New parameter 'no_read=True' for sync() operation

CHANGES.rst

@@ -1,6 +1,12 @@
 Changelog
 =========
 
+0.5.0
+-----
+* **Breakage**: Removing support for overflow fields. The only fields flywheel will care about now are those that are explicitly set as a Field()
+* Flywheel no longer forces raise_on_conflict to be True when you sync changes to fields that are part of a composite field. It is now up to the user to avoid putting their composite fields into an inconsistent state.
+* Feature: sync() has a new argument, ``no_read``, which changes the behavior for syncing models with no changes. Instead of performing a GET, it will leave them as-is. This should make it easer to perform batch syncs without worrying as much about wasted bandwidth on GETs. 
+
 0.4.3
 -----
 * Bug fix: Incorrect ``ConditionalCheckFailedException`` when syncing changes to a Composite field.

flywheel/engine.py

@@ -495,7 +495,8 @@ def refresh(self, items, consistent=False):
                     for key, val in data.items():
                         item.set_ddb_val_(key, val)
 
-    def sync(self, items, raise_on_conflict=None, consistent=False, constraints=None):
+    def sync(self, items, raise_on_conflict=None, consistent=False,
+             constraints=None, no_read=False):
         """
         Sync model changes back to database
 
@@ -517,11 +518,14 @@ def sync(self, items, raise_on_conflict=None, consistent=False, constraints=None
             List of more complex constraints that must pass for the update to
             complete. Must be used with raise_on_conflict=True. Format is the
             same as query filters (e.g. Model.fieldname > 5)
+        no_read : bool, optional
+            If True, don't perform a GET on models with no changes. (default False)
 
         Raises
         ------
         exc : :class:`dynamo3.CheckFailed`
-            If raise_on_conflict=True and the model changed underneath us
+            If raise_on_conflict=True and the data in dynamo fails the
+            contraint checks.
 
         """
         if raise_on_conflict is None:
@@ -600,4 +604,5 @@ def sync(self, items, raise_on_conflict=None, consistent=False, constraints=None
                 except CheckFailed:
                     pass
         # Refresh item data
-        self.refresh(refresh_models, consistent=consistent)
+        if not no_read:
+            self.refresh(refresh_models, consistent=consistent)

flywheel/models.py

@@ -143,19 +143,18 @@ def refresh(self, consistent=False):
 
         self.__engine__.refresh(self, consistent=consistent)
 
-    def sync(self, raise_on_conflict=None, constraints=None):
+    def sync(self, *args, **kwargs):
         """ Sync model changes back to database """
         if self.__engine__ is None:
             raise ValueError("Cannot sync: No DB connection")
 
-        self.__engine__.sync(self, raise_on_conflict=raise_on_conflict,
-                             constraints=constraints)
+        self.__engine__.sync(self, *args, **kwargs)
 
-    def delete(self, raise_on_conflict=None):
+    def delete(self, *args, **kwargs):
         """ Delete the model from the database """
         if self.__engine__ is None:
             raise ValueError("Cannot delete: No DB connection")
-        self.__engine__.delete(self, raise_on_conflict=raise_on_conflict)
+        self.__engine__.delete(self, *args, **kwargs)
 
     @classmethod
     def __on_create__(cls):

tests/test_models.py

@@ -646,6 +646,26 @@ def test_delattr_private_field(self):
         del a._foobar
         self.assertFalse(hasattr(a, '_foobar'))
 
+    def test_sync_refresh(self):
+        """ Syncing a model with no changes will refresh the data """
+        a = Article(text='foo')
+        self.engine.save(a)
+        a2 = self.engine.scan(Article).first()
+        a2.text = 'bar'
+        self.engine.sync(a2)
+        a.sync()
+        self.assertEqual(a.text, 'bar')
+
+    def test_sync_no_read(self):
+        """ Sync(no_read=True) performs a write and no reads """
+        a = Article(text='foo')
+        self.engine.save(a)
+        a2 = self.engine.scan(Article).first()
+        a2.text = 'bar'
+        self.engine.sync(a2)
+        a.sync(no_read=True)
+        self.assertEqual(a.text, 'foo')
+
 
 class Store(Model):