Fixed bug #19490. The bug that caused server crash manifested

itself when executing queries referring to a view with GROUP BY
an expression containing non-constant interval.
It happened because Item_date_add_interval::eq neglected the
fact that the method can be applied to an expression of the form
    date(col) + interval time_to_sec(col) second
at the time when col could not be evaluated yet.
An attempt to evaluate time_to_sec(col) in this method resulted
in a crash.

mysql-test/r/view.result

@@ -2649,3 +2649,14 @@ ldt
 2006-01-01 03:00:00
 drop view v1, v2;
 drop table t1;
+CREATE TABLE t1 (id int NOT NULL PRIMARY KEY, d datetime);
+CREATE VIEW v1 AS
+SELECT id, date(d) + INTERVAL TIME_TO_SEC(d) SECOND AS t, COUNT(*)
+FROM t1 GROUP BY id, t;
+SHOW CREATE VIEW v1;
+View	Create View
+v1	CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `v1` AS select `t1`.`id` AS `id`,(cast(`t1`.`d` as date) + interval time_to_sec(`t1`.`d`) second) AS `t`,count(0) AS `COUNT(*)` from `t1` group by `t1`.`id`,(cast(`t1`.`d` as date) + interval time_to_sec(`t1`.`d`) second)
+SELECT * FROM v1;
+id	t	COUNT(*)
+DROP VIEW v1;
+DROP TABLE t1;

mysql-test/t/view.test

@@ -2512,3 +2512,19 @@ create view v2 as select convert_tz(dt, 'UTC', 'Europe/Moscow') as ldt from v1;
 select * from v2;
 drop view v1, v2;
 drop table t1;
+
+#
+# Bug #19490: usage of view specified by a query with GROUP BY
+#             an expression containing non-constant interval
+
+CREATE TABLE t1 (id int NOT NULL PRIMARY KEY, d datetime);
+
+CREATE VIEW v1 AS
+SELECT id, date(d) + INTERVAL TIME_TO_SEC(d) SECOND AS t, COUNT(*)
+  FROM t1 GROUP BY id, t;
+
+SHOW CREATE VIEW v1;
+SELECT * FROM v1;
+
+DROP VIEW v1;
+DROP TABLE t1;

sql/item_timefunc.cc

@@ -2144,8 +2144,13 @@ bool Item_date_add_interval::eq(const Item *item, bool binary_cmp) const
   Item_date_add_interval *other= (Item_date_add_interval*) item;
 
   if ((int_type != other->int_type) ||
-      (!args[0]->eq(other->args[0], binary_cmp)) ||
-      (get_interval_value(args[1], int_type, &val, &interval)))
+      (!args[0]->eq(other->args[0], binary_cmp)))
+    return FALSE;
+
+  if (!args[1]->const_item() || !other->args[1]->const_item())
+    return (args[1]->eq(other->args[1], binary_cmp)); 
+
+  if (get_interval_value(args[1], int_type, &val, &interval))
     return FALSE;
 
   val= other->value;