2 files changed, 32 insertions, 0 deletions
diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index 8e6fc13bb38..a7b7b73ad6f 100644
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -2352,3 +2352,18 @@ execute foo(false);
  10000
 (1 row)
 
+--
+-- test for sane behavior with noncanonical merge clauses, per bug #4926
+--
+begin;
+set enable_mergejoin = 1;
+set enable_hashjoin = 0;
+set enable_nestloop = 0;
+create temp table a (i integer);
+create temp table b (x integer, y integer);
+select * from a left join b on i = x and i = y and x = i;
+ i | x | y 
+---+---+---
+(0 rows)
+
+rollback;
diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
index 149530e14db..29992ced0c2 100644
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -505,3 +505,20 @@ prepare foo(bool) as
         (select 1 from tenk1 c where c.thousand = b.unique2 and $1));
 execute foo(true);
 execute foo(false);
+
+--
+-- test for sane behavior with noncanonical merge clauses, per bug #4926
+--
+
+begin;
+
+set enable_mergejoin = 1;
+set enable_hashjoin = 0;
+set enable_nestloop = 0;
+
+create temp table a (i integer);
+create temp table b (x integer, y integer);
+
+select * from a left join b on i = x and i = y and x = i;
+
+rollback;