Oler Blasco (<notifications@github.com>)'s fix for FQS.

Thanks a lot for the contribution!

	modified:   src/backend/optimizer/util/pgxcship.c
	modified:   src/test/regress/expected/xc_FQS.out

src/backend/optimizer/util/pgxcship.c

@@ -995,6 +995,12 @@ pgxc_shippability_walker(Node *node, Shippability_context *sc_context)
 				!pgxc_query_has_distcolgrouping(query, sc_context->sc_exec_nodes))
 				pgxc_set_shippability_reason(sc_context, SS_NEED_SINGLENODE);
 
+                         /* Grouping by non distribution column can not be FQS*/
+                         if (query->groupClause != NULL &&  
+                               sc_context->sc_exec_nodes &&
+                               !pgxc_query_has_distcolgrouping(query, sc_context->sc_exec_nodes))
+                               pgxc_set_shippability_reason(sc_context, SS_NEED_SINGLENODE);
+
 			/*
 			 * If distribution column of any relation is present in the distinct
 			 * clause, values for that column across nodes will differ, thus two

src/test/regress/expected/xc_FQS.out

@@ -176,12 +176,14 @@ select val, val2 from tab1_rr where val2 = 8 group by val, val2;
 (1 row)
 
 explain (costs off, verbose on, nodes off) select val, val2 from tab1_rr where val2 = 8 group by val, val2;
-                                        QUERY PLAN                                        
-------------------------------------------------------------------------------------------
- Data Node Scan on "__REMOTE_FQS_QUERY__"
+                                           QUERY PLAN                                           
+------------------------------------------------------------------------------------------------
+ HashAggregate
    Output: tab1_rr.val, tab1_rr.val2
-   Remote query: SELECT val, val2 FROM public.tab1_rr WHERE (val2 = 8) GROUP BY val, val2
-(3 rows)
+   ->  Data Node Scan on "__REMOTE_GROUP_QUERY__"
+         Output: tab1_rr.val, tab1_rr.val2
+         Remote query: SELECT val, val2 FROM ONLY public.tab1_rr WHERE (val2 = 8) GROUP BY 1, 2
+(5 rows)
 
 -- should not get FQSed because of presence of aggregates and HAVING clause,
 select sum(val) from tab1_rr where val2 = 2 group by val2 having sum(val) > 1;