Fixed bug#15950: NOW() optimized away in VIEWs

This bug is a side-effect of bug fix #16377. NOW() is optimized in
BETWEEN to integer constants to speed up query execution. When view is being
created it saves already modified query and thus becomes wrong.

The agg_cmp_type() function now substitutes constant result DATE/TIME functions 
for their results only if the current query isn't CREATE VIEW or SHOW CREATE
VIEW.

mysql-test/r/view.result

@@ -2850,3 +2850,10 @@ Tables_in_test
 t1
 DROP TABLE t1;
 DROP VIEW IF EXISTS v1;
+create table t1 (f1 datetime);
+create view v1 as select * from t1 where f1 between now() and now() + interval 1 minute;
+show create view v1;
+View	Create View
+v1	CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `v1` AS select `t1`.`f1` AS `f1` from `t1` where (`t1`.`f1` between now() and (now() + interval 1 minute))
+drop view v1;
+drop table t1;

mysql-test/t/view.test

@@ -2718,3 +2718,12 @@ DROP TABLE t1;
 --disable_warnings
 DROP VIEW IF EXISTS v1;
 --enable_warnings
+
+#
+# Bug #15950: NOW() optimized away in VIEWs
+#
+create table t1 (f1 datetime);
+create view v1 as select * from t1 where f1 between now() and now() + interval 1 minute;
+show create view v1;
+drop view v1;
+drop table t1;

sql/item_cmpfunc.cc

@@ -125,6 +125,13 @@ static void agg_cmp_type(THD *thd, Item_result *type, Item **items, uint nitems)
   uchar null_byte;
   Field *field= NULL;
 
+  /*
+    Do not convert items while creating a or showing a view in order
+    to store/display the original query in these cases.
+  */
+  if (thd->lex->sql_command != SQLCOM_CREATE_VIEW &&
+      thd->lex->sql_command != SQLCOM_SHOW_CREATE)
+  {
     /* Search for date/time fields/functions */
     for (i= 0; i < nitems; i++)
     {
@@ -152,6 +159,7 @@ static void agg_cmp_type(THD *thd, Item_result *type, Item **items, uint nitems)
         break;
       }
     }
+  }
   if (field)
   {
     /* Check the rest of the list for presence of a string field/function. */