Bug#28450: The Item_date_add_interval in select list may fail the field

type assertion.

The bug was introduced by the patch for bug #16377.
The "+ INTERVAL" (Item_date_add_interval) function detects its result type
by the type of its first argument. But in some cases it returns STRING
as the result type. This happens when, for example, the first argument is a 
DATE represented as string. All this makes the get_datetime_value()
function misinterpret such result and return wrong DATE/DATETIME value.
To avoid such cases in the fix for #16377 the code that detects correct result
field type on the first execution was added to the
Item_date_add_interval::get_date() function. Due to this the result
field type of the Item_date_add_interval item stored by the send_fields()
function differs from item's result field type at the moment when
the item is actually sent. It causes an assertion failure.

Now the get_datetime_value() detects that the DATE value is returned by
some item not only by checking the result field type but also by comparing
the returned value with the 100000000L constant - any DATE value should be
less than this value.
Removed result field type adjusting code from the
Item_date_add_interval::get_date() function.

mysql-test/r/func_date_add.result

@@ -84,4 +84,15 @@ CAST('2006-09-26' AS DATE) + INTERVAL 1 YEAR
 SELECT CAST('2006-09-26' AS DATE) + INTERVAL 1 WEEK;
 CAST('2006-09-26' AS DATE) + INTERVAL 1 WEEK
 2006-10-03
+create table t1 (a int, b varchar(10));
+insert into t1 values (1, '2001-01-01'),(2, '2002-02-02');
+select '2007-01-01' + interval a day from t1;
+'2007-01-01' + interval a day
+2007-01-02
+2007-01-03
+select b + interval a day from t1;
+b + interval a day
+2001-01-02
+2002-02-04
+drop table t1;
 End of 5.0 tests

mysql-test/t/func_date_add.test

@@ -77,4 +77,14 @@ SELECT CAST('2006-09-26' AS DATE) + INTERVAL 1 MONTH;
 SELECT CAST('2006-09-26' AS DATE) + INTERVAL 1 YEAR;
 SELECT CAST('2006-09-26' AS DATE) + INTERVAL 1 WEEK;
 
+#
+# Bug#28450: The Item_date_add_interval in select list may fail the field 
+#            type assertion.
+#
+create table t1 (a int, b varchar(10));
+insert into t1 values (1, '2001-01-01'),(2, '2002-02-02'); 
+select '2007-01-01' + interval a day from t1;
+select b + interval a day from t1;
+drop table t1;
+
 --echo End of 5.0 tests

sql/item_cmpfunc.cc

@@ -766,7 +766,12 @@ get_datetime_value(THD *thd, Item ***item_arg, Item **cache_arg,
   {
     value= item->val_int();
     *is_null= item->null_value;
-    if (item->field_type() == MYSQL_TYPE_DATE)
+    /*
+      Item_date_add_interval may return MYSQL_TYPE_STRING as the result
+      field type. To detect that the DATE value has been returned we
+      compare it with 1000000L - any DATE value should be less than it.
+    */
+    if (item->field_type() == MYSQL_TYPE_DATE || value < 100000000L)
       value*= 1000000L;
   }
   else

sql/item_timefunc.cc

@@ -2180,27 +2180,6 @@ bool Item_date_add_interval::get_date(MYSQL_TIME *ltime, uint fuzzy_date)
   default:
     goto null_date;
   }
-
-  /* Adjust cached_field_type according to the detected type. */
-  if (cached_field_type == MYSQL_TYPE_STRING)
-  {
-    switch (ltime->time_type)
-    {
-    case MYSQL_TIMESTAMP_DATE:
-      cached_field_type= MYSQL_TYPE_DATE;
-      break;
-    case MYSQL_TIMESTAMP_DATETIME:
-      cached_field_type= MYSQL_TYPE_DATETIME;
-      break;
-    case MYSQL_TIMESTAMP_TIME:
-      cached_field_type= MYSQL_TYPE_TIME;
-      break;
-    default:
-      /* Shouldn't get here. */
-      DBUG_ASSERT(0);
-      break;
-    }
-  }
   return 0;					// Ok
 
 invalid_date: