Fixed bug mdev-9028.

This patch is actually a complement for the fix of bug mdev-6892.
The procedure create_tmp_table() now must take into account
Item_direct_refs that wrap up constant fields of derived tables/views
that are used as inner tables in outer join operations.

mysql-test/r/derived.result

@@ -988,4 +988,27 @@ David	Yes	210
 Edward	Yes	150
 DROP TABLE example1463;
 set sql_mode= @save_sql_mode;
+#
+# MDEV-9028: SELECT DISTINCT constant column of  derived  table
+#            used as the second operand of LEFT JOIN
+#
+create table t1 (id int, data varchar(255));
+insert into t1 values (1,'yes'),(2,'yes');
+select distinct t1.id, tt.id, tt.data
+from t1
+left join
+(select t1.id, 'yes' as data from t1) as tt
+on t1.id = tt.id;
+id	id	data
+1	1	yes
+2	2	yes
+select distinct t1.id, tt.id, tt.data
+from t1
+left join
+(select t1.id, 'yes' as data from t1 where id > 1) as tt
+on t1.id = tt.id;
+id	id	data
+2	2	yes
+1	NULL	NULL
+drop table t1;
 # end of 5.5

mysql-test/t/derived.test

@@ -842,4 +842,27 @@ SELECT Customer, Success, SUM(OrderSize)
 DROP TABLE example1463;
 set sql_mode= @save_sql_mode;
 
+--echo #
+--echo # MDEV-9028: SELECT DISTINCT constant column of  derived  table
+--echo #            used as the second operand of LEFT JOIN
+--echo #
+
+create table t1 (id int, data varchar(255));
+insert into t1 values (1,'yes'),(2,'yes');
+
+select distinct t1.id, tt.id, tt.data
+  from t1
+       left join
+       (select t1.id, 'yes' as data from t1) as tt
+       on t1.id = tt.id;
+
+select distinct t1.id, tt.id, tt.data
+  from t1
+       left join
+       (select t1.id, 'yes' as data from t1 where id > 1) as tt
+       on t1.id = tt.id;
+
+drop table t1;
+
+
 --echo # end of 5.5

sql/sql_select.cc

@@ -14627,7 +14627,9 @@ static Field *create_tmp_field_from_item(THD *thd, Item *item, TABLE *table,
   if (new_field)
     new_field->init(table);
     
-  if (copy_func && item->real_item()->is_result_field())
+  if (copy_func &&
+      (item->is_result_field() || 
+       (item->real_item()->is_result_field())))
     *((*copy_func)++) = item;			// Save for copy_funcs
   if (modify_item)
     item->set_result_field(new_field);