Re: POC, WIP: OR-clause support for indexes - Mailing list pgsql-hackers

On Fri, Nov 29, 2024 at 7:51 AM Alena Rybakina
<a.rybakina@postgrespro.ru> wrote:
>
> On 29.11.2024 03:04, Alexander Korotkov wrote:
> > On Thu, Nov 28, 2024 at 9:33 PM Alena Rybakina
> > <a.rybakina@postgrespro.ru> wrote:
> >> On 28.11.2024 22:28, Ranier Vilela wrote:
> >>
> >> Em qui., 28 de nov. de 2024 às 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 = 1;
> >>>> CREATE TABLE tbl(u UUID);
> >>>> CREATE INDEX idx ON tbl USING HASH (u);
> >>>> SELECT COUNT(*) FROM tbl WHERE u = '00000000000000000000000000000000' OR
> >>>>    u = '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 useless?
> >> Maybe moving your fix to the beginning of the function?
> >>
> >> diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/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 == 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 (constant
> >>
> >> The test bug:
> >> EXPLAIN SELECT COUNT(*) FROM tbl WHERE u = '00000000000000000000000000000000' OR u =
'11111111111111111111111111111111';
> >>                                                              QUERY PLAN
> >>
----------------------------------------------------------------------------------------------------------------------------------
> >>   Aggregate  (cost=12.46..12.47 rows=1 width=8)
> >>     ->  Bitmap Heap Scan on tbl  (cost=2.14..12.41 rows=18 width=0)
> >>           Recheck Cond: ((u = '00000000-0000-0000-0000-000000000000'::uuid) OR (u =
'11111111-1111-1111-1111-111111111111'::uuid))
> >>           ->  BitmapOr  (cost=2.14..2.14 rows=18 width=0)
> >>                 ->  Bitmap Index Scan on idx  (cost=0.00..1.07 rows=9 width=0)
> >>                       Index Cond: (u = '00000000-0000-0000-0000-000000000000'::uuid)
> >>                 ->  Bitmap Index Scan on idx  (cost=0.00..1.07 rows=9 width=0)
> >>                       Index Cond: (u = '11111111-1111-1111-1111-111111111111'::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