MDEV-33665: MSAN failure due to uninitialized Item_func::not_null_tables_cache

eliminate_item_equal() uses quick_fix_field() for Item objects it creates. It computes some of their attributes on its own (see update_used_tables() call) but it doesn't update not_null_tables_cache. Recompute not_null_tables_cache also. Not computing it is currently harmless, except for producing MSAN error when some other code propagates the wrong value of not_null_tables_cache to other item.

Author: spetrunia

sql/sql_select.cc

@@ -16209,6 +16209,7 @@ Item *eliminate_item_equal(THD *thd, COND *cond, COND_EQUAL *upper_levels,
 
  if (!eq_item || eq_item->set_cmp_func(thd))
  return 0;
+ eq_item->eval_not_null_tables(0);
  eq_item->quick_fix_field();
  }
  current_sjm= field_sjm;
@@ -16266,6 +16267,7 @@ Item *eliminate_item_equal(THD *thd, COND *cond, COND_EQUAL *upper_levels,
  {
  res->quick_fix_field();
  res->update_used_tables();
+ res->eval_not_null_tables(0);
  }
 
  return res;