Bug#22351 - handler::index_next_same() call to key_cmp_if_same() uses

            the wrong buffer
Post-pushbuild fix
Added test case for better coverage.

mysql-test/r/partition.result

@@ -289,6 +289,13 @@ select * from t1 where a = 4;
 a	b
 4	4
 drop table t1;
+CREATE TABLE t1 (c1 INT, c2 INT, PRIMARY KEY USING BTREE (c1,c2)) ENGINE=MEMORY
+PARTITION BY KEY(c2,c1) PARTITIONS 4;
+INSERT INTO t1 VALUES (0,0),(1,1),(2,2),(3,3),(4,4),(5,5),(6,6);
+SELECT * FROM t1 WHERE c1 = 4;
+c1	c2
+4	4
+DROP TABLE t1;
 CREATE TABLE t1 (a int)
 PARTITION BY LIST (a)
 PARTITIONS 1

mysql-test/t/partition.test

@@ -372,6 +372,16 @@ select * from t1 where a = 4;
 
 drop table t1;
 
+#
+# Bug#22351 - handler::index_next_same() call to key_cmp_if_same()
+#             uses the wrong buffer
+#
+CREATE TABLE t1 (c1 INT, c2 INT, PRIMARY KEY USING BTREE (c1,c2)) ENGINE=MEMORY
+  PARTITION BY KEY(c2,c1) PARTITIONS 4;
+INSERT INTO t1 VALUES (0,0),(1,1),(2,2),(3,3),(4,4),(5,5),(6,6);
+SELECT * FROM t1 WHERE c1 = 4;
+DROP TABLE t1;
+
 #
 # Bug #13438: Engine clause in PARTITION clause causes crash
 #