samall optimisation (any independent query will not save data for rexecution)

saving/restoring join_tab array (to save it of chnging by create_sort_index() before reexecuting)
(BUG#1523)

mysql-test/r/subselect.result

@@ -1439,3 +1439,14 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	3	Using where
 2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	4	Using temporary; Using filesort
 drop table if exists t2, t3;
+CREATE TABLE t1 (number char(11) NOT NULL default '') TYPE=MyISAM CHARSET=latin1;
+INSERT INTO t1 VALUES ('69294728265'),('18621828126'),('89356874041'),('95895001874');
+CREATE TABLE t2 (code char(5) NOT NULL default '',UNIQUE KEY code (code)) TYPE=MyISAM CHARSET=latin1;
+INSERT INTO t2 VALUES ('1'),('1226'),('1245'),('1862'),('18623'),('1874'),('1967'),('6');
+select c.number as phone,(select p.code from t2 p where c.number like concat(p.code, '%') order by length(p.code) desc limit 1) as code from t1 c;
+phone	code
+69294728265	6
+18621828126	1862
+89356874041	NULL
+95895001874	NULL
+drop table t1, t2;

mysql-test/t/subselect.test

@@ -965,3 +965,13 @@ insert into t2 values (2,2), (2,1), (3,3), (3,1);
 select * from t3 where a > all (select max(b) from t2 group by a);
 explain select * from t3 where a > all (select max(b) from t2 group by a);
 drop table if exists t2, t3;
+
+#
+# filesort in subquery (restoring join_tab)
+#
+CREATE TABLE t1 (number char(11) NOT NULL default '') TYPE=MyISAM CHARSET=latin1;
+INSERT INTO t1 VALUES ('69294728265'),('18621828126'),('89356874041'),('95895001874');
+CREATE TABLE t2 (code char(5) NOT NULL default '',UNIQUE KEY code (code)) TYPE=MyISAM CHARSET=latin1;
+INSERT INTO t2 VALUES ('1'),('1226'),('1245'),('1862'),('18623'),('1874'),('1967'),('6');
+select c.number as phone,(select p.code from t2 p where c.number like concat(p.code, '%') order by length(p.code) desc limit 1) as code from t1 c;
+drop table t1, t2;

sql/sql_select.cc

@@ -980,8 +980,7 @@ JOIN::optimize()
       }
     }
     
-    if (select_lex != &thd->lex.select_lex &&
-	select_lex->linkage != DERIVED_TABLE_TYPE)
+    if (select_lex->master_unit()->dependent)
     {
       if (!(tmp_join= (JOIN*)thd->alloc(sizeof(JOIN))))
 	DBUG_RETURN(-1);
@@ -994,10 +993,10 @@ JOIN::optimize()
   DBUG_RETURN(0);
 }
 
+
 /*
   Restore values in temporary join
 */
-
 void JOIN::restore_tmp()
 {
   memcpy(tmp_join, this, (size_t) sizeof(JOIN));
@@ -1039,12 +1038,29 @@ JOIN::reinit()
   if (items0)
     set_items_ref_array(items0);
 
+  if (join_tab_save)
+    memcpy(join_tab, join_tab_save, sizeof(JOIN_TAB) * tables);
+
   if (tmp_join)
     restore_tmp();
 
   DBUG_RETURN(0);
 }
 
+
+bool
+JOIN::save_join_tab()
+{
+  if (!join_tab_save && select_lex->master_unit()->dependent)
+  {
+    if (!(join_tab_save= (JOIN_TAB*) thd->alloc(sizeof(JOIN_TAB) * tables)))
+      return 1;
+    memcpy(join_tab_save, join_tab, sizeof(JOIN_TAB) * tables);
+  }
+  return 0;
+}
+
+
 /*
   Exec select
 */
@@ -1246,6 +1262,10 @@ JOIN::exec()
       if (curr_join->group_list)
       {
 	thd->proc_info= "Creating sort index";
+	if (curr_join->join_tab == join_tab && save_join_tab())
+	{
+	  DBUG_VOID_RETURN;
+	}
 	if (create_sort_index(thd, curr_join, curr_join->group_list,
 			      HA_POS_ERROR, HA_POS_ERROR) ||
 	    make_group_fields(this, curr_join))
@@ -1427,6 +1447,10 @@ JOIN::exec()
 	  }
 	}
       }
+      if (curr_join->join_tab == join_tab && save_join_tab())
+      {
+	DBUG_VOID_RETURN;
+      }
       if (create_sort_index(thd, curr_join,
 			    curr_join->group_list ? 
 			    curr_join->group_list : curr_join->order,

sql/sql_select.h

@@ -131,6 +131,7 @@ class JOIN :public Sql_alloc
 {
  public:
   JOIN_TAB *join_tab,**best_ref,**map2table;
+  JOIN_TAB *join_tab_save; //saved join_tab for subquery reexecution
   TABLE    **table,**all_tables,*sort_by_table;
   uint	   tables,const_tables;
   uint	   send_group_parts;
@@ -202,7 +203,7 @@ class JOIN :public Sql_alloc
   void init(THD *thd_arg, List<Item> &fields, ulong select_options_arg,
        select_result *result_arg)
   {
-    join_tab= 0;
+    join_tab= join_tab_save= 0;
     table= 0;
     tables= 0;
     const_tables= 0;
@@ -242,7 +243,7 @@ class JOIN :public Sql_alloc
     zero_result_cause= 0;
     optimized= 0;
 
-    fields_list = fields;
+    fields_list= fields;
     bzero((char*) &keyuse,sizeof(keyuse));
     tmp_table_param.copy_field=0;
     tmp_table_param.end_write_records= HA_POS_ERROR;
@@ -280,6 +281,7 @@ class JOIN :public Sql_alloc
   int rollup_send_data(uint idx);
   bool test_in_subselect(Item **where);
   void clear();
+  bool save_join_tab();
 };