Bug#59330: Incorrect result when comparing an aggregate function with

TIMESTAMP.

Item_cache::get_cache wasn't treating TIMESTAMP as a DATETIME value thus
returning string cache for items with TIMESTAMP type. This led to incorrect
TIMESTAMP -> INT conversion and to a wrong query result.

Fixed by using Item::is_datetime function to check for DATETIME type group.

mysql-test/r/type_timestamp.result

@@ -540,3 +540,32 @@ a
 2010-03-05 11:08:02
 DROP TABLE t1;
 End of Bug#50888
+#
+# Bug59330: Incorrect result when comparing an aggregate
+#           function with TIMESTAMP
+#
+CREATE TABLE t1 (dt DATETIME, ts TIMESTAMP);
+INSERT INTO t1 VALUES('2011-01-06 12:34:30', '2011-01-06 12:34:30');
+SELECT MAX(dt), MAX(ts) FROM t1;
+MAX(dt)	MAX(ts)
+2011-01-06 12:34:30	2011-01-06 12:34:30
+SELECT MAX(ts) < '2010-01-01 00:00:00' FROM t1;
+MAX(ts) < '2010-01-01 00:00:00'
+0
+SELECT MAX(dt) < '2010-01-01 00:00:00' FROM t1;
+MAX(dt) < '2010-01-01 00:00:00'
+0
+SELECT MAX(ts) > '2010-01-01 00:00:00' FROM t1;
+MAX(ts) > '2010-01-01 00:00:00'
+1
+SELECT MAX(dt) > '2010-01-01 00:00:00' FROM t1;
+MAX(dt) > '2010-01-01 00:00:00'
+1
+SELECT MAX(ts) = '2011-01-06 12:34:30' FROM t1;
+MAX(ts) = '2011-01-06 12:34:30'
+1
+SELECT MAX(dt) = '2011-01-06 12:34:30' FROM t1;
+MAX(dt) = '2011-01-06 12:34:30'
+1
+DROP TABLE t1;
+End of 5.5 tests

mysql-test/t/type_timestamp.test

@@ -377,3 +377,21 @@ SELECT a FROM t1;
 DROP TABLE t1;
 
 --echo End of Bug#50888
+
+--echo #
+--echo # Bug59330: Incorrect result when comparing an aggregate
+--echo #           function with TIMESTAMP
+--echo #
+CREATE TABLE t1 (dt DATETIME, ts TIMESTAMP);
+INSERT INTO t1 VALUES('2011-01-06 12:34:30', '2011-01-06 12:34:30');
+SELECT MAX(dt), MAX(ts) FROM t1;
+SELECT MAX(ts) < '2010-01-01 00:00:00' FROM t1;
+SELECT MAX(dt) < '2010-01-01 00:00:00' FROM t1;
+SELECT MAX(ts) > '2010-01-01 00:00:00' FROM t1;
+SELECT MAX(dt) > '2010-01-01 00:00:00' FROM t1;
+SELECT MAX(ts) = '2011-01-06 12:34:30' FROM t1;
+SELECT MAX(dt) = '2011-01-06 12:34:30' FROM t1;
+DROP TABLE t1;
+
+--echo End of 5.5 tests
+

sql/item.cc

@@ -7370,8 +7370,7 @@ Item_cache* Item_cache::get_cache(const Item *item, const Item_result type)
     return new Item_cache_decimal();
   case STRING_RESULT:
     /* Not all functions that return DATE/TIME are actually DATE/TIME funcs. */
-    if ((item->field_type() == MYSQL_TYPE_DATE ||
-         item->field_type() == MYSQL_TYPE_DATETIME ||
+    if ((item->is_datetime() ||
          item->field_type() == MYSQL_TYPE_TIME) &&
         (const_cast<Item*>(item))->result_as_longlong())
       return new Item_cache_datetime(item->field_type());