Fixed bug #18767.

The bug caused wrong result sets for union constructs of the form
(SELECT ... ORDER BY order_list1 [LIMIT n]) ORDER BY order_list2.
For such queries order lists were concatenated and limit clause was
completely neglected. 

mysql-test/r/order_by.result

@@ -788,3 +788,35 @@ a
 2
 2
 DROP TABLE t1;
+CREATE TABLE t1 (a int, b int);
+INSERT INTO t1 VALUES (1,30), (2,20), (1,10), (2,30), (1,20), (2,10);
+(SELECT b,a FROM t1 ORDER BY a,b) ORDER BY b,a;
+b	a
+10	1
+10	2
+20	1
+20	2
+30	1
+30	2
+(SELECT b FROM t1 ORDER BY b DESC) ORDER BY b ASC;
+b
+10
+10
+20
+20
+30
+30
+(SELECT b,a FROM t1 ORDER BY b,a) ORDER BY a,b;
+b	a
+10	1
+20	1
+30	1
+10	2
+20	2
+30	2
+(SELECT b,a FROM t1 ORDER by b,a LIMIT 3) ORDER by a,b;
+b	a
+10	1
+20	1
+10	2
+DROP TABLE t1;

mysql-test/t/order_by.test

@@ -545,4 +545,18 @@ SELECT a FROM t1 ORDER BY a;
 (SELECT a FROM t1) ORDER BY a;
 DROP TABLE t1;
 
+#
+# Bug #18767: global ORDER BY applied to a SELECT with ORDER BY either was
+#             ignored or 'concatened' to the latter. 
+
+CREATE TABLE t1 (a int, b int);
+INSERT INTO t1 VALUES (1,30), (2,20), (1,10), (2,30), (1,20), (2,10);
+
+(SELECT b,a FROM t1 ORDER BY a,b) ORDER BY b,a;
+(SELECT b FROM t1 ORDER BY b DESC) ORDER BY b ASC;
+(SELECT b,a FROM t1 ORDER BY b,a) ORDER BY a,b;
+(SELECT b,a FROM t1 ORDER by b,a LIMIT 3) ORDER by a,b;
+
+DROP TABLE t1;
+
 # End of 4.1 tests

sql/sql_lex.h

@@ -400,6 +400,7 @@ class st_select_lex_unit: public st_select_lex_node {
   bool check_updateable(char *db, char *table);
   void print(String *str);
 
+  bool add_fake_select_lex(THD *thd);
   ulong init_prepare_fake_select_lex(THD *thd);
   int change_result(select_subselect *result, select_subselect *old_result);
   inline bool is_prepared() { return prepared; }

sql/sql_parse.cc

@@ -4189,23 +4189,9 @@ mysql_new_select(LEX *lex, bool move_down)
   else
   {
     select_lex->include_neighbour(lex->current_select);
-    SELECT_LEX_UNIT *unit= select_lex->master_unit();
-    SELECT_LEX *fake= unit->fake_select_lex;
-    if (!fake)
-    {
-      /*
-	as far as we included SELECT_LEX for UNION unit should have
-	fake SELECT_LEX for UNION processing
-      */
-      if (!(fake= unit->fake_select_lex= new(lex->thd->mem_root) SELECT_LEX()))
-        return 1;
-      fake->include_standalone(unit,
-			       (SELECT_LEX_NODE**)&unit->fake_select_lex);
-      fake->select_number= INT_MAX;
-      fake->make_empty_select();
-      fake->linkage= GLOBAL_OPTIONS_TYPE;
-      fake->select_limit= HA_POS_ERROR;
-    }
+    if (!select_lex->master_unit()->fake_select_lex &&
+        select_lex->master_unit()->add_fake_select_lex(lex->thd))
+      return 1;
   }
 
   select_lex->master_unit()->global_parameters= select_lex;
@@ -4975,6 +4961,60 @@ void st_select_lex::set_lock_for_tables(thr_lock_type lock_type)
 }
 
 
+/*
+  Create a fake SELECT_LEX for a unit
+
+  SYNOPSIS:
+    add_fake_select_lex()
+    thd			   thread handle
+
+  DESCRIPTION
+    The method create a fake SELECT_LEX object for a unit.
+    This object is created for any union construct containing a union
+    operation and also for any single select union construct of the form
+    (SELECT ... ORDER BY order_list [LIMIT n]) ORDER BY ... 
+    or of the form
+    (SELECT ... ORDER BY LIMIT n) ORDER BY ...
+  
+  NOTES
+    The object is used to retrieve rows from the temporary table
+    where the result on the union is obtained.
+
+  RETURN VALUES
+    1     on failure to create the object
+    0     on success
+*/
+
+bool st_select_lex_unit::add_fake_select_lex(THD *thd)
+{
+  SELECT_LEX *first_sl= first_select();
+  DBUG_ENTER("add_fake_select_lex");
+  DBUG_ASSERT(!fake_select_lex);
+  
+  if (!(fake_select_lex= new (thd->mem_root) SELECT_LEX()))
+      DBUG_RETURN(1);
+  fake_select_lex->include_standalone(this, 
+                                      (SELECT_LEX_NODE**)&fake_select_lex);
+  fake_select_lex->select_number= INT_MAX;
+  fake_select_lex->make_empty_select();
+  fake_select_lex->linkage= GLOBAL_OPTIONS_TYPE;
+  fake_select_lex->select_limit= HA_POS_ERROR;
+
+  if (!first_sl->next_select())
+  {
+    /* 
+      This works only for 
+      (SELECT ... ORDER BY list [LIMIT n]) ORDER BY order_list [LIMIT m],
+      (SELECT ... LIMIT n) ORDER BY order_list [LIMIT m]
+      just before the parser starts processing order_list
+    */ 
+    global_parameters= fake_select_lex;
+    fake_select_lex->no_table_names_allowed= 1;
+    thd->lex->current_select= fake_select_lex;
+  }
+  DBUG_RETURN(0);
+}
+
 void add_join_on(TABLE_LIST *b,Item *expr)
 {
   if (expr)

sql/sql_select.cc

@@ -171,7 +171,7 @@ int 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())
+  if (select_lex->next_select() || select_lex->master_unit()->fake_select_lex)
     res=mysql_union(thd, lex, result, &lex->unit);
   else
     res= mysql_select(thd, &select_lex->ref_pointer_array,

sql/sql_union.cc

@@ -184,7 +184,7 @@ int st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
   
   thd_arg->lex->current_select= sl= first_select= first_select_in_union();
   found_rows_for_union= first_select->options & OPTION_FOUND_ROWS;
-  is_union= test(first_select->next_select());
+  is_union= test(first_select->next_select() || fake_select_lex);
 
   /* Global option */
 

sql/sql_yacc.yy

@@ -3790,15 +3790,33 @@ order_clause:
 	ORDER_SYM BY
         {
 	  LEX *lex=Lex;
-	  if (lex->current_select->linkage != GLOBAL_OPTIONS_TYPE &&
-	      lex->current_select->olap !=
-	      UNSPECIFIED_OLAP_TYPE)
+          SELECT_LEX *sel= lex->current_select;
+          SELECT_LEX_UNIT *unit= sel-> master_unit();
+	  if (sel->linkage != GLOBAL_OPTIONS_TYPE &&
+	      sel->olap != UNSPECIFIED_OLAP_TYPE)
 	  {
 	    net_printf(lex->thd, ER_WRONG_USAGE,
 		       "CUBE/ROLLUP",
 		       "ORDER BY");
 	    YYABORT;
 	  }
+          if (lex->sql_command != SQLCOM_ALTER_TABLE && !unit->fake_select_lex)
+          {
+            /*
+              A query of the of the form (SELECT ...) ORDER BY order_list is
+              executed in the same way as the query
+              SELECT ... ORDER BY order_list
+              unless the SELECT construct contains ORDER BY or LIMIT clauses.
+              Otherwise we create a fake SELECT_LEX if it has not been created
+              yet.
+            */
+            SELECT_LEX *first_sl= unit->first_select();
+            if (!first_sl->next_select() &&
+                (first_sl->order_list.elements || 
+                 first_sl->select_limit != HA_POS_ERROR) &&            
+                unit->add_fake_select_lex(lex->thd))
+              YYABORT;
+          }
 	} order_list;
 
 order_list: