Bug #43867 ALTER TABLE on a partitioned table causes unnecessary

deadlocks

Backport of revno: 2617.68.35

The problem was that if one connection is running a multi-statement 
transaction which involves a single partitioned table, and another 
connection attempts to alter the table to drop a non-existing partition,
(which of course will fail), the first connection still gets 
ER_LOCK_DEADLOCK and cannot proceed anymore.

This bug is no longer reproducable. This has also been tested with the
patch for Bug#46654 "False deadlock on concurrent DML/DDL with partitions, 
inconsistent behavior" which concerned a similar problem but where the 
ALTER TABLE is semantically correct.

Test case added in partition_sync.test.

mysql-test/r/partition_sync.result

@@ -0,0 +1,25 @@
+#
+# Bug #43867 ALTER TABLE on a partitioned table 
+#            causes unnecessary deadlocks
+#
+CREATE TABLE t1 (a int) PARTITION BY RANGE (a)
+(PARTITION p0 VALUES LESS THAN (1),
+PARTITION p1 VALUES LESS THAN (2));
+INSERT INTO t1 VALUES (0),(1);
+# Connection 2
+BEGIN;
+SELECT * FROM t1;
+a
+0
+1
+# Connection 1
+ALTER TABLE t1 DROP PARTITION p3;
+ERROR HY000: Error in list of partitions to DROP
+# Connection 2
+# This failed with deadlock and should not do so.
+SELECT * FROM t1;
+a
+0
+1
+# Connection 1
+DROP TABLE t1;