MDEV-25565 Crash on 2-nd execution of SP/PS for query calculating window functions

           from view

A crash of the server happened when executing a stored procedure whose the
only query calculated window functions over a mergeable view specified
as a select from non-mergeable view. The crash could be reproduced if
the window specifications of the window functions were identical and both
contained PARTITION lists and ORDER BY lists. A crash also happened on
the second execution of the prepared statement created for such query.
If to use derived tables or CTE instead of views the problem still
manifests itself crashing the server.

When optimizing the window specifications of a window function the
server can substitute the partition lists and the order lists for
the corresponding lists from another window specification in the case
when the lists are identical. This substitution is not permanent and should
be rolled back before the second execution. It was not done and this
ultimately led to a crash when resolving the column names at the second
execution of SP/PS.

1 files changed, 12 insertions, 0 deletions

diff --git a/sql/sql_window.cc b/sql/sql_window.cc
index 612c6e692fe..3ef751bc5b9 100644
--- a/sql/sql_window.cc
+++ b/sql/sql_window.cc
@@ -479,9 +479,15 @@ int compare_window_funcs_by_window_specs(Item_window_func *win_func1,
       Let's use only one of the lists.
     */
     if (!win_spec1->name() && win_spec2->name())
+    {
+      win_spec1->save_partition_list= win_spec1->partition_list;
       win_spec1->partition_list= win_spec2->partition_list;
+    }
     else
+    {
+      win_spec2->save_partition_list= win_spec2->partition_list;
       win_spec2->partition_list= win_spec1->partition_list;
+    }
 
     cmp= compare_order_lists(win_spec1->order_list,
                              win_spec2->order_list);
@@ -494,9 +500,15 @@ int compare_window_funcs_by_window_specs(Item_window_func *win_func1,
        Let's use only one of the lists.
     */
     if (!win_spec1->name() && win_spec2->name())
+    {
+      win_spec1->save_order_list= win_spec2->order_list;
       win_spec1->order_list= win_spec2->order_list;
+    }
     else
+    {
+      win_spec1->save_order_list= win_spec2->order_list;
       win_spec2->order_list= win_spec1->order_list;
+    }
 
     cmp= compare_window_frames(win_spec1->window_frame,
                                win_spec2->window_frame);