MDEV-8256 A part of a ROW comparison is erroneously optimized away

Item_func_eq's created during conversion of a ROW equality to a conjunction
of scalar equalities did not set cmp_context for its arguments properly,
so some of these created Item_func_eq could be later erroneously eliminated.

1 files changed, 8 insertions, 0 deletions

diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index c9b6b30f5b1..6e5385829a2 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -325,6 +325,14 @@ public:
   {
     return cmp.set_cmp_func(this, tmp_arg, tmp_arg + 1, true);
   }
+  bool set_cmp_func_and_arg_cmp_context()
+  {
+    if (set_cmp_func())
+      return true;
+    tmp_arg[0]->cmp_context= tmp_arg[1]->cmp_context=
+      item_cmp_type(tmp_arg[0]->result_type(), tmp_arg[1]->result_type());
+    return false;
+  }
   CHARSET_INFO *compare_collation() const
   { return cmp.cmp_collation.collation; }
   Arg_comparator *get_comparator() { return &cmp; }