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In-Reply-To: <43db6a40-5c5f-4909-ad62-3060b297e686@postgrespro.ru>
From: Alexander Korotkov <aekorotkov@gmail.com>
Date: Fri, 29 Nov 2024 09:54:02 +0200
Message-ID: <CAPpHfdtgcye9ELaLHw4ZOUxWQ9t1P=oBDJX8KwwOHqasESdXQQ@mail.gmail.com>
Subject: Re: POC, WIP: OR-clause support for indexes
To: Alena Rybakina <a.rybakina@postgrespro.ru>
Cc: Ranier Vilela <ranier.vf@gmail.com>, Alexander Lakhin <exclusion@gmail.com>, 
	Andrei Lepikhov <lepihov@gmail.com>, jian he <jian.universality@gmail.com>, 
	Robert Haas <robertmhaas@gmail.com>, Nikolay Shaplov <dhyan@nataraj.su>, 
	pgsql-hackers@lists.postgresql.org, pgsql-hackers@postgresql.org, 
	Peter Geoghegan <pg@bowt.ie>, Marcos Pegoraro <marcos@f10.com.br>, teodor@sigaev.ru, 
	Peter Eisentraut <peter@eisentraut.org>
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On Fri, Nov 29, 2024 at 7:51=E2=80=AFAM Alena Rybakina
<a.rybakina@postgrespro.ru> wrote:
>
> On 29.11.2024 03:04, Alexander Korotkov wrote:
> > On Thu, Nov 28, 2024 at 9:33=E2=80=AFPM Alena Rybakina
> > <a.rybakina@postgrespro.ru> wrote:
> >> On 28.11.2024 22:28, Ranier Vilela wrote:
> >>
> >> Em qui., 28 de nov. de 2024 =C3=A0s 16:03, Alena Rybakina <a.rybakina@=
postgrespro.ru> escreveu:
> >>> Hi! Thank you for the case.
> >>>
> >>> On 28.11.2024 21:00, Alexander Lakhin wrote:
> >>>> Hello Alexander,
> >>>>
> >>>> 21.11.2024 09:34, Alexander Korotkov wrote:
> >>>>> I'm going to push this if no objections.
> >>>> Please look at the following query, which triggers an error after
> >>>> ae4569161:
> >>>> SET random_page_cost =3D 1;
> >>>> CREATE TABLE tbl(u UUID);
> >>>> CREATE INDEX idx ON tbl USING HASH (u);
> >>>> SELECT COUNT(*) FROM tbl WHERE u =3D '000000000000000000000000000000=
00' OR
> >>>>    u =3D '11111111111111111111111111111111';
> >>>>
> >>>> ERROR:  XX000: ScalarArrayOpExpr index qual found where not allowed
> >>>> LOCATION:  ExecIndexBuildScanKeys, nodeIndexscan.c:1625
> >>>>
> >>>>
> >>> I found out what the problem is index scan method was not generated. =
We
> >>> need to check this during OR clauses for SAOP transformation.
> >>>
> >>> There is a patch to fix this problem.
> >> Hi.
> >> Thanks for the quick fix.
> >>
> >> But I wonder if it is not possible to avoid all if the index is useles=
s?
> >> Maybe moving your fix to the beginning of the function?
> >>
> >> diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optim=
izer/path/indxpath.c
> >> index d827fc9f4d..5ea0b27d01 100644
> >> --- a/src/backend/optimizer/path/indxpath.c
> >> +++ b/src/backend/optimizer/path/indxpath.c
> >> @@ -3248,6 +3248,10 @@ match_orclause_to_indexcol(PlannerInfo *root,
> >>    Assert(IsA(orclause, BoolExpr));
> >>    Assert(orclause->boolop =3D=3D OR_EXPR);
> >>
> >> + /* Ignore index if it doesn't support index scans */
> >> + if(!index->amsearcharray)
> >> + return NULL;
> >> +
> >>
> >> Agree. I have updated the patch
> >>
> >>    /*
> >>    * Try to convert a list of OR-clauses to a single SAOP expression. =
Each
> >>    * OR entry must be in the form: (indexkey operator constant) or (co=
nstant
> >>
> >> The test bug:
> >> EXPLAIN SELECT COUNT(*) FROM tbl WHERE u =3D '000000000000000000000000=
00000000' OR u =3D '11111111111111111111111111111111';
> >>                                                              QUERY PLA=
N
> >> ----------------------------------------------------------------------=
------------------------------------------------------------
> >>   Aggregate  (cost=3D12.46..12.47 rows=3D1 width=3D8)
> >>     ->  Bitmap Heap Scan on tbl  (cost=3D2.14..12.41 rows=3D18 width=
=3D0)
> >>           Recheck Cond: ((u =3D '00000000-0000-0000-0000-000000000000'=
::uuid) OR (u =3D '11111111-1111-1111-1111-111111111111'::uuid))
> >>           ->  BitmapOr  (cost=3D2.14..2.14 rows=3D18 width=3D0)
> >>                 ->  Bitmap Index Scan on idx  (cost=3D0.00..1.07 rows=
=3D9 width=3D0)
> >>                       Index Cond: (u =3D '00000000-0000-0000-0000-0000=
00000000'::uuid)
> >>                 ->  Bitmap Index Scan on idx  (cost=3D0.00..1.07 rows=
=3D9 width=3D0)
> >>                       Index Cond: (u =3D '11111111-1111-1111-1111-1111=
11111111'::uuid)
> >> (8 rows)
> > I slightly revised the fix and added similar check to
> > group_similar_or_args().  Could you, please, review that before
> > commit?
> >
> I agree with changes. Thank you!

Andrei, Alena, thank you for the feedback. Pushed!

------
Regards,
Alexander Korotkov
Supabase