Fixed bug mdev-9924.

Supported queries with window functions when GROUP BY could be
optimized away.

mysql-test/r/win.result

@@ -3075,3 +3075,24 @@ select count(distinct s) from (select sum(d) as s from t group by a) Z where s >
 count(distinct s)
 1
 drop table t;
+#
+# MDEV-9924: window function in query with group by optimized away 
+#
+create table t1 (i int);
+insert into t1 values (2),(3),(1);
+select row_number() over () from t1 group by 1+2;
+row_number() over ()
+1
+select max(i), row_number() over () from t1 group by 1+2;
+max(i)	row_number() over ()
+3	1
+select rank() over (order by max(i)) from t1 group by 1+2;
+rank() over (order by max(i))
+1
+select i, row_number() over () from t1 group by 1+2;
+i	row_number() over ()
+2	1
+select i, rank() over (order by i) rnk from t1 group by 1+2;
+i	rnk
+2	1
+drop table t1;

mysql-test/t/win.test

@@ -1793,3 +1793,19 @@ select count(distinct s) from (select sum(d) over(partition by a) as s from t) Z
 select count(distinct s) from (select sum(d) as s from t group by a) Z where s > 0;
 
 drop table t;
+
+--echo #
+--echo # MDEV-9924: window function in query with group by optimized away 
+--echo #
+
+create table t1 (i int);
+insert into t1 values (2),(3),(1);
+
+select row_number() over () from t1 group by 1+2;
+select max(i), row_number() over () from t1 group by 1+2;
+select rank() over (order by max(i)) from t1 group by 1+2;
+
+select i, row_number() over () from t1 group by 1+2;
+select i, rank() over (order by i) rnk from t1 group by 1+2;
+
+drop table t1;

sql/sql_select.cc

@@ -2226,6 +2226,9 @@ bool JOIN::make_aggr_tables_info()
   
   sort_and_group_aggr_tab= NULL;
 
+  if (group_optimized_away)
+    implicit_grouping= true;
+
   bool implicit_grouping_with_window_funcs= implicit_grouping &&
                                             select_lex->have_window_funcs();
   
@@ -2574,7 +2577,7 @@ bool JOIN::make_aggr_tables_info()
     tmp_table_param.copy_field= tmp_table_param.copy_field_end=0;
     first_record= sort_and_group=0;
 
-    if (!group_optimized_away)
+    if (!group_optimized_away || implicit_grouping_with_window_funcs)
     {
       group= false;
     }