Re: Index Partition Size Double of its Table Partition?

On Wed, Oct 30, 2024 at 10:35 AM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:

> On Wed, Oct 30, 2024 at 11:24 AM Don Seiler <don(at)seiler(dot)us> 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