Fixes for OPTION_FOUND_ROWS in UNION's

mysql-test/r/subselect.result:
  A warning added to subselect test due to the recent changes.
  
  UNION in sub-select returns the empty set, which is why this warning is
  a mistery to me.
mysql-test/r/union.result:
  two changes.
  
  First one is due to the proper handling of LIMIT offset, limit in 
  UNION without all.
  
  Second is a change in behaviour due to the fact that ORDER by in a 
  UNION without braces is not now applicable to the last SELECT node.
  
  It can not be applied until one bug is fixed (after my vacation).
  
  Should be documented.

mysql-test/r/subselect.result

@@ -1046,6 +1046,8 @@ t1	CREATE TABLE `t1` (
 ) TYPE=MyISAM CHARSET=latin1
 drop table t1;
 CREATE TABLE t1 SELECT (SELECT 1 as a UNION SELECT 1+1 limit 1,1) as a;
+Warnings:
+Warning	1262	Data truncated, NULL supplied to NOT NULL column 'a' at row 1
 SHOW CREATE TABLE t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (

mysql-test/r/union.result

@@ -409,7 +409,7 @@ found_rows()
 SELECT SQL_CALC_FOUND_ROWS * FROM t1 UNION SELECT * FROM t2 LIMIT 2,2;
 a
 3
-4
+5
 select found_rows();
 found_rows()
 6
@@ -423,7 +423,7 @@ found_rows()
 5
 SELECT * FROM t1 UNION SELECT * FROM t2 ORDER BY a desc LIMIT 1;
 a
-5
+3
 (SELECT * FROM t1 ORDER by a) UNION ALL (SELECT * FROM t2 ORDER BY a) ORDER BY A desc LIMIT 4;
 a
 5

sql/sql_parse.cc

@@ -1729,7 +1729,7 @@ mysql_execute_command(THD *thd)
     if (unit->select_limit_cnt <
 	(ha_rows) unit->global_parameters->select_limit)
       unit->select_limit_cnt= HA_POS_ERROR;		// no limit
-    if (unit->select_limit_cnt == HA_POS_ERROR)
+    if (unit->select_limit_cnt == HA_POS_ERROR && !select_lex->next_select())
       select_lex->options&= ~OPTION_FOUND_ROWS;
 
     if (!(res=open_and_lock_tables(thd,tables)))

sql/sql_union.cc

@@ -281,7 +281,7 @@ int st_select_lex_unit::exec()
 	  */
 	  sl->options|= found_rows_for_union;
 	}
-	
+	sl->join->select_options=sl->options;
 	/*
 	  As far as union share table space we should reassign table map,
 	  which can be spoiled by 'prepare' of JOIN of other UNION parts
@@ -311,6 +311,7 @@ int st_select_lex_unit::exec()
 	records_at_start= table->file->records;
 	sl->join->exec();
 	res= sl->join->error;
+	offset_limit_cnt= sl->offset_limit;
 	if (!res && union_result->flush())
 	{
 	  thd->lex.current_select= lex_select_save;
@@ -332,7 +333,7 @@ int st_select_lex_unit::exec()
 	  We get this from the difference of between total number of possible
 	  rows and actual rows added to the temporary table.
 	*/
-	add_rows+= (ha_rows) (thd->limit_found_rows - (ulonglong)
+	add_rows+= (ulonglong) (thd->limit_found_rows - (ulonglong)
 			      ((table->file->records -  records_at_start)));
       }
     }