A bug fix for ORDER BY on table.column in provisional entire UNION

ORDER clause, where table is one of union'ed tables.

mysql-test/r/union.result

@@ -84,6 +84,11 @@ a	b
 3	c
 2	b
 1	a
+(select a,b from t1 limit 2)  union all (select a,b from t2 order by a limit 1) order by t1.b;
+a	b
+1	a
+2	b
+3	c
 explain (select a,b from t1 limit 2)  union all (select a,b from t2 order by a limit 1) order by b desc;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	4	

mysql-test/t/union.test

@@ -20,6 +20,7 @@ select 't1',b,count(*) from t1 group by b UNION select 't2',b,count(*) from t2 g
 (select a,b from t1 limit 2)  union all (select a,b from t2 order by a) limit 4;
 (select a,b from t1 limit 2)  union all (select a,b from t2 order by a limit 1);
 (select a,b from t1 limit 2)  union all (select a,b from t2 order by a limit 1) order by b desc;
+(select a,b from t1 limit 2)  union all (select a,b from t2 order by a limit 1) order by t1.b;
 explain (select a,b from t1 limit 2)  union all (select a,b from t2 order by a limit 1) order by b desc;
 #(select sql_calc_found_rows  a,b from t1 limit 2)  union all (select a,b from t2 order by a) limit 2;
 select found_rows();

sql/item.cc

@@ -535,9 +535,12 @@ bool Item_field::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
       SELECT_LEX *last= 0;
       
       Item **refer= (Item **)not_found_item;
+      SELECT_LEX *cursel=(SELECT_LEX *) thd->lex.current_select; 
       // Prevent using outer fields in subselects, that is not supported now
-      if (thd->lex.current_select->linkage != DERIVED_TABLE_TYPE)
-	for (SELECT_LEX *sl= thd->lex.current_select->outer_select();
+      if (cursel->linkage != DERIVED_TABLE_TYPE)
+	for (SELECT_LEX *sl= (cursel->get_master()->linkage == GLOBAL_OPTIONS_TYPE && 
+			      cursel->get_master()->order_list.elements) ?  cursel->select_lex() 
+	       : cursel->outer_select();
 	     sl;
 	     sl= sl->outer_select())
 	{