Optimize post-rollback association reset

[Fixes #715]

CHANGELOG.md

@@ -22,6 +22,8 @@
 
 ### Fixed
 
+- [#715](https://github.com/airblade/paper_trail/issues/715) -
+  Optimize post-rollback association reset.
 - [#701](https://github.com/airblade/paper_trail/pull/701) /
   [#699](https://github.com/airblade/paper_trail/issues/699) -
   Cleaning old versions explicitly preserves the most recent

lib/paper_trail/has_paper_trail.rb

@@ -195,9 +195,11 @@ module PaperTrail
       end
 
       # Invoked after rollbacks to ensure versions records are not created
-      # for changes that never actually took place
+      # for changes that never actually took place.
+      # Optimization: Use lazy `reset` instead of eager `reload` because, in
+      # many use cases, the association will not be used.
       def clear_rolled_back_versions
-        send(self.class.versions_association_name).reload
+        send(self.class.versions_association_name).reset
       end
 
       # Returns the object (not a Version) as it was at the given timestamp.

spec/models/widget_spec.rb

@@ -110,6 +110,10 @@ describe Widget, type: :model do
           expect(changeset.fetch("name", [])).to_not include(rolled_back_name)
         end
       end
+
+      it "has not yet loaded the assocation" do
+        expect(widget.versions).to_not be_loaded
+      end
     end
   end