Fix for bug #46614: Assertion in show_create_trigger()

on SHOW CREATE TRIGGER + MERGE table

Problem: SHOW CREATE TRIGGER erroneously relies on fact
that we have the only underlying table for a trigger
(wrong for merge tables).

Fix: remove erroneous assert().

mysql-test/r/merge.result

@@ -2207,4 +2207,16 @@ ERROR HY000: Table storage engine for 'm1' doesn't have this option
 DROP TABLE m1,t1,t2,t3,t4,t5,t6,t7;
 SELECT 1 FROM m1;
 ERROR 42S02: Table 'test.m1' doesn't exist
+#
+# Bug #46614: Assertion in show_create_trigger()
+#
+CREATE TABLE t1(a int);
+CREATE TABLE t2(a int);
+CREATE TABLE t3(a int) ENGINE = MERGE UNION(t1, t2);
+CREATE TRIGGER tr1 AFTER INSERT ON t3 FOR EACH ROW CALL foo();
+SHOW CREATE TRIGGER tr1;
+Trigger	sql_mode	SQL Original Statement	character_set_client	collation_connection	Database Collation
+tr1		CREATE DEFINER=`root`@`localhost` TRIGGER tr1 AFTER INSERT ON t3 FOR EACH ROW CALL foo()	latin1	latin1_swedish_ci	latin1_swedish_ci
+DROP TRIGGER tr1;
+DROP TABLE t1, t2, t3;
 End of 5.1 tests

mysql-test/t/merge.test

@@ -1622,4 +1622,15 @@ DROP TABLE m1,t1,t2,t3,t4,t5,t6,t7;
 --error ER_NO_SUCH_TABLE
 SELECT 1 FROM m1; # Should not hang!
 
+--echo #
+--echo # Bug #46614: Assertion in show_create_trigger()
+--echo #
+CREATE TABLE t1(a int);
+CREATE TABLE t2(a int);
+CREATE TABLE t3(a int) ENGINE = MERGE UNION(t1, t2);
+CREATE TRIGGER tr1 AFTER INSERT ON t3 FOR EACH ROW CALL foo();
+SHOW CREATE TRIGGER tr1;
+DROP TRIGGER tr1;
+DROP TABLE t1, t2, t3;
+
 --echo End of 5.1 tests

sql/sql_show.cc

@@ -7071,8 +7071,6 @@ bool show_create_trigger(THD *thd, const sp_name *trg_name)
     /* Perform closing actions and return error status. */
   }
 
-  DBUG_ASSERT(num_tables == 1);
-
   Table_triggers_list *triggers= lst->table->triggers;
 
   if (!triggers)