make the object column optional

CHANGELOG.md

@@ -11,7 +11,9 @@ recommendations of [keepachangelog.com](http://keepachangelog.com/).
 
 ### Added
 
-- None
+- [#1099](https://github.com/paper-trail-gem/paper_trail/issues/1099) -
+  Ability to save ~50% storage space by making the `object` column optional.
+  Note that this disables `reify` and `where_object`.
 
 ### Fixed
 

README.md

@@ -1212,6 +1212,12 @@ A valid adapter is a class that contains the following methods:
 
 For an example of such an implementation, see [paper_trail-hashdiff](https://github.com/hashwin/paper_trail-hashdiff)
 
+### 6.d. Excluding the Object Column
+
+The `object` column ends up storing a lot of duplicate data if you have models that have many columns,
+and that are updated many times. You can save ~50% of storage space by removing the column from the
+versions table. It's important to note that this will disable `reify` and `where_object`.
+
 ## 7. Testing
 
 You may want to turn PaperTrail off to speed up your tests.  See [Turning

lib/paper_trail/events/base.rb

@@ -254,6 +254,13 @@ def record_object_changes?
           @record.class.paper_trail.version_class.column_names.include?("object_changes")
       end
 
+      # Returns a boolean indicating whether to store the original object during save.
+      #
+      # @api private
+      def record_object?
+        @record.class.paper_trail.version_class.column_names.include?("object")
+      end
+
       # Returns an object which can be assigned to the `object` attribute of a
       # nascent version record. If the `object` column is a postgres `json`
       # column, then a hash can be used in the assignment, otherwise the column

lib/paper_trail/events/destroy.rb

@@ -16,9 +16,11 @@ def data
           item_id: @record.id,
           item_type: @record.class.base_class.name,
           event: @record.paper_trail_event || "destroy",
-          object: recordable_object(false),
           whodunnit: PaperTrail.request.whodunnit
         }
+        if record_object?
+          data[:object] = recordable_object(false)
+        end
         merge_metadata_into(data)
       end
     end

lib/paper_trail/events/update.rb

@@ -27,12 +27,14 @@ def initialize(record, in_after_callback, is_touch, force_changes)
       def data
         data = {
           event: @record.paper_trail_event || "update",
-          object: recordable_object(@is_touch),
           whodunnit: PaperTrail.request.whodunnit
         }
         if @record.respond_to?(:updated_at)
           data[:created_at] = @record.updated_at
         end
+        if record_object?
+          data[:object] = recordable_object(@is_touch)
+        end
         if record_object_changes?
           data[:object_changes] = recordable_object_changes(@changes)
         end

lib/paper_trail/queries/versions/where_object.rb

@@ -18,7 +18,10 @@ def initialize(version_model_class, attributes)
 
         # @api private
         def execute
-          case @version_model_class.columns_hash["object"].type
+          column = @version_model_class.columns_hash["object"]
+          fail "where_object can't be called without an object column" unless column
+
+          case column.type
           when :jsonb
             jsonb
           when :json

lib/paper_trail/version_concern.rb

@@ -205,6 +205,9 @@ def object_deserialized
     #   - `:preserve` - Attributes undefined in version record are not modified.
     #
     def reify(options = {})
+      unless self.class.column_names.include? "object"
+        fail "reify can't be called without an object column"
+      end
       return nil if object.nil?
       ::PaperTrail::Reifier.reify(self, options)
     end

spec/paper_trail/model_spec.rb

@@ -877,4 +877,50 @@
       expect(widget.versions.empty?).to(eq(true))
     end
   end
+
+  context "without the object column" do
+    before :all do
+      ActiveRecord::Migration.remove_column :versions, :object
+      PaperTrail::Version.reset_column_information
+    end
+    after :all do
+      ActiveRecord::Migration.add_column :versions, :object, :text
+      PaperTrail::Version.reset_column_information
+    end
+
+    it "versions are created" do
+      song = Song.create(length: 4)
+      version = song.versions.last.attributes
+      expect(version).to_not include 'object'
+      expect(version).to match hash_including 'event' => 'create', 'object_changes' => start_with('---')
+
+      song.update length: 5
+      version = song.versions.last.attributes
+      expect(version).to_not include 'object'
+      expect(version).to match hash_including 'event' => 'update', 'object_changes' => start_with('---')
+
+      song.destroy
+      version = song.versions.last.attributes
+      expect(version).to_not include 'object'
+      expect(version).to match hash_including 'event' => 'destroy', 'object_changes' => nil
+    end
+
+    it "reify doesn't work" do
+      song = Song.create(length: 4)
+      song.update length: 5
+
+      expect do
+        song.versions.first.reify
+      end.to raise_error "reify can't be called without an object column"
+    end
+
+    it "where_object doesn't work" do
+      song = Song.create(length: 4)
+      song.update length: 5
+
+      expect do
+        song.versions.where_object length: 4
+      end.to raise_error "where_object can't be called without an object column"
+    end
+  end
 end