MDEV-9780: Window functions: interplay between window function and other constructs

Implement the "DISTINCT must not be converted into GROUP BY when window
functions are present" part.

Author: spetrunia

mysql-test/r/win.result

@@ -1902,3 +1902,61 @@ part_id	pk	a	sum(a) over (partition by part_id order by pk rows between 1 preced
 200	3	4	6
 200	4	8	12
 drop table t1;
+#
+# MDEV-9780, The "DISTINCT must not bet converted into GROUP BY when
+#                 window functions are present" part 
+#
+create table t1 (part_id int, a int);
+insert into t1 values
+(100, 1),
+(100, 2),
+(100, 2),
+(100, 3),
+(2000, 1),
+(2000, 2),
+(2000, 3),
+(2000, 3),
+(2000, 3);
+select          rank() over (partition by part_id order by a) from t1;
+rank() over (partition by part_id order by a)
+1
+2
+2
+4
+1
+2
+3
+3
+3
+select distinct rank() over (partition by part_id order by a) from t1;
+rank() over (partition by part_id order by a)
+1
+2
+4
+3
+explain format=json
+select distinct rank() over (partition by part_id order by a) from t1;
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "duplicate_removal": {
+      "window_functions_computation": {
+        "sorts": {
+          "filesort": {
+            "sort_key": "t1.part_id, t1.a"
+          }
+        },
+        "temporary_table": {
+          "table": {
+            "table_name": "t1",
+            "access_type": "ALL",
+            "rows": 9,
+            "filtered": 100
+          }
+        }
+      }
+    }
+  }
+}
+drop table t1;

mysql-test/t/win.test

@@ -1164,4 +1164,27 @@ select
 from t1;
 
 drop table t1;
+--echo #
+--echo # MDEV-9780, The "DISTINCT must not bet converted into GROUP BY when
+--echo #                 window functions are present" part 
+--echo #
+
+create table t1 (part_id int, a int);
+insert into t1 values
+(100, 1),
+(100, 2),
+(100, 2),
+(100, 3),
+(2000, 1),
+(2000, 2),
+(2000, 3),
+(2000, 3),
+(2000, 3);
+
+select          rank() over (partition by part_id order by a) from t1;
+select distinct rank() over (partition by part_id order by a) from t1;
+explain format=json
+select distinct rank() over (partition by part_id order by a) from t1;
+
+drop table t1;
 

sql/sql_lex.h

@@ -1113,6 +1113,8 @@ class st_select_lex: public st_select_lex_node
     return window_funcs.push_back(win_func);
   }
 
+  bool have_window_funcs() const { return (window_funcs.elements !=0); }
+
 private:
   bool m_non_agg_field_used;
   bool m_agg_func_used;

sql/sql_select.cc

@@ -1659,7 +1659,8 @@ JOIN::optimize_inner()
       (!join_tab[const_tables].select ||
        !join_tab[const_tables].select->quick ||
        join_tab[const_tables].select->quick->get_type() != 
-       QUICK_SELECT_I::QS_TYPE_GROUP_MIN_MAX))
+       QUICK_SELECT_I::QS_TYPE_GROUP_MIN_MAX) &&
+      !select_lex->have_window_funcs())
   {
     if (group && rollup.state == ROLLUP::STATE_NONE &&
        list_contains_unique_index(join_tab[const_tables].table,
@@ -1709,11 +1710,13 @@ JOIN::optimize_inner()
   }
   if (group || tmp_table_param.sum_func_count)
   {
-    if (! hidden_group_fields && rollup.state == ROLLUP::STATE_NONE)
+    if (! hidden_group_fields && rollup.state == ROLLUP::STATE_NONE
+        && !select_lex->have_window_funcs())
       select_distinct=0;
   }
   else if (select_distinct && table_count - const_tables == 1 &&
-           rollup.state == ROLLUP::STATE_NONE)
+           rollup.state == ROLLUP::STATE_NONE &&
+           !select_lex->have_window_funcs())
   {
     /*
       We are only using one table. In this case we change DISTINCT to a
@@ -2283,7 +2286,8 @@ bool JOIN::make_aggr_tables_info()
     tmp_table_param.hidden_field_count= 
       all_fields.elements - fields_list.elements;
 
-    distinct= select_distinct && !group_list;
+    distinct= select_distinct && !group_list && 
+              !select_lex->have_window_funcs();
     keep_row_order= false;
     if (create_postjoin_aggr_table(curr_tab,
                                    &all_fields, tmp_group,