| From: | Corey Huinker <corey(dot)huinker(at)gmail(dot)com> |
|---|---|
| To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)anarazel(dot)de>, Michael Paquier <michael(at)paquier(dot)xyz>, jian he <jian(dot)universality(at)gmail(dot)com>, Nathan Bossart <nathandbossart(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, Stephen Frost <sfrost(at)snowman(dot)net>, Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>, Peter Smith <smithpb2250(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, alvherre(at)alvh(dot)no-ip(dot)org |
| Subject: | Re: Statistics Import and Export |
| Date: | 2025-02-24 19:03:51 |
| Message-ID: | CADkLM=f9CDaTFg=mvurE4o4X14wxes-T8=QP0oKRmK+swJcY9Q@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Feb 24, 2025 at 1:54 PM Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
> On Mon, 2025-02-24 at 13:47 -0500, Corey Huinker wrote:
> > There doesn't seem to be any way around it, but it will
> > slightly complicate the dump-ing side of things, in that we need to
> > either:
> >
> > a) switch to attnums for index expressions and keep attname calls for
> > everything else.
>
> The only stats for indexes are on expression columns, so AFAICT there's
> no difference between the above description and "use attnums for
> indexes and attnames for tables". Either way, I agree that's the way to
> go.
>
That's true now, but may not be in the future, like if we started keeping
separate stats for partial indexes.
>
> We certainly want attnames for tables to keep it working reasonably
> well for cases where the user might be doing something more interesting
> than a binary upgrade, as you point out. But attribute numbers for
> indexes seem much more reliable: an index with a different attribute
> order is a fundamentally different index.
Sadly, that attnum isn't available in pg_stats, so we'd have to reintroduce
the joins to pg_namespace and pg_class to get at pg_attribute, at least for
indexes.
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