From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
cc: "David G. Johnston" <david.g.johnston@gmail.com>,
        =?utf-8?B?RmFicsOtemlv?= Mello <fabriziomello@gmail.com>,
        PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Add important info about ANALYZE after create Functional Index
In-reply-to: <20201028185538.fzux2lhim472h46o@development>
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Comments: In-reply-to Tomas Vondra <tomas.vondra@2ndquadrant.com>
	message dated "Wed, 28 Oct 2020 19:55:38 +0100"
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Date: Wed, 28 Oct 2020 15:05:39 -0400
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Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
> On Mon, Oct 26, 2020 at 03:46:10PM -0700, David G. Johnston wrote:
>> It would seem preferable to call the lack of auto-analyzing after these
>> operations a bug and back-patch a fix that injects an analyze side-effect
>> just before their completion.  It doesn't have to be smart either,
>> analyzing things even if the created (or newly validated) index doesn't
>> have statistics of its own isn't a problem in my book.

> I agree the lack of stats may be quite annoying and cause issues, but my
> guess is the chances of backpatching such change are about 0.000001%. We
> have a usable 'workaround' for this - manual analyze.

This doesn't seem clearly different from any other situation where
auto-analyze doesn't react fast enough to suit you.  I would not
call it a bug, at least not without a wholesale redefinition of
how auto-analyze is supposed to work.  As a close analogy, we
don't make any effort to force an immediate auto-analyze after
CREATE STATISTICS.

I don't see anything in the CREATE STATISTICS man page pointing
that out, either.  But there's probably room for "Notes" entries
about it in both places.

			regards, tom lane