Horton

Re: POC, WIP: OR-clause support for indexes

Ranier Vilela <ranier.vf@gmail.com>

View thread
From: Ranier Vilela <ranier.vf@gmail.com>
To: Alena Rybakina <a.rybakina@postgrespro.ru>
Cc: Alexander Lakhin <exclusion@gmail.com>, Alexander Korotkov <aekorotkov@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>
Date: 2024-11-28T19:28:04Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Make group_similar_or_args() reorder clause list as little as possible

  2. Allow usage of match_orclause_to_indexcol() for joins

  3. Skip not SOAP-supported indexes while transforming an OR clause into SAOP

  4. Remove the wrong assertion from match_orclause_to_indexcol()

  5. Teach bitmap path generation about transforming OR-clauses to SAOP's

  6. Transform OR-clauses to SAOP's during index matching

  7. Fix the value of or_to_any_transform_limit in postgresql.conf.sample

  8. Transform OR clauses to ANY expression

  9. MergeAttributes code deduplication

  10. SEARCH and CYCLE clauses

  11. Improve estimation of OR clauses using extended statistics.

  12. Teach btree to handle ScalarArrayOpExpr quals natively.

  13. Revise collation derivation method and expression-tree representation.

  14. Instead of trying to force WHERE clauses into CNF or DNF normal form,

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;
+
  /*
  * 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)

best regards,
Ranier Vilela