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From: Don Seiler <[email protected]>
To: Peter Geoghegan <[email protected]>
Cc: Postgres General <[email protected]>
Subject: Re: Index Partition Size Double of its Table Partition?
Date: Wed, 30 Oct 2024 10:39:28 -0500
Message-ID: <CAHJZqBBrXD5ca+BcoKSg0yBbehtos9Zt+zd0gN1J2L6xP+4jJg@mail.gmail.com> (raw)
In-Reply-To: <CAH2-Wzmq+ZLkYFLq-WGJhd=xJ0UosQMuLCMbHXKcKucwsSL=eg@mail.gmail.com>
References: <CAHJZqBA83fBGjqXqF+rVbErdy2N0_zDEiLWJMrDUSKjKQOZi3Q@mail.gmail.com>
	<CAH2-Wzmq+ZLkYFLq-WGJhd=xJ0UosQMuLCMbHXKcKucwsSL=eg@mail.gmail.com>

On Wed, Oct 30, 2024 at 10:35 AM Peter Geoghegan <[email protected]> wrote:

> On Wed, Oct 30, 2024 at 11:24 AM Don Seiler <[email protected]> wrote:
> > One thing worth mentioning is that the table is 4 columns, the index is
> on two of them and includes the other two. I can't think of an explanation
> for the index being so much larger than its table, especially compared to
> last month's index.
> >
> > Curious if anyone has any thoughts on what might be causing this.
>
> You mentioned that this has 4 columns. Sounds like this could be a
> "locally monotonically increasing index". I wonder if you're
> benefiting from this optimization, though only inconsistently:
>
> https://www.youtube.com/watch?v=p5RaATILoiE&t=2079s
> https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=f21668f3
>
> Of course, this is only a guess. I vaguely recall a complaint that
> sounded vaguely like yours, also involving partitioning.
>

Thanks Peter, I'll look into that shortly.

I should have also included that this is on PG 15 (currently 15.8 but we
created the indexes when it was still 15.7) on Ubuntu 22.04 LTS.

Don.

-- 
Don Seiler
www.seiler.us


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