From: Peter Eisentraut <peter@eisentraut.org>
Date: Mon, 15 Sep 2025 14:27:50 +0000 (+0200)
Subject: Expand virtual generated columns in constraint expressions
X-Git-Tag: REL_18_0~29
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=e7a2bbdb522dd6fc7283550742b8b52605198783;p=thirdparty%2Fpostgresql.git

Expand virtual generated columns in constraint expressions

Virtual generated columns in constraint expressions need to be
expanded because the optimizer matches these expressions to qual
clauses.  Failing to do so can cause us to miss opportunities for
constraint exclusion.

Author: Richard Guo <guofenglinux@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/204804c0-798f-4c72-bd1f-36116024fda3%40eisentraut.org
---

diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index 95671771c79..6d420bb427f 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -42,6 +42,7 @@
 #include "parser/parse_relation.h"
 #include "parser/parsetree.h"
 #include "partitioning/partdesc.h"
+#include "rewrite/rewriteHandler.h"
 #include "rewrite/rewriteManip.h"
 #include "statistics/statistics.h"
 #include "storage/bufmgr.h"
@@ -1392,6 +1393,14 @@ get_relation_constraints(PlannerInfo *root,
 		result = list_concat(result, rel->partition_qual);
 	}
 
+	/*
+	 * Expand virtual generated columns in the constraint expressions.
+	 */
+	if (result)
+		result = (List *) expand_generated_columns_in_expr((Node *) result,
+														   relation,
+														   varno);
+
 	table_close(relation, NoLock);
 
 	return result;
diff --git a/src/test/regress/expected/generated_virtual.out b/src/test/regress/expected/generated_virtual.out
index 3b40e15a95a..e076977e986 100644
--- a/src/test/regress/expected/generated_virtual.out
+++ b/src/test/regress/expected/generated_virtual.out
@@ -1614,3 +1614,26 @@ select * from gtest32 t group by grouping sets (a, b, c, d, e) having c = 20;
 -- Ensure that the virtual generated columns in ALTER COLUMN TYPE USING expression are expanded
 alter table gtest32 alter column e type bigint using b;
 drop table gtest32;
+-- Ensure that virtual generated columns in constraint expressions are expanded
+create table gtest33 (a int, b int generated always as (a * 2) virtual not null, check (b > 10));
+set constraint_exclusion to on;
+-- should get a dummy Result, not a seq scan
+explain (costs off)
+select * from gtest33 where b < 10;
+        QUERY PLAN        
+--------------------------
+ Result
+   One-Time Filter: false
+(2 rows)
+
+-- should get a dummy Result, not a seq scan
+explain (costs off)
+select * from gtest33 where b is null;
+        QUERY PLAN        
+--------------------------
+ Result
+   One-Time Filter: false
+(2 rows)
+
+reset constraint_exclusion;
+drop table gtest33;
diff --git a/src/test/regress/sql/generated_virtual.sql b/src/test/regress/sql/generated_virtual.sql
index e2b31853e01..63be8edb249 100644
--- a/src/test/regress/sql/generated_virtual.sql
+++ b/src/test/regress/sql/generated_virtual.sql
@@ -859,3 +859,18 @@ select * from gtest32 t group by grouping sets (a, b, c, d, e) having c = 20;
 alter table gtest32 alter column e type bigint using b;
 
 drop table gtest32;
+
+-- Ensure that virtual generated columns in constraint expressions are expanded
+create table gtest33 (a int, b int generated always as (a * 2) virtual not null, check (b > 10));
+set constraint_exclusion to on;
+
+-- should get a dummy Result, not a seq scan
+explain (costs off)
+select * from gtest33 where b < 10;
+
+-- should get a dummy Result, not a seq scan
+explain (costs off)
+select * from gtest33 where b is null;
+
+reset constraint_exclusion;
+drop table gtest33;