fixed problem with distinct select with grouping and subqueries (BUG#7946)

mysql-test/r/derived.result:
  DISTINCT over grouped select on subquery in the FROM clause
mysql-test/t/derived.test:
  DISTINCT over grouped select on subquery in the FROM clause
sql/sql_select.cc:
  used current join copy for test

mysql-test/r/derived.result

@@ -330,3 +330,12 @@ SELECT MIN(price) min, MAX(price) max, AVG(price) avg FROM (SELECT SUBSTRING( MA
 min	max	avg
 10.00	10.00	10
 DROP TABLE t1;
+create table t1 (a integer, b integer);
+insert into t1 values (1,4), (2,2),(2,2), (4,1),(4,1),(4,1),(4,1);
+select distinct sum(b) from t1 group by a;
+sum(b)
+4
+select distinct sum(b) from (select a,b from t1) y group by a;
+sum(b)
+4
+drop table t1;

mysql-test/t/derived.test

@@ -214,3 +214,13 @@ CREATE TABLE `t1` ( `itemid` int(11) NOT NULL default '0', `grpid` varchar(15) N
 insert into t1 values (128, 'rozn', 2, now(), 10),(128, 'rozn', 1, now(), 10);
 SELECT MIN(price) min, MAX(price) max, AVG(price) avg FROM (SELECT SUBSTRING( MAX(concat(date_,";",price)), 12) price FROM t1 WHERE itemid=128 AND  grpid='rozn' GROUP BY itemid, grpid, vendor) lastprices;
 DROP TABLE t1;
+
+#
+# DISTINCT over grouped select on subquery in the FROM clause
+#
+create table t1 (a integer, b integer);
+insert into t1 values (1,4), (2,2),(2,2), (4,1),(4,1),(4,1),(4,1);
+select distinct sum(b) from t1 group by a;
+select distinct sum(b) from (select a,b from t1) y group by a;
+drop table t1;
+

sql/sql_select.cc

@@ -1304,7 +1304,7 @@ JOIN::exec()
       curr_join->select_distinct=0;		/* Each row is unique */
     
     curr_join->join_free(0);			/* Free quick selects */
-    if (select_distinct && ! group_list)
+    if (curr_join->select_distinct && ! curr_join->group_list)
     {
       thd->proc_info="Removing duplicates";
       if (curr_join->tmp_having)