Fix bug #24035.

This performance degradation for UPDATEs could be observed in the update
statements for which the search key cannot be converted to any valid
value of the type of the search column, like for a  the condition
int_fld=99999999999999999999999999, though it can be guaranteed here
that there is no row with such a key value. 


mysql-test/r/update.result:
  Added a test case for bug #24035.
mysql-test/t/update.test:
  Added a test case for bug #24035.
sql/opt_range.cc:
  Fix bug #24035.
  This performance degradation for could be observed in the update
  statements for which the search key cannot be converted to any valid
  value of the type of the search column, like for a  the condition
  int_fld=99999999999999999999999999, though it can be guaranteed here
  that there is no row with such a key value. 
  Now the function get_mm_leaf creates trees of the type SEL_ARG::IMPOSSIBLE 
  for such conditions that tells the range scan not to perform any search
  at all.

1 files changed, 16 insertions, 1 deletions

diff --git a/sql/opt_range.cc b/sql/opt_range.cc
index f0af4b7db2a..744d222b833 100644
--- a/sql/opt_range.cc
+++ b/sql/opt_range.cc
@@ -4296,7 +4296,22 @@ get_mm_leaf(PARAM *param, COND *conf_func, Field *field, KEY_PART *key_part,
   err= value->save_in_field_no_warnings(field, 1);
   if (err > 0 && field->cmp_type() != value->result_type())
   {
-    tree= 0;
+    if ((type == Item_func::EQ_FUNC || type == Item_func::EQUAL_FUNC) &&
+	value->result_type() == item_cmp_type(field->result_type(),
+                                              value->result_type()))
+
+    {
+      tree= new (alloc) SEL_ARG(field, 0, 0);
+      tree->type= SEL_ARG::IMPOSSIBLE;
+    }
+    else
+    {
+      /*
+        TODO: We should return trees of the type SEL_ARG::IMPOSSIBLE
+        for the cases like int_field > 999999999999999999999999 as well.
+      */
+      tree= 0;
+    }
     goto end;
   } 
   if (err < 0)