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From: Durgamahesh Manne <[email protected]>
To: David Rowley <[email protected]>
Cc: PostgreSQL mailing lists <[email protected]>
Cc: Greg Sabino Mullane <[email protected]>
Subject: Re: Inefficient use of index scan on 2nd column of composite index during concurrent activity
Date: Tue, 15 Oct 2024 15:44:26 +0530
Message-ID: <CAJCZkoJEWdn3B57AWcnNn_4xycO33iKiUZZRXcy8EqyRHLv8fw@mail.gmail.com> (raw)
In-Reply-To: <CAApHDvpy1Goh=tmZKDvJ+3Uqb69r8i3U09_m9+P4NBertCyVmw@mail.gmail.com>
References: <CAJCZkoL3E5M7taGpdtJRhwM0zCQ1-T2uzv4FKj_Arrz-fRusOQ@mail.gmail.com>
	<CAJCZkoKEA4ZcYq0ereB2vFUQ+RQ8o2CEAUu5a4p-_ijuUvFL0g@mail.gmail.com>
	<CAApHDvpy1Goh=tmZKDvJ+3Uqb69r8i3U09_m9+P4NBertCyVmw@mail.gmail.com>

On Tue, 15 Oct, 2024, 15:15 David Rowley, <[email protected]> wrote:

> On Sat, 12 Oct 2024 at 02:28, Durgamahesh Manne
> <[email protected]> wrote:
> > 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 quering  select * from test where id = '4234';
> > Value of id changes and during concurrent activity and cpu utilization
> increased toomuch  that i have observed which means query plan changed why
> >
> > I could see index scan with explain for it
> >
> > Is there any way to keep index scan for it during even on concurrency
> rather than seperate index on second column of composite index ?
>
> It sounds like you might be asking about something we call "index skip
> scans". Currently, PostgreSQL does not support these, however there is
> work being done to add support and that might arrive in PG18.
>
> There is some information about a possible workaround in [1] which may
> be of use to you.
>
> David
>
> [1] https://wiki.postgresql.org/wiki/Loose_indexscan


Hi David

Thanks you for valuable info

Regards,
Durga Mahesh

>
>

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