Merge 10.3 into 10.4

1 files changed, 42 insertions, 0 deletions

diff --git a/mysql-test/main/key.result b/mysql-test/main/key.result
index 12f6c36edd8..3139caa9ae5 100644
--- a/mysql-test/main/key.result
+++ b/mysql-test/main/key.result
@@ -643,3 +643,45 @@ SHOW STATUS LIKE 'Last_query_cost';
 Variable_name	Value
 Last_query_cost	14.199000
 DROP TABLE t1;
+#
+# MDEV-21480: Unique key using ref access though eq_ref access can be used
+#
+create table t1(a int, b int,c int,  primary key(a), unique key(b,c));
+insert into t1 select seq, seq, seq from seq_1_to_10;
+create table t2(a int, b int,c int);
+insert into t2 select seq, seq, seq+1 from seq_1_to_100;
+EXPLAIN SELECT t1.c, t2.c FROM t1, t2 WHERE t1.b=t2.a and t1.c=t2.b;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	100	Using where
+1	SIMPLE	t1	eq_ref	b	b	10	test.t2.a,test.t2.b	1	Using index
+SELECT t1.c, t2.c FROM t1, t2 WHERE t1.b=t2.a and t1.c=t2.b;
+c	c
+1	2
+2	3
+3	4
+4	5
+5	6
+6	7
+7	8
+8	9
+9	10
+10	11
+alter table t1 drop PRIMARY KEY;
+alter table t1 add PRIMARY KEY(b,c);
+EXPLAIN SELECT t1.c, t2.c FROM t1, t2 WHERE t1.b=t2.a and t1.c=t2.b;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	100	Using where
+1	SIMPLE	t1	eq_ref	PRIMARY,b	PRIMARY	8	test.t2.a,test.t2.b	1	Using index
+SELECT t1.c, t2.c FROM t1, t2 WHERE t1.b=t2.a and t1.c=t2.b;
+c	c
+1	2
+2	3
+3	4
+4	5
+5	6
+6	7
+7	8
+8	9
+9	10
+10	11
+drop table t1,t2;