MDEV-14791: Crash with order by expression containing window functions

The issue here is that for a window function in the ORDER BY clause, we were not
creating an extra field in the temporary table for the window function
(which is contained in an expression).
So a call to split_sum_func is added to handle this case

Also we need to update all items that contain a window function
in the temp table during window function computation as filesort would need
these values to be updated to calculate the ORDER BY clause of the select.

mysql-test/r/win.result

@@ -3536,5 +3536,50 @@ AVG(0) OVER ()	MAX('2')
 0.0000	NULL
 drop table t1;
 #
+# MDEV-14791: Crash with order by expression containing window functions
+#
+CREATE TABLE t1 (b1 int, b2 int);
+INSERT INTO t1 VALUES (1,1),(0,0);
+explain
+SELECT b1 from t1 order by row_number() over (ORDER BY b2) + 1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	Using temporary; Using filesort
+SELECT b1 from t1 order by row_number() over (ORDER BY b2) + 1;
+b1
+0
+1
+explain
+SELECT b1 from t1 order by row_number() over (ORDER BY b2);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	Using temporary; Using filesort
+SELECT b1 from t1 order by row_number() over (ORDER BY b2);
+b1
+0
+1
+DROP TABLE t1;
+CREATE TABLE t1 (a int, b int, c int);
+INSERT INTO t1 VALUES (2,3,207), (1,21,909), (7,13,312), (8,64,248);
+explain
+SELECT * FROM t1 ORDER BY max(t1.a) over (partition by c);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	4	Using temporary; Using filesort
+SELECT * FROM t1 ORDER BY max(t1.a) over (partition by c);
+a	b	c
+1	21	909
+2	3	207
+7	13	312
+8	64	248
+explain
+SELECT max(t1.a) over (partition by c) as x, b, c from t1 order by max(t1.a) over (partition by c);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	4	Using temporary; Using filesort
+SELECT max(t1.a) over (partition by c) as x, b, c from t1 order by max(t1.a) over (partition by c);
+x	b	c
+1	21	909
+2	3	207
+7	13	312
+8	64	248
+drop table t1;
+#
 # End of 10.2 tests
 #

mysql-test/t/win.test

@@ -2279,6 +2279,37 @@ UNION ALL
 (SELECT AVG(0) OVER (), MAX('2') FROM t1);
 drop table t1;
 
+--echo #
+--echo # MDEV-14791: Crash with order by expression containing window functions
+--echo #
+
+CREATE TABLE t1 (b1 int, b2 int);
+INSERT INTO t1 VALUES (1,1),(0,0);
+
+explain
+SELECT b1 from t1 order by row_number() over (ORDER BY b2) + 1;
+
+SELECT b1 from t1 order by row_number() over (ORDER BY b2) + 1;
+
+explain
+SELECT b1 from t1 order by row_number() over (ORDER BY b2);
+
+SELECT b1 from t1 order by row_number() over (ORDER BY b2);
+DROP TABLE t1;
+
+CREATE TABLE t1 (a int, b int, c int);
+INSERT INTO t1 VALUES (2,3,207), (1,21,909), (7,13,312), (8,64,248);
+
+explain
+SELECT * FROM t1 ORDER BY max(t1.a) over (partition by c);
+SELECT * FROM t1 ORDER BY max(t1.a) over (partition by c);
+
+explain
+SELECT max(t1.a) over (partition by c) as x, b, c from t1 order by max(t1.a) over (partition by c);
+SELECT max(t1.a) over (partition by c) as x, b, c from t1 order by max(t1.a) over (partition by c);
+
+drop table t1;
+
 --echo #
 --echo # End of 10.2 tests
 --echo #

sql/sql_select.cc

@@ -933,8 +933,9 @@ JOIN::prepare(TABLE_LIST *tables_init,
             item->max_length)))
         real_order= TRUE;
 
-      if (item->with_sum_func && item->type() != Item::SUM_FUNC_ITEM)
-        item->split_sum_func(thd, ref_ptrs, all_fields, 0);
+      if ((item->with_sum_func && item->type() != Item::SUM_FUNC_ITEM) ||
+          item->with_window_func)
+        item->split_sum_func(thd, ref_ptrs, all_fields, SPLIT_SUM_SELECT);
     }
     if (!real_order)
       order= NULL;
@@ -26714,27 +26715,6 @@ AGGR_OP::end_send()
     }
     else
     {
-      /*
-         In case we have window functions present, an extra step is required
-         to compute all the fields from the temporary table.
-         In case we have a compound expression such as: expr + expr,
-         where one of the terms has a window function inside it, only
-         after computing window function values we actually know the true
-         final result of the compounded expression.
-
-         Go through all the func items and save their values once again in the
-         corresponding temp table fields. Do this for each row in the table.
-      */
-      if (join_tab->window_funcs_step)
-      {
-        Item **func_ptr= join_tab->tmp_table_param->items_to_copy;
-        Item *func;
-        for (; (func = *func_ptr) ; func_ptr++)
-        {
-          if (func->with_window_func)
-            func->save_in_result_field(true);
-        }
-      }
       rc= evaluate_join_record(join, join_tab, 0);
     }
   }

sql/sql_window.cc

@@ -2527,11 +2527,38 @@ bool save_window_function_values(List<Item_window_func>& window_functions,
                                  TABLE *tbl, uchar *rowid_buf)
 {
   List_iterator_fast<Item_window_func> iter(window_functions);
+  JOIN_TAB *join_tab= tbl->reginfo.join_tab;
   tbl->file->ha_rnd_pos(tbl->record[0], rowid_buf);
   store_record(tbl, record[1]);
   while (Item_window_func *item_win= iter++)
     item_win->save_in_field(item_win->result_field, true);
 
+  /*
+    In case we have window functions present, an extra step is required
+    to compute all the fields from the temporary table.
+    In case we have a compound expression such as: expr + expr,
+    where one of the terms has a window function inside it, only
+    after computing window function values we actually know the true
+    final result of the compounded expression.
+
+    Go through all the func items and save their values once again in the
+    corresponding temp table fields. Do this for each row in the table.
+
+    This needs to be done earlier because ORDER BY clause can also have
+    a window function, so we need to make sure all the fields of the temp.table
+    are updated before we do the filesort. So is best to update the other fields
+    that contain the window functions along with the computation of window
+    functions.
+  */
+
+  Item **func_ptr= join_tab->tmp_table_param->items_to_copy;
+  Item *func;
+  for (; (func = *func_ptr) ; func_ptr++)
+  {
+    if (func->with_window_func && func->type() != Item::WINDOW_FUNC_ITEM)
+      func->save_in_result_field(true);
+  }
+
   int err= tbl->file->ha_update_row(tbl->record[1], tbl->record[0]);
   if (err && err != HA_ERR_RECORD_IS_THE_SAME)
     return true;