[David Geier <geidav.pg@gmail.com>]

Hi hackers,

The hashed IN optimization is only applied to the first encountered 
ScalarArrayOpExpr during the expression tree traversal in 
convert_saop_to_hashed_saop_walker(). Reason being that the walker 
returns true which aborts the traversal.

This can be exhibited by running a query with two IN statements vs the 
same query with just a single IN statement. The IN statements are 
combined via OR and both statements return no rows to prevent any kind 
of lazy evaluation optimizations. The query with two IN statements is 6x 
slower than the the query with the single IN statement. See the attached 
example.

I've also attached a patch with a fix.

-- 
David Geier
(ServiceNow)
CREATE TABLE test (col TEXT);
INSERT INTO test select 'testtesttest' FROM generate_series(1, 10000000);
\timing on

SELECT * FROM
  test
WHERE
  col IN ('testtesttesttesa', 'testtesttesttesb', 'testtesttesttesc', 'testtesttesttesd', 'testtesttesttese', 'testtesttesttesf', 'testtesttesttesg', 'testtesttesttesh', 'testtesttesttesi', 'testtesttesttesj', 'testtesttesttesk', 'testtesttesttesl', 'testtesttesttesm', 'testtesttesttesn', 'testtesttestteso', 'testtesttesttesp', 'testtesttesttesq', 'testtesttesttesr', 'testtesttesttess', 'testtesttesttes-', 'testtesttesttesu', 'testtesttesttesv', 'testtesttesttesw', 'testtesttesttesx', 'testtesttesttesy', 'testtesttesttesz', 'testtesttesttes1', 'testtesttesttes2', 'testtesttesttes3', 'testtesttesttes4', 'testtesttesttes5', 'testtesttesttes6', 'testtesttesttes7', 'testtesttesttes8', 'testtesttesttes9', 'testtesttesttes0');

SELECT * FROM
  test
WHERE
  col IN ('testtesttesttesa', 'testtesttesttesb', 'testtesttesttesc', 'testtesttesttesd', 'testtesttesttese', 'testtesttesttesf', 'testtesttesttesg', 'testtesttesttesh', 'testtesttesttesi', 'testtesttesttesj', 'testtesttesttesk', 'testtesttesttesl', 'testtesttesttesm', 'testtesttesttesn', 'testtesttestteso', 'testtesttesttesp', 'testtesttesttesq', 'testtesttesttesr', 'testtesttesttess', 'testtesttesttes-', 'testtesttesttesu', 'testtesttesttesv', 'testtesttesttesw', 'testtesttesttesx', 'testtesttesttesy', 'testtesttesttesz', 'testtesttesttes1', 'testtesttesttes2', 'testtesttesttes3', 'testtesttesttes4', 'testtesttesttes5', 'testtesttesttes6', 'testtesttesttes7', 'testtesttesttes8', 'testtesttesttes9', 'testtesttesttes0')
  OR
  col IN ('testtesttesttesa2', 'testtesttesttesb', 'testtesttesttesc', 'testtesttesttesd', 'testtesttesttese', 'testtesttesttesf', 'testtesttesttesg', 'testtesttesttesh', 'testtesttesttesi', 'testtesttesttesj', 'testtesttesttesk', 'testtesttesttesl', 'testtesttesttesm', 'testtesttesttesn', 'testtesttestteso', 'testtesttesttesp', 'testtesttesttesq', 'testtesttesttesr', 'testtesttesttess', 'testtesttesttes-', 'testtesttesttesu', 'testtesttesttesv', 'testtesttesttesw', 'testtesttesttesx', 'testtesttesttesy', 'testtesttesttesz', 'testtesttesttes1', 'testtesttesttes2', 'testtesttesttes3', 'testtesttesttes4', 'testtesttesttes5', 'testtesttesttes6', 'testtesttesttes7', 'testtesttesttes8', 'testtesttesttes9', 'testtesttesttes0');
From 7de592928acada597f6e4314036abd87a6af6403 Mon Sep 17 00:00:00 2001
From: David Geier <geidav.pg@gmail.com>
Date: Tue, 1 Apr 2025 13:47:27 +0200
Subject: [PATCH] Fixed hashed SAOP

---
 src/backend/optimizer/util/clauses.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 43dfecfb47f..05d33461163 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2326,7 +2326,7 @@ convert_saop_to_hashed_saop_walker(Node *node, void *context)
 						/* Looks good. Fill in the hash functions */
 						saop->hashfuncid = lefthashfunc;
 					}
-					return true;
+					return false;
 				}
 			}
 			else				/* !saop->useOr */
@@ -2364,7 +2364,7 @@ convert_saop_to_hashed_saop_walker(Node *node, void *context)
 						 */
 						saop->negfuncid = get_opcode(negator);
 					}
-					return true;
+					return false;
 				}
 			}
 		}
-- 
2.34.1



Attachments:

  [text/plain] example.sql (2.3K, ../29a76f51-97b0-4c07-87b7-ec8e3b5345c9@gmail.com/2-example.sql)
  download | inline:
CREATE TABLE test (col TEXT);
INSERT INTO test select 'testtesttest' FROM generate_series(1, 10000000);
\timing on

SELECT * FROM
  test
WHERE
  col IN ('testtesttesttesa', 'testtesttesttesb', 'testtesttesttesc', 'testtesttesttesd', 'testtesttesttese', 'testtesttesttesf', 'testtesttesttesg', 'testtesttesttesh', 'testtesttesttesi', 'testtesttesttesj', 'testtesttesttesk', 'testtesttesttesl', 'testtesttesttesm', 'testtesttesttesn', 'testtesttestteso', 'testtesttesttesp', 'testtesttesttesq', 'testtesttesttesr', 'testtesttesttess', 'testtesttesttes-', 'testtesttesttesu', 'testtesttesttesv', 'testtesttesttesw', 'testtesttesttesx', 'testtesttesttesy', 'testtesttesttesz', 'testtesttesttes1', 'testtesttesttes2', 'testtesttesttes3', 'testtesttesttes4', 'testtesttesttes5', 'testtesttesttes6', 'testtesttesttes7', 'testtesttesttes8', 'testtesttesttes9', 'testtesttesttes0');

SELECT * FROM
  test
WHERE
  col IN ('testtesttesttesa', 'testtesttesttesb', 'testtesttesttesc', 'testtesttesttesd', 'testtesttesttese', 'testtesttesttesf', 'testtesttesttesg', 'testtesttesttesh', 'testtesttesttesi', 'testtesttesttesj', 'testtesttesttesk', 'testtesttesttesl', 'testtesttesttesm', 'testtesttesttesn', 'testtesttestteso', 'testtesttesttesp', 'testtesttesttesq', 'testtesttesttesr', 'testtesttesttess', 'testtesttesttes-', 'testtesttesttesu', 'testtesttesttesv', 'testtesttesttesw', 'testtesttesttesx', 'testtesttesttesy', 'testtesttesttesz', 'testtesttesttes1', 'testtesttesttes2', 'testtesttesttes3', 'testtesttesttes4', 'testtesttesttes5', 'testtesttesttes6', 'testtesttesttes7', 'testtesttesttes8', 'testtesttesttes9', 'testtesttesttes0')
  OR
  col IN ('testtesttesttesa2', 'testtesttesttesb', 'testtesttesttesc', 'testtesttesttesd', 'testtesttesttese', 'testtesttesttesf', 'testtesttesttesg', 'testtesttesttesh', 'testtesttesttesi', 'testtesttesttesj', 'testtesttesttesk', 'testtesttesttesl', 'testtesttesttesm', 'testtesttesttesn', 'testtesttestteso', 'testtesttesttesp', 'testtesttesttesq', 'testtesttesttesr', 'testtesttesttess', 'testtesttesttes-', 'testtesttesttesu', 'testtesttesttesv', 'testtesttesttesw', 'testtesttesttesx', 'testtesttesttesy', 'testtesttesttesz', 'testtesttesttes1', 'testtesttesttes2', 'testtesttesttes3', 'testtesttesttes4', 'testtesttesttes5', 'testtesttesttes6', 'testtesttesttes7', 'testtesttesttes8', 'testtesttesttes9', 'testtesttesttes0');

  [text/plain] 0001-Fixed-hashed-SAOP.patch (983B, ../29a76f51-97b0-4c07-87b7-ec8e3b5345c9@gmail.com/3-0001-Fixed-hashed-SAOP.patch)
  download | inline diff:
From 7de592928acada597f6e4314036abd87a6af6403 Mon Sep 17 00:00:00 2001
From: David Geier <geidav.pg@gmail.com>
Date: Tue, 1 Apr 2025 13:47:27 +0200
Subject: [PATCH] Fixed hashed SAOP

---
 src/backend/optimizer/util/clauses.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 43dfecfb47f..05d33461163 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2326,7 +2326,7 @@ convert_saop_to_hashed_saop_walker(Node *node, void *context)
 						/* Looks good. Fill in the hash functions */
 						saop->hashfuncid = lefthashfunc;
 					}
-					return true;
+					return false;
 				}
 			}
 			else				/* !saop->useOr */
@@ -2364,7 +2364,7 @@ convert_saop_to_hashed_saop_walker(Node *node, void *context)
 						 */
 						saop->negfuncid = get_opcode(negator);
 					}
-					return true;
+					return false;
 				}
 			}
 		}
-- 
2.34.1