Fix for bug #5890 "Triggers fail for DELETE without WHERE".

If we have DELETE with always true WHERE clause we should not use 
optimized delete_all_rows() method for tables with DELETE triggers,
because in this case we will lose side-effect of deletion.


mysql-test/r/trigger.result:
  Added test for bug #5890 "Triggers fail for DELETE without WHERE".
mysql-test/t/trigger.test:
  Added test for bug #5890 "Triggers fail for DELETE without WHERE".
sql/sql_delete.cc:
  mysql_delete(): 
    We should not use optimized delete_all_rows() method for tables
    with DELETE triggers, because in this case we will lose side-effect
    of deletion.
sql/sql_trigger.h:
  Added new Table_triggers_list::has_delete_triggers() method which
  allows to understand quickly if we have some DELETE triggers in
  our list.

mysql-test/r/trigger.result

@@ -174,3 +174,15 @@ create trigger tx1 before insert on t1 for each row set new.x1col = 'x';
 insert into t1 values ('y');
 drop trigger t1.tx1;
 drop table t1;
+create table t1 (i int) engine=myisam;
+insert into t1 values (1), (2);
+create trigger trg1 before delete on t1 for each row set @del_before:= @del_before + old.i;
+create trigger trg2 after delete on t1 for each row set @del_after:= @del_after + old.i;
+set @del_before:=0, @del_after:= 0;
+delete from t1;
+select @del_before, @del_after;
+@del_before	@del_after
+3	3
+drop trigger t1.trg1;
+drop trigger t1.trg2;
+drop table t1;

mysql-test/t/trigger.test

@@ -207,3 +207,20 @@ create trigger tx1 before insert on t1 for each row set new.x1col = 'x';
 insert into t1 values ('y');
 drop trigger t1.tx1;
 drop table t1;
+
+#
+# Test for bug #5890 "Triggers fail for DELETE without WHERE".
+# If we are going to delete all rows in table but DELETE triggers exist
+# we should perform row-by-row deletion instead of using optimized
+# delete_all_rows() method.
+#
+create table t1 (i int) engine=myisam;
+insert into t1 values (1), (2);
+create trigger trg1 before delete on t1 for each row set @del_before:= @del_before + old.i;
+create trigger trg2 after delete on t1 for each row set @del_after:= @del_after + old.i;
+set @del_before:=0, @del_after:= 0;
+delete from t1;
+select @del_before, @del_after;
+drop trigger t1.trg1;
+drop trigger t1.trg2;
+drop table t1;

sql/sql_delete.cc

@@ -62,9 +62,14 @@ int mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds, SQL_LIST *order,
   if (thd->lex->duplicates == DUP_IGNORE)
     thd->lex->select_lex.no_error= 1;
 
-  /* Test if the user wants to delete all rows */
+  /*
+    Test if the user wants to delete all rows and deletion doesn't have
+    any side-effects (because of triggers), so we can use optimized
+    handler::delete_all_rows() method.
+  */
   if (!using_limit && const_cond && (!conds || conds->val_int()) &&
-      !(specialflag & (SPECIAL_NO_NEW_FUNC | SPECIAL_SAFE_MODE)))
+      !(specialflag & (SPECIAL_NO_NEW_FUNC | SPECIAL_SAFE_MODE)) &&
+      !(table->triggers && table->triggers->has_delete_triggers()))
   {
     deleted= table->file->records;
     if (!(error=table->file->delete_all_rows()))

sql/sql_trigger.h

@@ -58,5 +58,11 @@ class Table_triggers_list: public Sql_alloc
   static bool check_n_load(THD *thd, const char *db, const char *table_name,
                            TABLE *table);
 
+  bool has_delete_triggers()
+  {
+    return (bodies[TRG_EVENT_DELETE][TRG_ACTION_BEFORE] ||
+            bodies[TRG_EVENT_DELETE][TRG_ACTION_AFTER]);
+  }
+
   friend class Item_trigger_field;
 };