Merge 10.5 into 10.6

mysql-test/suite/innodb/r/cursor-restore-unique-null.result

@@ -0,0 +1,24 @@
+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";
+SELECT * FROM t FORCE INDEX(b) FOR UPDATE;
+connection con1;
+SET DEBUG_SYNC="now WAIT_FOR select_locked";
+ROLLBACK;
+connection default;
+# If the bug is not fixed, and the both unique index key fields are
+# NULL, there will be two (1, NULL, 2) rows in the result,
+# because cursor will be restored to (NULL, 2, 1) position for
+# secondary key instead of "supremum".
+a	b	c
+1	NULL	2
+COMMIT;
+SET DEBUG_SYNC="RESET";
+disconnect con1;
+DROP TABLE t;