfids@g=
mail.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-le=
ft:1ex"><div dir=3D"ltr"><div class=3D"gmail_quote"><blockquote class=3D"gm=
ail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,=
204,204);padding-left:1ex"><div dir=3D"ltr"><div class=3D"gmail_quote">if w=
e have any column with large string/text values and we want it to be indexe=
d then there is no choice but to go for a hash index. Please correct me if =
I&#39;m wrong.<br></div></div></blockquote><div><br></div><div>There are ot=
her strategies / solutions, but we would need to learn more about your use =
case.</div><div><br></div><div>Cheers,</div><div>Greg</div><div>=C2=A0</div=
></div></div></blockquote><div><br></div><div>Hi Respected Team</div><div><=
br></div>How do we enforce the secondary column of composite index to index=
 scan on concurrent activity in postgres?=C2=A0=C2=A0<br><div><div dir=3D"a=
uto">Second column of composite index not in use effectively with index sca=
n=C2=A0 when using second column at where clause</div><div dir=3D"auto"><br=
></div><div dir=3D"auto">I have composite index on (placedon,id) of test=C2=
=A0</div><div dir=3D"auto">When querying=C2=A0 select * from test where id =
=3D &#39;4234&#39;;</div><div dir=3D"auto">Value of id changes and during c=
oncurrent activity and cpu utilization increased too much=C2=A0 that i have=
 observed which means query plan changed why</div><div dir=3D"auto"><br></d=
iv><div dir=3D"auto">I could see index scan with explain for it=C2=A0 on si=
ngal call or double calls</div><div dir=3D"auto"><br></div><div dir=3D"auto=
">Is there any way to keep an index scan for it during concurrency rather t=
han a separate index on the second column of the composite index ?</div><di=
v dir=3D"auto"><br></div><div dir=3D"auto"><br></div><div dir=3D"auto">Rega=
rds,</div></div><div>Durga Mahesh=C2=A0=C2=A0</div></div></div>

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