MDEV-17576 Assertion in maria_extra upon ALTER on table with triggers and locks

The problem was that the code in maria_extra assumed that there could be
only one table open when doing maria_extra(MA_FORCE_REOPEN)
However in the case of triggers, there can be multiple copies of
the table open.

Fixed by removing assert.

mysql-test/suite/maria/alter.result

@@ -90,3 +90,17 @@ check table t2;
 Table	Op	Msg_type	Msg_text
 test.t2	check	status	OK
 DROP TABLE t1,t2;
+#
+# MDEV-17576
+# Assertion `share->reopen == 1' failed in maria_extra upon ALTER on
+# Aria table with triggers and locks
+#
+CREATE TABLE t1 (a INT) ENGINE=Aria;
+CREATE TRIGGER tr BEFORE INSERT ON t1 FOR EACH ROW INSERT INTO t1 SELECT * FROM t1;
+LOCK TABLE t1 WRITE;
+ALTER TABLE t1 FORCE, LOCK=EXCLUSIVE;
+DROP TRIGGER tr;
+DROP TABLE t1;
+#
+# End of 10.2 test
+#

mysql-test/suite/maria/alter.test

@@ -11,7 +11,7 @@ drop table if exists t1;
 CREATE TABLE t1 (pk INT, d DATETIME, PRIMARY KEY(pk), KEY(d)) ENGINE=Aria;
 ALTER TABLE t1 DISABLE KEYS;
 INSERT INTO t1 VALUES (1,'2000-01-01 22:22:22'),(2,'2012-12-21 12:12:12');
-INSERT INTO t1 VALUES (3, '2008-07-24'); 
+INSERT INTO t1 VALUES (3, '2008-07-24');
 ALTER TABLE t1 ENABLE KEYS;
 
 SELECT t1a.pk FROM t1 AS t1a LEFT JOIN t1 AS t1b ON t1a.pk = t1b.pk;
@@ -74,6 +74,19 @@ check table t1;
 check table t2;
 DROP TABLE t1,t2;
 
-#
-# End of 10.2 tests
-#
+--echo #
+--echo # MDEV-17576
+--echo # Assertion `share->reopen == 1' failed in maria_extra upon ALTER on
+--echo # Aria table with triggers and locks
+--echo #
+
+CREATE TABLE t1 (a INT) ENGINE=Aria;
+CREATE TRIGGER tr BEFORE INSERT ON t1 FOR EACH ROW INSERT INTO t1 SELECT * FROM t1;
+LOCK TABLE t1 WRITE;
+ALTER TABLE t1 FORCE, LOCK=EXCLUSIVE;
+DROP TRIGGER tr;
+DROP TABLE t1;
+
+--echo #
+--echo # End of 10.2 test
+--echo #

storage/maria/ma_extra.c

@@ -286,7 +286,6 @@ int maria_extra(MARIA_HA *info, enum ha_extra_function function,
       We however do a flush here for additional safety.
     */
     /** @todo consider porting these flush-es to MyISAM */
-    DBUG_ASSERT(share->reopen == 1);
     error= _ma_flush_table_files(info, MARIA_FLUSH_DATA | MARIA_FLUSH_INDEX,
                                  FLUSH_FORCE_WRITE, FLUSH_FORCE_WRITE);
     if (!error && share->changed)