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.

mysql-test/r/type_time.result

@@ -85,3 +85,21 @@ sec_to_time(time_to_sec(t))
 13:00:00
 09:00:00
 drop table t1;
+select cast('100:55:50' as time) < cast('24:00:00' as time);
+cast('100:55:50' as time) < cast('24:00:00' as time)
+0
+select cast('100:55:50' as time) < cast('024:00:00' as time);
+cast('100:55:50' as time) < cast('024:00:00' as time)
+0
+select cast('300:55:50' as time) < cast('240:00:00' as time);
+cast('300:55:50' as time) < cast('240:00:00' as time)
+0
+select cast('100:55:50' as time) > cast('24:00:00' as time);
+cast('100:55:50' as time) > cast('24:00:00' as time)
+1
+select cast('100:55:50' as time) > cast('024:00:00' as time);
+cast('100:55:50' as time) > cast('024:00:00' as time)
+1
+select cast('300:55:50' as time) > cast('240:00:00' as time);
+cast('300:55:50' as time) > cast('240:00:00' as time)
+1

mysql-test/t/type_time.test

@@ -40,3 +40,13 @@ drop table t1;
 # ##########################################################
 
 # End of 4.1 tests
+
+#
+# Bug#29555: Comparing time values as strings may lead to a wrong result.
+#
+select cast('100:55:50' as time) < cast('24:00:00' as time);
+select cast('100:55:50' as time) < cast('024:00:00' as time);
+select cast('300:55:50' as time) < cast('240:00:00' as time);
+select cast('100:55:50' as time) > cast('24:00:00' as time);
+select cast('100:55:50' as time) > cast('024:00:00' as time);
+select cast('300:55:50' as time) > cast('240:00:00' as time);

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);
 }