Bug #35206: select query result different if the key is indexed or not

The code for executing indexed ORDER BY was not setting all the 
internal fields correctly when selecting to execute ORDER BY over
and index.
Fixed by change the access method to one that will use the 
quick indexed access if one is selected while selecting indexed
ORDER BY.

mysql-test/r/order_by.result

@@ -1428,3 +1428,33 @@ set session max_sort_length= 2180;
 select * from t1 order by b;
 ERROR HY001: Out of sort memory; increase server sort buffer size
 drop table t1;
+CREATE TABLE t2 (a varchar(32), b int(11), c float, d double, 
+UNIQUE KEY a (a,b,c), KEY b (b), KEY c (c));
+CREATE TABLE t1 (a varchar(32), b char(3), UNIQUE KEY a (a,b), KEY b (b));
+CREATE TABLE t3 (a varchar(32), b char(3), UNIQUE KEY a (a,b));
+INSERT INTO t3 SELECT * FROM t1;
+EXPLAIN
+SELECT d FROM t1, t2
+WHERE t2.b=14 AND t2.a=t1.a AND 5.1<t2.c AND t1.b='DE'
+ORDER BY t2.c LIMIT 1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	a,b	b	4	const	4	Using where; Using temporary; Using filesort
+1	SIMPLE	t2	ref	a,b,c	a	40	test.t1.a,const	11	Using where
+SELECT d FROM t1, t2
+WHERE t2.b=14 AND t2.a=t1.a AND 5.1<t2.c AND t1.b='DE'
+ORDER BY t2.c LIMIT 1;
+d
+52.5
+EXPLAIN
+SELECT d FROM t3 AS t1, t2 AS t2 
+WHERE t2.b=14 AND t2.a=t1.a AND 5.1<t2.c AND t1.b='DE'
+ORDER BY t2.c LIMIT 1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	range	a,b,c	c	5	NULL	420	Using where
+1	SIMPLE	t1	ref	a	a	39	test.t2.a,const	10	Using where; Using index
+SELECT d FROM t3 AS t1, t2 AS t2 
+WHERE t2.b=14 AND t2.a=t1.a AND 5.1<t2.c AND t1.b='DE'
+ORDER BY t2.c LIMIT 1;
+d
+52.5
+DROP TABLE t1,t2,t3;

sql/sql_select.cc

@@ -13177,6 +13177,23 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
               tab->limit= select_limit;
           }
         }
+        else if (tab->type != JT_ALL)
+        {
+          /*
+            We're about to use a quick access to the table.
+            We need to change the access method so as the quick access
+            method is actually used.
+          */
+          DBUG_ASSERT(tab->select->quick);
+          tab->type=JT_ALL;
+          tab->use_quick=1;
+          tab->ref.key= -1;
+          tab->ref.key_parts=0;		// Don't use ref key.
+          tab->read_first_record= join_init_read_record;
+          /*
+            TODO: update the number of records in join->best_positions[tablenr]
+          */
+        }
       }
       used_key_parts= best_key_parts;
       order_direction= best_key_direction;