Date: Wed, 2 Mar 2022 11:38:21 -0600
From: Justin Pryzby <pryzby@telsasoft.com>
To: Julien Rouhaud <rjuju123@gmail.com>
Cc: Andres Freund <andres@anarazel.de>,
	Tomas Vondra <tomas.vondra@enterprisedb.com>,
	pgsql-hackers@postgresql.org
Subject: Re: using extended statistics to improve join estimates
Message-ID: <20220302173821.GG15744@telsasoft.com>
References: <c8c0ff31-3a8a-7562-bbd3-78b2ec65f16c@enterprisedb.com>
 <2ed75657-e084-9539-c6de-597e5675014c@enterprisedb.com>
 <ff412e82-5427-3b72-cf32-4700156dc47c@enterprisedb.com>
 <20211122012315.GH17618@telsasoft.com>
 <0213d237-efd5-8e7e-fa29-3f36e6e26023@enterprisedb.com>
 <1ea3bf2b-57f9-e632-251a-e718623d7a72@enterprisedb.com>
 <20220104235550.dgr4rz6zkjx2rykz@alap3.anarazel.de>
 <20220119101809.wzrjvh4jsnoakgny@jrouhaud>
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On Wed, Jan 19, 2022 at 06:18:09PM +0800, Julien Rouhaud wrote:
> On Tue, Jan 04, 2022 at 03:55:50PM -0800, Andres Freund wrote:
> > On 2022-01-01 18:21:06 +0100, Tomas Vondra wrote:
> > > Here's an updated patch, rebased and fixing a couple typos reported by
> > > Justin Pryzby directly.
> > 
> > FWIW, cfbot reports a few compiler warnings:
> 
> Also the patch doesn't apply anymore:
> 
> http://cfbot.cputube.org/patch_36_3055.log
> === Applying patches on top of PostgreSQL commit ID 74527c3e022d3ace648340b79a6ddec3419f6732 ===
> === applying patch ./0001-Estimate-joins-using-extended-statistics-20220101.patch
> patching file src/backend/optimizer/path/clausesel.c
> patching file src/backend/statistics/extended_stats.c
> Hunk #1 FAILED at 30.
> Hunk #2 succeeded at 102 (offset 1 line).
> Hunk #3 succeeded at 2619 (offset 9 lines).
> 1 out of 3 hunks FAILED -- saving rejects to file src/backend/statistics/extended_stats.c.rej

Rebased over 269b532ae and muted compiler warnings.

Tomas - is this patch viable for pg15 , or should move to the next CF ?

In case it's useful, I ran this on cirrus with my branch for code coverage.
https://cirrus-ci.com/task/5816731397521408
https://api.cirrus-ci.com/v1/artifact/task/5816731397521408/coverage/coverage/00-index.html

statext_find_matching_mcv() has poor coverage.
statext_clauselist_join_selectivity() has poor coverage for the "stats2" case.

In mcv.c: mcv_combine_extended() and mcv_combine_simple() have poor coverage
for the "else if" cases (does it matter?)

Not related to this patch:
build_attnums_array() isn't being hit.

Same at statext_is_compatible_clause_internal()
    1538           0 :         *exprs = lappend(*exprs, clause);

statext_mcv_[de]serialize() aren't being hit for cstrings.

-- 
Justin