- addendum of the fix for bug 27786:

  applied the new function is_union() to places
  in the code that check the same condition.
- 5.0->5.1 merge fixes


mysql-test/r/subselect3.result:
  merge 5.0->5.1 : updated explain.
sql/item_subselect.cc:
  addendum of the fix for bug 27786:
  applied the new function is_union() to the applicable places.
sql/sql_derived.cc:
  addendum of the fix for bug 27786:
  applied the new function is_union() to the applicable places.
sql/sql_parse.cc:
  addendum of the fix for bug 27786:
  applied the new function is_union() to the applicable places.
sql/sql_select.cc:
  addendum of the fix for bug 27786:
  applied the new function is_union() to places 
  in the code that check the same condition.
sql/sql_union.cc:
  addendum of the fix for bug 27786:
  applied the new function is_union() to the applicable places.
sql/sql_view.cc:
  addendum of the fix for bug 27786:
  applied the new function is_union() to the applicable places.
sql/sql_yacc.yy:
  addendum of the fix for bug 27786:
  applied the new function is_union() to the applicable places.

mysql-test/r/subselect3.result

@@ -698,10 +698,10 @@ INSERT INTO t1 VALUES (1), (NULL), (4);
 INSERT INTO t2 VALUES (3), (1),(2), (5), (4), (7), (6);
 EXPLAIN EXTENDED 
 SELECT a FROM t1, t2 WHERE a=b AND (b NOT IN (SELECT a FROM t1));
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
-1	PRIMARY	t2	eq_ref	PRIMARY	PRIMARY	4	test.t1.a	1	Using index
-2	DEPENDENT SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
+1	PRIMARY	t2	eq_ref	PRIMARY	PRIMARY	4	test.t1.a	1	100.00	Using index
+2	DEPENDENT SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
 Warnings:
 Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` join `test`.`t2` where ((`test`.`t2`.`b` = `test`.`t1`.`a`) and (not(<in_optimizer>(`test`.`t1`.`a`,<exists>(select 1 AS `Not_used` from `test`.`t1` where ((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`a`) or isnull(`test`.`t1`.`a`)) having <is_not_null_test>(`test`.`t1`.`a`))))))
 SELECT a FROM t1, t2 WHERE a=b AND (b NOT IN (SELECT a FROM t1));

sql/item_subselect.cc

@@ -82,7 +82,7 @@ void Item_subselect::init(st_select_lex *select_lex,
     parsing_place= (outer_select->in_sum_expr ?
                     NO_MATTER :
                     outer_select->parsing_place);
-    if (select_lex->next_select())
+    if (unit->is_union())
       engine= new subselect_union_engine(unit, result, this);
     else
       engine= new subselect_single_select_engine(select_lex, result, this);
@@ -412,7 +412,7 @@ Item_singlerow_subselect::select_transformer(JOIN *join)
   SELECT_LEX *select_lex= join->select_lex;
   Query_arena *arena= thd->stmt_arena;
  
-  if (!select_lex->master_unit()->first_select()->next_select() &&
+  if (!select_lex->master_unit()->is_union() &&
       !select_lex->table_list.elements &&
       select_lex->item_list.elements == 1 &&
       !select_lex->item_list.head()->with_sum_func &&
@@ -1147,7 +1147,7 @@ Item_in_subselect::single_value_transformer(JOIN *join,
     else
     {
       bool tmp;
-      if (select_lex->master_unit()->first_select()->next_select())
+      if (select_lex->master_unit()->is_union())
       {
 	/*
 	  comparison functions can't be changed during fix_fields()

sql/sql_derived.cc

@@ -236,9 +236,7 @@ bool mysql_derived_filling(THD *thd, LEX *lex, TABLE_LIST *orig_table_list)
     SELECT_LEX *first_select= unit->first_select();
     select_union *derived_result= orig_table_list->derived_result;
     SELECT_LEX *save_current_select= lex->current_select;
-    bool is_union= first_select->next_select() &&
-      first_select->next_select()->linkage == UNION_TYPE;
-    if (is_union)
+    if (unit->is_union())
     {
       // execute union without clean up
       res= unit->exec();

sql/sql_parse.cc

@@ -5893,7 +5893,7 @@ bool st_select_lex_unit::add_fake_select_lex(THD *thd_arg)
   fake_select_lex->context.resolve_in_select_list= TRUE;
   fake_select_lex->context.select_lex= fake_select_lex;
 
-  if (!first_sl->next_select())
+  if (!is_union())
   {
     /* 
       This works only for 

sql/sql_select.cc

@@ -231,7 +231,8 @@ bool handle_select(THD *thd, LEX *lex, select_result *result,
   register SELECT_LEX *select_lex = &lex->select_lex;
   DBUG_ENTER("handle_select");
 
-  if (select_lex->next_select() || select_lex->master_unit()->fake_select_lex)
+  if (select_lex->master_unit()->is_union() || 
+      select_lex->master_unit()->fake_select_lex)
     res= mysql_union(thd, lex, result, &lex->unit, setup_tables_done_option);
   else
   {
@@ -442,7 +443,7 @@ JOIN::prepare(Item ***rref_pointer_array,
   select_lex= select_lex_arg;
   select_lex->join= this;
   join_list= &select_lex->top_join_list;
-  union_part= (unit_arg->first_select()->next_select() != 0);
+  union_part= unit_arg->is_union();
 
   thd->lex->current_select->is_item_list_lookup= 1;
   /*
@@ -1191,7 +1192,7 @@ JOIN::optimize()
   if (!group_list && !order &&
       unit->item && unit->item->substype() == Item_subselect::IN_SUBS &&
       tables == 1 && conds &&
-      !unit->first_select()->next_select())
+      !unit->is_union())
   {
     if (!having)
     {
@@ -3165,7 +3166,7 @@ add_key_fields(JOIN *join, KEY_FIELD **key_fields, uint *and_level,
       if (!join->group_list && !join->order &&
           join->unit->item && 
           join->unit->item->substype() == Item_subselect::IN_SUBS &&
-          !join->unit->first_select()->next_select())
+          !join->unit->is_union())
       {
         KEY_FIELD *save= *key_fields;
         add_key_fields(join, key_fields, and_level, cond_arg, usable_tables,
@@ -15523,7 +15524,7 @@ bool mysql_explain_union(THD *thd, SELECT_LEX_UNIT *unit, select_result *result)
 		 "UNION")));
     sl->options|= SELECT_DESCRIBE;
   }
-  if (first->next_select())
+  if (unit->is_union())
   {
     unit->fake_select_lex->select_number= UINT_MAX; // jost for initialization
     unit->fake_select_lex->type= "UNION RESULT";

sql/sql_union.cc

@@ -165,7 +165,7 @@ bool st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
   SELECT_LEX *lex_select_save= thd_arg->lex->current_select;
   SELECT_LEX *sl, *first_sl= first_select();
   select_result *tmp_result;
-  bool is_union;
+  bool is_union_select;
   TABLE *empty_table= 0;
   DBUG_ENTER("st_select_lex_unit::prepare");
 
@@ -203,11 +203,11 @@ bool st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
   
   thd_arg->lex->current_select= sl= first_sl;
   found_rows_for_union= first_sl->options & OPTION_FOUND_ROWS;
-  is_union= first_sl->next_select() || fake_select_lex;
+  is_union_select= is_union() || fake_select_lex;
 
   /* Global option */
 
-  if (is_union)
+  if (is_union_select)
   {
     if (!(tmp_result= union_result= new select_union))
       goto err;
@@ -238,7 +238,7 @@ bool st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
 
     thd_arg->lex->current_select= sl;
 
-    can_skip_order_by= is_union && !(sl->braces && sl->explicit_limit);
+    can_skip_order_by= is_union_select && !(sl->braces && sl->explicit_limit);
 
     saved_error= join->prepare(&sl->ref_pointer_array,
                                (TABLE_LIST*) sl->table_list.first,
@@ -251,7 +251,7 @@ bool st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
                                (ORDER*) 0 : (ORDER *)sl->order_list.first,
                                (ORDER*) sl->group_list.first,
                                sl->having,
-                               (is_union ? (ORDER*) 0 :
+                               (is_union_select ? (ORDER*) 0 :
                                 (ORDER*) thd_arg->lex->proc_list.first),
                                sl, this);
     /* There are no * in the statement anymore (for PS) */
@@ -264,7 +264,7 @@ bool st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
       Use items list of underlaid select for derived tables to preserve
       information about fields lengths and exact types
     */
-    if (!is_union)
+    if (!is_union_select)
       types= first_sl->item_list;
     else if (sl == first_sl)
     {
@@ -307,7 +307,7 @@ bool st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
     }
   }
 
-  if (is_union)
+  if (is_union_select)
   {
     /*
       Check that it was possible to aggregate
@@ -639,7 +639,7 @@ void st_select_lex_unit::reinit_exec_mechanism()
 {
   prepared= optimized= executed= 0;
 #ifndef DBUG_OFF
-  if (first_select()->next_select())
+  if (is_union())
   {
     List_iterator_fast<Item> it(item_list);
     Item *field;
@@ -706,7 +706,6 @@ bool st_select_lex_unit::change_result(select_subselect *new_result,
 List<Item> *st_select_lex_unit::get_unit_column_types()
 {
   SELECT_LEX *sl= first_select();
-  bool is_union= test(sl->next_select());
   bool is_procedure= test(sl->join->procedure);
 
   if (is_procedure)
@@ -717,7 +716,7 @@ List<Item> *st_select_lex_unit::get_unit_column_types()
   }
 
 
-  if (is_union)
+  if (is_union())
   {
     DBUG_ASSERT(prepared);
     /* Types are generated during prepare */

sql/sql_view.cc

@@ -818,7 +818,7 @@ static int mysql_register_view(THD *thd, TABLE_LIST *view,
     UNION
   */
   if (view->updatable_view &&
-      !lex->select_lex.next_select() &&
+      !lex->select_lex.master_unit()->is_union() &&
       !((TABLE_LIST*)lex->select_lex.table_list.first)->next_local &&
       find_table_in_global_list(lex->query_tables->next_global,
 				lex->query_tables->db,

sql/sql_yacc.yy

@@ -7817,7 +7817,7 @@ order_clause:
               yet.
             */
             SELECT_LEX *first_sl= unit->first_select();
-            if (!first_sl->next_select() &&
+            if (!unit->is_union() &&
                 (first_sl->order_list.elements || 
                  first_sl->select_limit) &&            
                 unit->add_fake_select_lex(lex->thd))