Bug#36008133 Assertion `false' failed in

 replace_embedded_rollup_references_with_tmp_fields

Regression cause by Bug#35390341 Assertion `m_count > 0 && m_count >
m_frame_null_count' failed.

That issue involved setting a user variable inside the argument of a
window function, which in turn was evaluated using the window frame
buffer (Window::m_needs_frame_buffering) row optimizable
(Window::m_row_optimizable). The first solution had an unfortunate
side-effect as seen by the present bug: here, the window function
doesn't have an argument containing the setting of a user variable, it
is the other way around: the setting of a user variable requires the
value of a window function.

Solution: refine the criterion for when we evaluate the setting of
user variable before windowing to only include the case of a wf
containing a setting (Bug#35390341).

Change-Id: Idc6824adf4bd123775a14b92bfe54824acf105c8

Author: Dag Wanvik

mysql-test/r/window_functions_bugs.result

@@ -1836,6 +1836,15 @@ SELECT @a;
 0
 DROP TABLE t1;
 #
+# Bug#36008133 Assertion `false' failed in replace_embedded_rollup_references_with_tmp_fields
+#
+CREATE TABLE t1(f1 INTEGER);
+SELECT @A := (CUME_DIST() OVER () + f1 + RANK() OVER ()) FROM t1 GROUP BY f1 WITH ROLLUP;
+@A := (CUME_DIST() OVER () + f1 + RANK() OVER ())
+Warnings:
+Warning	1287	Setting user variables within expressions is deprecated and will be removed in a future release. Consider alternatives: 'SET variable=expression, ...', or 'SELECT expression(s) INTO variables(s)'.
+DROP TABLE t1;
+#
 # Bug#35537311 nth_value window function assertion error
 #
 CREATE TABLE t0(c1 TINYINT UNSIGNED, c5 BIT);

mysql-test/t/window_functions_bugs.test

@@ -1270,6 +1270,13 @@ SELECT @a;
 
 DROP TABLE t1;
 
+--echo #
+--echo # Bug#36008133 Assertion `false' failed in replace_embedded_rollup_references_with_tmp_fields
+--echo #
+CREATE TABLE t1(f1 INTEGER);
+SELECT @A := (CUME_DIST() OVER () + f1 + RANK() OVER ()) FROM t1 GROUP BY f1 WITH ROLLUP;
+DROP TABLE t1;
+
 --echo #
 --echo # Bug#35537311 nth_value window function assertion error
 --echo #

sql/sql_executor.cc

@@ -4309,7 +4309,7 @@ bool change_to_use_tmp_fields(mem_root_deque<Item *> *fields, THD *thd,
       new_item = item->get_tmp_table_item(thd);
     else if (item->type() == Item::FUNC_ITEM &&
              ((Item_func *)item)->functype() == Item_func::SUSERVAR_FUNC &&
-             !windowing) {
+             (!windowing || item->has_wf())) {
       field = item->get_tmp_table_field();
       if (field != nullptr) {
         /*