Merge 10.5 into 10.6

mysql-test/suite/innodb/t/cursor-restore-unique-null.test

@@ -0,0 +1,36 @@
+--source include/have_innodb.inc
+--source include/have_debug.inc
+--source include/have_debug_sync.inc
+--source include/count_sessions.inc
+
+
+CREATE TABLE t(a INT PRIMARY KEY, b INT, c INT, UNIQUE KEY `b_c` (`b`,`c`))
+  ENGINE=InnoDB, STATS_PERSISTENT=0;
+INSERT INTO t SET a = 1, c = 2;
+
+--connect con1,localhost,root
+BEGIN;
+  INSERT INTO t SET a=2, c=2;
+
+--connection default
+BEGIN;
+SET DEBUG_SYNC="lock_wait_start SIGNAL select_locked";
+--send SELECT * FROM t FORCE INDEX(b) FOR UPDATE
+
+--connection con1
+SET DEBUG_SYNC="now WAIT_FOR select_locked";
+ROLLBACK;
+
+--connection default
+--echo # If the bug is not fixed, and the both unique index key fields are
+--echo # NULL, there will be two (1, NULL, 2) rows in the result,
+--echo # because cursor will be restored to (NULL, 2, 1) position for
+--echo # secondary key instead of "supremum".
+--reap
+COMMIT;
+
+SET DEBUG_SYNC="RESET";
+
+--disconnect con1
+DROP TABLE t;
+--source include/wait_until_count_sessions.inc