Bug#29555: Comparing time values as strings may lead to a wrong result.

Time values were compared as strings. This led to a wrong comparison
result when comparing values one of which is under 100 hours and another is
over 100 hours.

Now when the Arg_comparator::set_cmp_func function sees that both items to
compare are of the TIME type it sets the comparator to the
Arg_comparator::compare_e_int or the Arg_comparator::compare_int_unsigned
functions.


sql/item_cmpfunc.cc:
  Bug#29555: Comparing time values as strings may lead to a wrong result.
  Now when the Arg_comparator::set_cmp_func function sees that both items to
  compare are of the TIME type it sets the comparator to the
  Arg_comparator::compare_e_int or the Arg_comparator::compare_int_unsigned
  functions.
mysql-test/r/type_time.result:
  Added a test case for the bug#29555: Comparing time values as strings may
  lead to a wrong result.
mysql-test/t/type_time.test:
  Added a test case for the bug#29555: Comparing time values as strings may
  lead to a wrong result.

1 files changed, 12 insertions, 0 deletions

diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index ed0c09f0b32..70df1b4d09c 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -706,6 +706,18 @@ int Arg_comparator::set_cmp_func(Item_bool_func2 *owner_arg,
     func= &Arg_comparator::compare_datetime;
     return 0;
   }
+  else if (type == STRING_RESULT && (*a)->field_type() == MYSQL_TYPE_TIME &&
+           (*b)->field_type() == MYSQL_TYPE_TIME)
+  {
+    /* Compare TIME values as integers. */
+    thd= current_thd;
+    owner= owner_arg;
+    func= ((test(owner && owner->functype() == Item_func::EQUAL_FUNC)) ?
+           &Arg_comparator::compare_e_int :
+           &Arg_comparator::compare_int_unsigned);
+    return 0;
+  }
+
   return set_compare_func(owner_arg, type);
 }