Fix sorting of NULL values (Should always be first)

Fix problem with HAVING and MAX() IS NOT NULL


Docs/manual.texi:
  Changelog & NULL usage with ORDER BY
client/mysqldump.c:
  Cleanup disable keys
mysql-test/r/distinct.result:
  Fix results after ORDER BY with NULL fix
mysql-test/r/group_by.result:
  Fix results after ORDER BY with NULL fix
mysql-test/r/having.result:
  Testcase for bug with HAVING
mysql-test/t/distinct.test:
  Test for DISTINCT + ORDER BY DESC bug
mysql-test/t/having.test:
  Test of HAVING and MAX IS NOT NULL
sql/filesort.cc:
  Fix sorting of NULL values (Should always be first)
sql/item.h:
  Fix problem with HAVING and MAX() IS NOT NULL
sql/item_sum.h:
  Fix problem with HAVING and MAX() IS NOT NULL
sql/opt_range.cc:
  Fix problem with HAVING and MAX() IS NOT NULL
sql/opt_range.h:
  Fix sorting of NULL values
sql/sql_select.cc:
  Fix sorting of ORDER BY ... DESC on NULL values.

1 files changed, 3 insertions, 0 deletions

diff --git a/sql/item_sum.h b/sql/item_sum.h
index 4840ae8298d..a963799b6a7 100644
--- a/sql/item_sum.h
+++ b/sql/item_sum.h
@@ -64,6 +64,7 @@ public:
   { return new Item_field(field);}
   table_map used_tables() const { return ~(table_map) 0; } /* Not used */
   bool const_item() const { return 0; }
+  bool is_null() { return null_value; }
   void update_used_tables() { }
   void make_field(Send_field *field);
   void print(String *str);
@@ -202,6 +203,7 @@ public:
   enum Type type() const { return FIELD_AVG_ITEM; }
   double val();
   longlong val_int() { return (longlong) val(); }
+  bool is_null() { (void) val_int(); return null_value; }
   String *val_str(String*);
   void make_field(Send_field *field);
   void fix_length_and_dec() {}
@@ -239,6 +241,7 @@ public:
   double val();
   longlong val_int() { return (longlong) val(); }
   String *val_str(String*);
+  bool is_null() { (void) val_int(); return null_value; }
   void make_field(Send_field *field);
   void fix_length_and_dec() {}
 };