| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | Corey Huinker <corey(dot)huinker(at)gmail(dot)com> |
| Cc: | Stephen Frost <sfrost(at)snowman(dot)net>, Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, Peter Smith <smithpb2250(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Subject: | Re: Statistics Import and Export |
| Date: | 2024-03-30 17:01:54 |
| Message-ID: | c3bc9b9eab819d9c6077b29588fca333ee2cbd80.camel@j-davis.com |
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On Sat, 2024-03-30 at 01:34 -0400, Corey Huinker wrote:
>
> - 002pg_upgrade.pl now dumps before/after databases with --no-
> statistics. I tried to find out why some tables were getting their
> relstats either not set, or set and reset, never affecting the
> attribute stats. I even tried turning autovacuum off for both
> instances, but nothing seemed to change the fact that the same tables
> were having their relstats reset.
I think I found out why this is happening: a schema-only dump first
creates the table, then sets the relstats, then creates indexes. The
index creation updates the relstats, but because the dump was schema-
only, it overwrites the relstats with zeros.
That exposes an interesting dependency, which is that relstats must be
set after index creation, otherwise they will be lost -- at least in
the case of pg_upgrade.
This re-raises the question of whether stats are part of a schema-only
dump or not. Did we settle conclusively that they are?
Regards,
Jeff Davis
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