Bug#37548: result value erronously reported being NULL in certain subqueries

      
When switching to indexed ORDER BY we must be sure to reset the index read
flag if we are switching from a covering index to non-covering.

1 files changed, 44 insertions, 0 deletions

diff --git a/mysql-test/t/subselect.test b/mysql-test/t/subselect.test
index ee3a7428d4a..53257f32982 100644
--- a/mysql-test/t/subselect.test
+++ b/mysql-test/t/subselect.test
@@ -3273,3 +3273,47 @@ INSERT INTO t1 VALUES ('a');
 SELECT * FROM t1 WHERE _utf8'a' = ANY (SELECT s1 FROM t1);
 DROP TABLE t1;
 
+#
+# Bug #37548: result value erronously reported being NULL in certain subqueries
+#
+
+CREATE TABLE t1 (a int, b int, PRIMARY KEY (a), KEY b (b));
+
+INSERT INTO t1 VALUES (1,NULL), (9,NULL);
+
+CREATE TABLE t2 (
+  a int,
+  b int,
+  c int,
+  d int,
+  PRIMARY KEY (a),
+  UNIQUE KEY b (b,c,d),
+  KEY b_2 (b),
+  KEY c (c),
+  KEY d (d)
+);
+
+INSERT INTO t2 VALUES 
+  (43, 2, 11 ,30),
+  (44, 2, 12 ,30),
+  (45, 1, 1  ,10000),
+  (46, 1, 2  ,10000),
+  (556,1, 32 ,10000);
+
+CREATE TABLE t3 (
+  a int,
+  b int,
+  c int,
+  PRIMARY KEY (a),
+  UNIQUE KEY b (b,c),
+  KEY c (c),
+  KEY b_2 (b)
+);
+
+INSERT INTO t3 VALUES (1,1,1), (2,32,1);
+
+explain 
+SELECT t1.a, (SELECT 1 FROM t2 WHERE t2.b=t3.c AND t2.c=t1.a ORDER BY t2.d LIMIT 1) AS incorrect FROM t1, t3 WHERE t3.b=t1.a;
+SELECT t1.a, (SELECT 1 FROM t2 WHERE t2.b=t3.c AND t2.c=t1.a ORDER BY t2.d LIMIT 1) AS incorrect FROM t1, t3 WHERE t3.b=t1.a;
+
+DROP TABLE t1,t2,t3;