If fire_delta? exists in the model, let it decide.

Overriding should_toggle_delta? or indexed_data_changed? isn't an option, because those methods are loaded only when the index definitions are (and thus would actually override custom versions). This allows us some way to delegate the decision.

lib/thinking_sphinx/active_record/delta.rb

@@ -3,7 +3,7 @@ module ActiveRecord
     # This module contains all the delta-related code for models. There isn't
     # really anything you need to call manually in here - except perhaps
     # index_delta, but not sure what reason why.
-    # 
+    #
     module Delta
       # Code for after_commit callback is written by Eli Miller:
       # http://elimiller.blogspot.com/2007/06/proper-cache-expiry-with-aftercommit.html
@@ -18,38 +18,40 @@ class << self
             def index_delta(instance = nil)
               delta_objects.each { |obj| obj.index(self, instance) }
             end
-            
+
             def delta_objects
               self.sphinx_indexes.collect(&:delta_object).compact
             end
           end
-          
+
           def toggled_delta?
             self.class.delta_objects.any? { |obj| obj.toggled(self) }
           end
-          
+
           private
-          
+
           # Set the delta value for the model to be true.
           def toggle_delta
             self.class.delta_objects.each { |obj|
               obj.toggle(self)
             } if should_toggle_delta?
           end
-          
+
           # Build the delta index for the related model. This won't be called
           # if running in the test environment.
-          # 
+          #
           def index_delta
             self.class.index_delta(self) if self.class.delta_objects.any? { |obj|
               obj.toggled(self)
             }
           end
-          
+
           def should_toggle_delta?
+            return fire_delta? if respond_to?(:fire_delta?)
+
             self.new_record? || indexed_data_changed?
           end
-          
+
           def indexed_data_changed?
             sphinx_indexes.any? { |index|
               index.fields.any? { |field| field.changed?(self) } ||