Fixed bug mdev-4996.

The fix for bug mdev-4971 not always correctly set the pointers to
inherited multiple equalities in objects of the Item_equal class. 

1 files changed, 23 insertions, 0 deletions

diff --git a/mysql-test/t/subselect2.test b/mysql-test/t/subselect2.test
index 75cf842fbdb..5d39499d36b 100644
--- a/mysql-test/t/subselect2.test
+++ b/mysql-test/t/subselect2.test
@@ -222,5 +222,28 @@ SELECT * FROM t3
               GROUP BY t1.b);
 DROP TABLE t1, t2, t3;
 
+--echo #
+--echo # MDEV-4996: degenerate OR formula in WHERE of a subquery
+--echo #
+
+CREATE TABLE t1 (a int, c1 varchar(1)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (2,'x'), (8,'d');
+
+CREATE TABLE t2 (m int, n int, c2 varchar(1)) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (0, 5, 'x'), (1, 4,'p');
+
+SELECT * FROM t1 WHERE c1 NOT IN ( 
+  SELECT t2a.c2 FROM t2 AS t2a, t2 AS t2b, t2 AS t2c 
+    WHERE t2c.c2 = t2b.c2 AND ( t2a.m = t2b.n OR 0 ) AND
+            ( t2b.m != a OR t2b.m = t2a.m ));
+
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE c1 NOT IN ( 
+  SELECT t2a.c2 FROM t2 AS t2a, t2 AS t2b, t2 AS t2c 
+    WHERE t2c.c2 = t2b.c2 AND ( t2a.m = t2b.n OR 0 ) AND
+            ( t2b.m != a OR t2b.m = t2a.m ));
+
+DROP TABLE t1,t2;
+
 set optimizer_switch=@subselect2_test_tmp;