From: Ancoron Luciferis <ancoron.luciferis@googlemail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@lists.postgresql.org
Subject: Re: Custom opclass for column statistics?
Date: Wed, 10 Jul 2019 00:16:38 +0200
Message-ID: <ac9a8640-c421-7662-5e0c-05648c926176@googlemail.com> (raw)
In-Reply-To: <26689.1562421538@sss.pgh.pa.us>
References: <b0590dd1-5bfb-ad62-c4d0-a7057c04a68b@googlemail.com>
<26689.1562421538@sss.pgh.pa.us>
On 06/07/2019 15:58, Tom Lane wrote:
> Ancoron Luciferis <ancoron.luciferis@googlemail.com> writes:
>> I've been wondering whether it is possible somehow to have the standard
>> column statistics to respect a certain operator class?
>
> In principle, pg_statistic can represent stats for a non-default opclass.
> Teaching ANALYZE to collect such stats when appropriate, and then teaching
> the planner to use them when appropriate, is left as an exercise for the
> reader.
Hehe, now that you are saying it, I realize what I was actually asking
for with this... ;)
>
> I think the "when appropriate" bit is actually the hardest part of that.
> Possibly, if you were satisfied with a relatively manual approach,
> you could proceed by using CREATE STATISTICS to declare interest in
> keeping standard stats for a non-default sort order. Not sure what to
> do if you want it to be automatic, because I don't think people would
> hold still for having ANALYZE collect stats for any random non-default
> opclass automatically. Maybe a new opclass property?
I totally agree with the complications around all that.
Now I think if I want better statistics and better plans for my new
time-sorted index, I will need a new data type for which I can set the
opclass as default, which also would provide users the guarantee that
they'll get what they expect.
Thanx and cheers,
Ancoron
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Cc: ancoron.luciferis@googlemail.com, tgl@sss.pgh.pa.us, pgsql-performance@lists.postgresql.org
Subject: Re: Custom opclass for column statistics?
In-Reply-To: <ac9a8640-c421-7662-5e0c-05648c926176@googlemail.com>
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