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.


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/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.
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, 24 insertions, 0 deletions

diff --git a/mysql-test/r/cast.result b/mysql-test/r/cast.result
index 524ff48d69e..88601eceb0a 100644
--- a/mysql-test/r/cast.result
+++ b/mysql-test/r/cast.result
@@ -414,4 +414,28 @@ NULL
 NULL
 20070719
 drop table t1;
+CREATE TABLE t1 (f1 DATE);
+INSERT INTO t1 VALUES ('2007-07-19'), (NULL);
+SELECT HOUR(f1),
+MINUTE(f1),
+SECOND(f1) FROM t1;
+HOUR(f1)	MINUTE(f1)	SECOND(f1)
+0	0	0
+NULL	NULL	NULL
+SELECT HOUR(CAST('2007-07-19' AS DATE)),
+MINUTE(CAST('2007-07-19' AS DATE)),
+SECOND(CAST('2007-07-19' AS DATE));
+HOUR(CAST('2007-07-19' AS DATE))	MINUTE(CAST('2007-07-19' AS DATE))	SECOND(CAST('2007-07-19' AS DATE))
+0	0	0
+SELECT HOUR(CAST(NULL AS DATE)),
+MINUTE(CAST(NULL AS DATE)),
+SECOND(CAST(NULL AS DATE));
+HOUR(CAST(NULL AS DATE))	MINUTE(CAST(NULL AS DATE))	SECOND(CAST(NULL AS DATE))
+NULL	NULL	NULL
+SELECT HOUR(NULL),
+MINUTE(NULL),
+SECOND(NULL);
+HOUR(NULL)	MINUTE(NULL)	SECOND(NULL)
+NULL	NULL	NULL
+DROP TABLE t1;
 End of 5.0 tests