Add version limit config option. Close #213

CHANGELOG.md

@@ -4,6 +4,8 @@
   so that `current_user` only gets invoked if it is defined.
   - [#219](https://github.com/airblade/paper_trail/pull/219) - Fixed issue where attributes stored with `nil` value might not get
   reified properly depending on the way the serializer worked.
+  - [#213](https://github.com/airblade/paper_trail/issues/213) - Added a `version_limit` option to the `PaperTrail::Config` options
+  that can be used to restrict the number of versions PaperTrail will store per object instance.
   - [#187](https://github.com/airblade/paper_trail/pull/187) - Confirmed JRuby support.
   - [#174](https://github.com/airblade/paper_trail/pull/174) - The `event` field on the versions table can now be customized.
 

README.md

@@ -771,6 +771,17 @@ A valid serializer is a `module` (or `class`) that defines a `load` and `dump` m
 * [Yaml](https://github.com/airblade/paper_trail/blob/master/lib/paper_trail/serializers/yaml.rb) - Default
 * [Json](https://github.com/airblade/paper_trail/blob/master/lib/paper_trail/serializers/json.rb)
 
+## Limiting the number of versions created per object instance
+
+If you are weary of your `versions` table growing to an unwieldy size, or just don't care to track more than a certain number of versions about an object,
+there is a configuration option that can be set to cap the number of versions saved per object.  Note that if this value is set to a numeric value, the number
+version marking the `create` event will always be preserved, so it actually has a version limit of 1 higher than what this value is set to.
+
+```ruby
+>> PaperTrail.config.version_limit = 3 # will make it so that a maximum of 4 versions will be stored for each object (3 most recent ones plus a `create` event)
+>> PaperTrail.config.version_limit = nil # disables/removes the version limit
+```
+
 ## Deleting Old Versions
 
 Over time your `versions` table will grow to an unwieldy size.  Because each version is self-contained (see the Diffing section above for more) you can simply delete any records you don't want any more.  For example:

lib/paper_trail/config.rb

@@ -3,7 +3,7 @@ require 'singleton'
 module PaperTrail
   class Config
     include Singleton
-    attr_accessor :enabled, :timestamp_field, :serializer
+    attr_accessor :enabled, :timestamp_field, :serializer, :version_limit
 
     def initialize
       @enabled         = true # Indicates whether PaperTrail is on or off.

lib/paper_trail/version.rb

@@ -3,6 +3,8 @@ class Version < ActiveRecord::Base
   validates_presence_of :event
   attr_accessible :item_type, :item_id, :event, :whodunnit, :object, :object_changes
 
+  after_create :enforce_version_limit!
+
   def self.with_item_keys(item_type, item_id)
     where :item_type => item_type, :item_id => item_id
   end
@@ -19,6 +21,10 @@ class Version < ActiveRecord::Base
     where :event => 'destroy'
   end
 
+  def self.not_creates
+    where 'event <> ?', 'create'
+  end
+
   scope :subsequent, lambda { |version|
     where("#{self.primary_key} > ?", version).order("#{self.primary_key} ASC")
   }
@@ -180,4 +186,13 @@ class Version < ActiveRecord::Base
     end
   end
 
+  # checks to see if a value has been set for the `version_limit` config option, and if so enforces it
+  def enforce_version_limit!
+    return unless PaperTrail.config.version_limit.is_a? Numeric
+    previous_versions = sibling_versions.not_creates
+    return unless previous_versions.size > PaperTrail.config.version_limit
+    excess_previous_versions = previous_versions - previous_versions.last(PaperTrail.config.version_limit)
+    excess_previous_versions.map(&:destroy)
+  end
+
 end

test/unit/model_test.rb

@@ -1266,6 +1266,22 @@ class HasPaperTrailModelTest < ActiveSupport::TestCase
     end
   end
 
+  context '`PaperTrail::Config.version_limit` set' do
+    setup do
+      PaperTrail.config.version_limit = 2
+      @widget = Widget.create! :name => 'Henry'
+      6.times { @widget.update_attribute(:name, Faker::Lorem.word) }
+    end
+
+    teardown { PaperTrail.config.version_limit = nil }
+
+    should "limit the number of versions to 3 (2 plus the created at event)" do
+      assert_equal 'create', @widget.versions.first.event
+      assert_equal 3, @widget.versions.size
+    end
+  end
+
+
   private
 
   # Updates `model`'s last version so it looks like the version was

test/unit/version_test.rb

@@ -40,4 +40,18 @@ class VersionTest < ActiveSupport::TestCase
       end
     end
   end
+
+  context "Version.not_creates" do
+    setup {
+      @article.update_attributes(:name => 'Animal')
+      @article.destroy
+      assert Version.not_creates.present?
+    }
+
+    should "return all items except create events" do
+      Version.not_creates.each do |version|
+        assert_not_equal "create", version.event
+      end
+    end
+  end
 end