Merge fix for bug#17711

mysql-test/r/delete.result

@@ -186,4 +186,11 @@ select count(*) from t1;
 count(*)
 0
 drop table t1;
+create table t1(f1 int primary key);
+insert into t1 values (4),(3),(1),(2);
+delete from t1 where (@a:= f1) order by f1 limit 1;
+select @a;
+@a
+1
+drop table t1;
 End of 4.1 tests

mysql-test/t/delete.test

@@ -174,4 +174,14 @@ delete from t1 where a is null;
 select count(*) from t1; 
 drop table t1; 
 
+#
+# Bug#17711: DELETE doesn't use index when ORDER BY, LIMIT and
+#            non-restricting WHERE is present.
+#
+create table t1(f1 int primary key);
+insert into t1 values (4),(3),(1),(2);
+delete from t1 where (@a:= f1) order by f1 limit 1;
+select @a;
+drop table t1;
+
 --echo End of 4.1 tests

sql/sql_delete.cc

@@ -142,7 +142,7 @@ int mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
       DBUG_RETURN(-1);			// This will force out message
     }
     
-    if (!select && limit != HA_POS_ERROR)
+    if ((!select || table->quick_keys.is_clear_all()) && limit != HA_POS_ERROR)
       usable_index= get_index_for_order(table, (ORDER*)(order->first), limit);
 
     if (usable_index == MAX_KEY)