MDEV-23438: Assertion `!field->is_null()' failed in my_decimal::my_decimal fails in ONLY_FULL_GROUP_BY mode10.2-varun

The issue here is query with aggregate function and non-aggregate field
in the SELECT LIST with ONLY_FULL_GROUP_BY was not disallowed.
In ONLY_FULL_GROUP_BY mode non-aggregate fields are only allowed inside an
aggregate functions or the non-aggregate fields are part of the GROUP BY clause.

In the query for the failing assert the non-aggregate field was inside
a WINDOW function and the window function was treated as an aggregate function
and so no error was thrown.

The fix would be to make sure to mark that a non-aggregate field is used inside a
window function and not an aggregate function and throw an error then.

1 files changed, 6 insertions, 0 deletions

diff --git a/sql/item_windowfunc.cc b/sql/item_windowfunc.cc
index bb4a8a9f3af..1c97c4cb6d8 100644
--- a/sql/item_windowfunc.cc
+++ b/sql/item_windowfunc.cc
@@ -93,6 +93,12 @@ Item_window_func::fix_fields(THD *thd, Item **ref)
     my_error(ER_NO_ORDER_LIST_IN_WINDOW_SPEC, MYF(0), window_func()->func_name());
     return true;
   }
+
+  /*
+    Mark that Item_sum is used as a window function
+  */
+  window_func()->mark_as_window_func_sum_expr();
+
   /*
     TODO: why the last parameter is 'ref' in this call? What if window_func
     decides to substitute itself for something else and does *ref=.... ?