Now when we create or drop trigger we will open only subject table and not

all tables suggested by prelocking algorithm.
Added test for bug #11889 "Server crashes when dropping trigger using stored
routine" (which was fixed by previous patch).


mysql-test/r/trigger.result:
  Since we are using open_ltable() now to open table for trigger creation, code
  for error when we try to create trigger on view has changed to equivalent one.
  Added test for bug #11889 "Server crashes when dropping trigger using stored
  routine".
mysql-test/t/trigger.test:
  Since we are using open_ltable() now to open table for trigger creation, code
  for error when we try to create trigger on view has changed to equivalent one.
  Added test for bug #11889 "Server crashes when dropping trigger using stored
  routine".
sql/sql_trigger.cc:
  mysql_create_or_drop_trigger():
    It is better to open only table for which we are going to create or drop
    trigger with open_ltable() since we don't really need working prelocking
    in this case.

mysql-test/r/trigger.result

@@ -297,7 +297,7 @@ drop trigger t1.trg;
 ERROR HY000: Trigger does not exist
 create view v1 as select * from t1;
 create trigger trg before insert on v1 for each row set @a:=1;
-ERROR HY000: Trigger's 'v1' is view or temporary table
+ERROR HY000: 'test.v1' is not BASE TABLE
 drop view v1;
 drop table t1;
 create temporary table t1 (i int);
@@ -578,4 +578,5 @@ create trigger t1_bu before update on t1 for each row set new.col1= bug5893();
 drop function bug5893;
 update t1 set col2 = 4;
 ERROR 42000: FUNCTION test.bug5893 does not exist
+drop trigger t1.t1_bu;
 drop table t1;

mysql-test/t/trigger.test

@@ -317,7 +317,7 @@ drop trigger t1.trg;
 drop trigger t1.trg;
 
 create view v1 as select * from t1;
---error 1361
+--error 1347
 create trigger trg before insert on v1 for each row set @a:=1;
 drop view v1;
 
@@ -576,6 +576,8 @@ drop table t1, t2;
 
 # Test for bug #5893 "Triggers with dropped functions cause crashes"
 # Appropriate error should be reported instead of crash.
+# Also test for bug #11889 "Server crashes when dropping trigger
+# using stored routine".
 --disable_warnings
 drop function if exists bug5893;
 --enable_warnings
@@ -586,4 +588,6 @@ create trigger t1_bu before update on t1 for each row set new.col1= bug5893();
 drop function bug5893; 
 --error 1305
 update t1 set col2 = 4;
+# This should not crash server too.
+drop trigger t1.t1_bu;
 drop table t1;

sql/sql_trigger.cc

@@ -69,7 +69,10 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
     But do we want this ?
   */
 
-  if (open_and_lock_tables(thd, tables))
+  /* We should have only one table in table list. */
+  DBUG_ASSERT(tables->next_global == 0);
+
+  if (!(table= open_ltable(thd, tables, tables->lock_type)))
     DBUG_RETURN(TRUE);
 
   /*
@@ -80,8 +83,6 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
   if (check_global_access(thd, SUPER_ACL))
     DBUG_RETURN(TRUE);
 
-  table= tables->table;
-
   /*
     We do not allow creation of triggers on views or temporary tables.
     We have to do this check here and not in