Fixed bug #32815.

The index (key_part_1, key_part-2) was erroneously considered as compatible
with the required ordering in the function test_test_if_order_by_key when 
a query with an ORDER BY clause contained a condition of the form
  key_part_1=const OR key_part_1 IS NULL 
and the order list contained only key_part_2. This happened because the value
of the const_key_parts field in the KEYUSE structure was not formed correctly
for the keys that could be used for ref_or_null access. 
This was fixed in the code of the update_ref_and_keys function.
The problem could not manifest itself for MyISAM databases because the
implementation of the keys_to_use_for_scanning() handler function always
returns an empty bitmap for the MyISAM engine.

mysql-test/r/innodb_mysql.result

@@ -1213,4 +1213,16 @@ a	b
 3	2
 1	1
 DROP TABLE t1;
+CREATE TABLE t1 (id int, type char(6), d int, INDEX idx(id,d)) ENGINE=InnoDB;
+INSERT INTO t1 VALUES 
+(191, 'member', 1), (NULL, 'member', 3), (NULL, 'member', 4), (201, 'member', 2);
+EXPLAIN SELECT * FROM t1 WHERE id=191 OR id IS NULL ORDER BY d;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	idx	NULL	NULL	NULL	3	Using where; Using filesort
+SELECT * FROM t1 WHERE id=191 OR id IS NULL ORDER BY d;
+id	type	d
+191	member	1
+NULL	member	3
+NULL	member	4
+DROP TABLE t1;
 End of 5.0 tests

mysql-test/t/innodb_mysql.test

@@ -960,4 +960,19 @@ SELECT * FROM t1 ORDER BY b DESC, a ASC;
 
 DROP TABLE t1;
 
+#
+# Bug #32815: query with ORDER BY and a possible ref_or_null access
+#
+
+CREATE TABLE t1 (id int, type char(6), d int, INDEX idx(id,d)) ENGINE=InnoDB;
+INSERT INTO t1 VALUES 
+  (191, 'member', 1), (NULL, 'member', 3), (NULL, 'member', 4), (201, 'member', 2); 
+
+EXPLAIN SELECT * FROM t1 WHERE id=191 OR id IS NULL ORDER BY d;
+SELECT * FROM t1 WHERE id=191 OR id IS NULL ORDER BY d;
+
+DROP TABLE t1;
+
+
+
 --echo End of 5.0 tests

sql/sql_select.cc

@@ -3691,7 +3691,7 @@ update_ref_and_keys(THD *thd, DYNAMIC_ARRAY *keyuse,JOIN_TAB *join_tab,
     found_eq_constant=0;
     for (i=0 ; i < keyuse->elements-1 ; i++,use++)
     {
-      if (!use->used_tables)
+      if (!use->used_tables && use->optimize != KEY_OPTIMIZE_REF_OR_NULL)
 	use->table->const_key_parts[use->key]|= use->keypart_map;
       if (use->keypart != FT_KEYPART)
       {