Subject: Re: query of partitioned object doesnt use index in qa
To: Tom Lane <tgl@sss.pgh.pa.us>, Andres Freund <andres@anarazel.de>
Cc: pgsql-performance@postgresql.org, Mike Broers <mbroers@gmail.com>,
 David Rowley <david.rowley@2ndquadrant.com>
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 <862584A2-724B-4F5A-976F-6164AE61BBE5@anarazel.de>
 <9414.1505513131@sss.pgh.pa.us>
From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Message-ID: <a9e927d0-f908-05bf-83ba-fd252d6bdedb@2ndquadrant.com>
Date: Sat, 16 Sep 2017 00:26:06 +0200
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On 09/16/2017 12:05 AM, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
>> I'm wondering if we should extend the new CREATE STATISTICS
>> framework to be able to do that without requiring an index.
> 
> I think that's already on the roadmap --- it's one of the reasons we 
> ended up with a SELECT-like syntax for CREATE STATISTICS. But it 
> didn't get done for v10.
> 

Right. It's one of the things I'd like to be working on after getting in
the more complex statistics types (MCV & histograms).

> If we do look at that as a substitute for "make an expression index
> just so you get some stats", it would be good to have a way to
> specify that you only want the standard ANALYZE stats on that value
> and not the extended ones.
> 

Not sure I understand what you mean by "extended" - the statistics we
collect for expression indexes, or the CREATE STATISTICS stuff? I assume
the former, because if you don't want the latter then just don't create
the statistics. Or am I missing something?

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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