Bug#31990: MINUTE() and SECOND() return bogus results when used on a DATE

HOUR(), MINUTE(), ... returned spurious results when used on a DATE-cast.
This happened because DATE-cast object did not overload get_time() method
in superclass Item. The default method was inappropriate here and
misinterpreted the data.

Patch adds missing method; get_time() on DATE-casts now returns SQL-NULL
on NULL input, 0 otherwise. This coincides with the way DATE-columns
behave.

Also fixes similar bug in Date-Field now.


mysql-test/r/cast.result:
  Show that HOUR(), MINUTE(), ... return sensible values when used
  on DATE-cast objects, namely NULL for NULL-dates and 0 otherwise.
  Show that this coincides with how DATE-columns behave.
mysql-test/r/type_date.result:
  Show that HOUR(), MINUTE(), ... return sensible values when used
  on DATE-fields.
mysql-test/t/cast.test:
  Show that HOUR(), MINUTE(), ... return sensible values when used
  on DATE-cast objects, namely NULL for NULL-dates and 0 otherwise.
  Show that this coincides with how DATE-columns behave.
mysql-test/t/type_date.test:
  Show that HOUR(), MINUTE(), ... return sensible values when used
  on DATE-fields.
sql/field.cc:
  Add get_time() method to DATE-field object to overload
  the method in Field superclass that would return spurious
  results. Return zero-result.
sql/field.h:
  Add get_time() declaration to date-field class
sql/item_timefunc.cc:
  Add get_time() method to DATE-cast object to overload
  the method in Item superclass that would return spurious
  results. Return zero-result; flag NULL if input was NULL.
sql/item_timefunc.h:
  Add get_time() declaration to DATE-cast object.

1 files changed, 7 insertions, 0 deletions

diff --git a/sql/field.cc b/sql/field.cc
index 86853389c64..db438c7c4d0 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -5194,6 +5194,13 @@ String *Field_date::val_str(String *val_buffer,
 }
 
 
+bool Field_date::get_time(MYSQL_TIME *ltime)
+{
+  bzero((char *)ltime, sizeof(MYSQL_TIME));
+  return 0;
+}
+
+
 int Field_date::cmp(const char *a_ptr, const char *b_ptr)
 {
   int32 a,b;