Fix for wrongly calculated Examined_rows in 4.0 UNION's.

sql/sql_union.cc:
  Fixing a non-critical bug in 4.0 UNION's which results in erronously 
  calculated number o fexamined rows. This value is displayed in the 
  slow query log.
  
  This is a bug number #5879.

sql/sql_union.cc

@@ -39,6 +39,7 @@ int mysql_union(THD *thd, LEX *lex,select_result *result)
   TABLE_LIST *first_table=(TABLE_LIST *)lex->select_lex.table_list.first;
   TMP_TABLE_PARAM tmp_table_param;
   select_union *union_result;
+  ha_rows examined_rows= 0;
   DBUG_ENTER("mysql_union");
 
   /* Fix tables 'to-be-unioned-from' list to point at opened tables */
@@ -202,6 +203,7 @@ int mysql_union(THD *thd, LEX *lex,select_result *result)
 		     union_result);
     if (res)
       goto exit;
+    examined_rows+= thd->examined_row_count;
     /* Needed for the following test and for records_at_start in next loop */
     table->file->info(HA_STATUS_VARIABLE);
     if (found_rows_for_union & sl->options)
@@ -258,12 +260,15 @@ int mysql_union(THD *thd, LEX *lex,select_result *result)
       if (describe)
 	thd->select_limit= HA_POS_ERROR;		// no limit
       
-      res=mysql_select(thd,&result_table_list,
+      res= mysql_select(thd,&result_table_list,
 		       item_list, NULL, (describe) ? 0 : order,
 		       (ORDER*) NULL, NULL, (ORDER*) NULL,
 		       thd->options, result);
       if (!res)
-	thd->limit_found_rows = (ulonglong)table->file->records + add_rows;
+      {
+	thd->limit_found_rows= (ulonglong)table->file->records + add_rows;
+	thd->examined_row_count+= examined_rows;
+      }
     }
   }