Update ClusterableModel.serializable_data() to support the exclude_fi…

…elds argument and support '__' in exclude_fields to control the representation of child items

modelcluster/models.py

@@ -232,23 +232,30 @@ def save(self, **kwargs):
         for field in m2m_fields_to_commit:
             getattr(self, field).commit()
 
-    def serializable_data(self):
-        obj = get_serializable_data_for_fields(self)
+    def serializable_data(self, exclude_fields=None):
+        obj = get_serializable_data_for_fields(self, exclude_fields=exclude_fields)
+
+        # normalize exclude_fields to a set
+        exclude = set(exclude_fields or ())
 
         for rel in get_all_child_relations(self):
             rel_name = rel.get_accessor_name()
-            children = getattr(self, rel_name).all()
+            if rel_name in exclude:
+                continue
 
+            # define a subset of exclude_fields for this relationship
+            rel_exclude = {f[len(rel_name) + 2:] for f in exclude if f.startswith(rel_name + '__')}
+
+            # serialize children to a list, using only the fields we need
+            children = getattr(self, rel_name).all().defer(*rel_exclude).iterator()
             if hasattr(rel.related_model, 'serializable_data'):
-                obj[rel_name] = [child.serializable_data() for child in children]
+                obj[rel_name] = [child.serializable_data(exclude_fields=rel_exclude) for child in children]
             else:
-                obj[rel_name] = [get_serializable_data_for_fields(child) for child in children]
+                obj[rel_name] = [get_serializable_data_for_fields(child, exclude_fields=rel_exclude) for child in children]
 
         for field in get_all_child_m2m_relations(self):
-            if field.serialize:
-                children = getattr(self, field.name).all()
-                obj[field.name] = [child.pk for child in children]
-
+            if field.serialize and field.name not in exclude:
+                obj[field.name] = list(getattr(self, field.name).all().values_list('pk', flat=True))
         return obj
 
     def to_json(self):