Fixed bug mdev-5382

When marking used columns the function find_field_in_table_ref() erroneously
called the walk method for the real item behind a view/derived table field
with the second parameter set to TRUE.
This erroneous code was introduced in 2006. 

mysql-test/r/union.result

@@ -1738,4 +1738,19 @@ i
 6
 DROP VIEW v1;
 DROP TABLE t1;
+#
+# mdev-5382:  UNION with ORDER BY in subselect
+#
+CREATE TABLE t1 (a int DEFAULT NULL);
+INSERT INTO t1 VALUES (2), (4);
+CREATE TABLE t2 (b int DEFAULT NULL);
+INSERT INTO t2 VALUES (1), (3);
+SELECT c1 FROM (SELECT (SELECT a FROM t1 WHERE t1.a <= t2.b
+UNION ALL
+SELECT a FROM t1 WHERE t1.a+3<= t2.b
+ORDER BY a DESC) AS c1 FROM t2) t3;
+c1
+NULL
+2
+DROP TABLE t1,t2;
 End of 5.3 tests

mysql-test/t/union.test

@@ -1227,5 +1227,21 @@ deallocate prepare stmt1;
  DROP VIEW v1;
  DROP TABLE t1;
 
+--echo #
+--echo # mdev-5382:  UNION with ORDER BY in subselect
+--echo #
+ 
+ CREATE TABLE t1 (a int DEFAULT NULL);
+ INSERT INTO t1 VALUES (2), (4);
+ CREATE TABLE t2 (b int DEFAULT NULL);
+ INSERT INTO t2 VALUES (1), (3);
+ 
+ SELECT c1 FROM (SELECT (SELECT a FROM t1 WHERE t1.a <= t2.b
+                         UNION ALL
+                         SELECT a FROM t1 WHERE t1.a+3<= t2.b
+                         ORDER BY a DESC) AS c1 FROM t2) t3;
+
+ DROP TABLE t1,t2;
+ 
  --echo End of 5.3 tests
 

sql/sql_base.cc

@@ -6429,9 +6429,9 @@ find_field_in_table_ref(THD *thd, TABLE_LIST *table_list,
           else
           {
             if (thd->mark_used_columns == MARK_COLUMNS_READ)
-              it->walk(&Item::register_field_in_read_map, 1, (uchar *) 0);
+              it->walk(&Item::register_field_in_read_map, 0, (uchar *) 0);
             else
-              it->walk(&Item::register_field_in_write_map, 1, (uchar *) 0);
+              it->walk(&Item::register_field_in_write_map, 0, (uchar *) 0);
           }
         }
         else