pg.ddx.io pgsql-hackers@postgresql.org mailing list archive help / color / mirror / Atom feed From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jeff Davis <pgsql@j-davis.com>
Cc: Corey Huinker <corey.huinker@gmail.com>
Cc: Magnus Hagander <magnus@hagander.net>
Cc: Stephen Frost <sfrost@snowman.net>
Cc: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Cc: Matthias van de Meent <boekewurm+postgres@gmail.com>
Cc: Peter Smith <smithpb2250@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Tomas Vondra <tomas.vondra@enterprisedb.com>
Subject: Re: Statistics Import and Export
Date: Tue, 02 Apr 2024 18:18:53 -0400
Message-ID: <1846403.1712096333@sss.pgh.pa.us> (raw )
In-Reply-To: <06286ee47fa4b06b6e7f08da21958d7e35525ed4.camel@j-davis.com >
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Jeff Davis <pgsql@j-davis.com> writes:
> We need to get the original element type on the import side somehow,
> right? Otherwise it will be hard to tell whether '{1, 2, 3, 4}' has
> element type "int4" or "text", which affects the binary representation
> of the anyarray value in pg_statistic.
Yeah, but that problem exists no matter what. I haven't read enough
of the patch to find where it's determining that, but I assume there's
code in there to intuit the statistics storage type depending on the
table column's data type and the statistics kind.
> Either we need to get it at export time (which seems the most reliable
> in principle, but problematic for older versions) and pass it as an
> argument to pg_set_attribute_stats(); or we need to derive it reliably
> from the table schema on the destination side, right?
We could not trust the exporting side to tell us the correct answer;
for one reason, it might be different across different releases.
So "derive it reliably on the destination" is really the only option.
I think that it's impossible to do this in the general case, since
type-specific typanalyze functions can store pretty nearly whatever
they like. However, the pg_stats view isn't going to show nonstandard
statistics kinds anyway, so we are going to be lossy for custom
statistics kinds.
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, pgsql@j-davis.com, corey.huinker@gmail.com, magnus@hagander.net, sfrost@snowman.net, ashutosh.bapat.oss@gmail.com, boekewurm+postgres@gmail.com, smithpb2250@gmail.com, pgsql-hackers@lists.postgresql.org, tomas.vondra@enterprisedb.com
Subject: Re: Statistics Import and Export
In-Reply-To: <1846403.1712096333@sss.pgh.pa.us>
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