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Diffstat (limited to 'activerecord/lib/active_record/identity_map.rb')
-rw-r--r-- | activerecord/lib/active_record/identity_map.rb | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/identity_map.rb b/activerecord/lib/active_record/identity_map.rb new file mode 100644 index 0000000000..6718a92e13 --- /dev/null +++ b/activerecord/lib/active_record/identity_map.rb @@ -0,0 +1,104 @@ +module ActiveRecord + # = Active Record Identity Map + # + # Ensures that each object gets loaded only once by keeping every loaded + # object in a map. Looks up objects using the map when referring to them. + # + # More information on Identity Map pattern: + # http://www.martinfowler.com/eaaCatalog/identityMap.html + # + # == Configuration + # + # In order to enable IdentityMap, set <tt>config.active_record.identity_map = true</tt> + # in your <tt>config/application.rb</tt> file. + # + # IdentityMap is disabled by default. + # + module IdentityMap + extend ActiveSupport::Concern + + class << self + def enabled=(flag) + Thread.current[:identity_map_enabled] = flag + end + + def enabled + Thread.current[:identity_map_enabled] + end + alias enabled? enabled + + def repository + Thread.current[:identity_map] ||= Hash.new { |h,k| h[k] = {} } + end + + def use + old, self.enabled = enabled, true + + yield if block_given? + ensure + self.enabled = old + clear + end + + def without + old, self.enabled = enabled, false + + yield if block_given? + ensure + self.enabled = old + end + + def get(klass, primary_key) + obj = repository[klass.symbolized_base_class][primary_key] + obj.is_a?(klass) ? obj : nil + end + + def add(record) + repository[record.class.symbolized_base_class][record.id] = record + end + + def remove(record) + repository[record.class.symbolized_base_class].delete(record.id) + end + + def remove_by_id(symbolized_base_class, id) + repository[symbolized_base_class].delete(id) + end + + def clear + repository.clear + end + end + + module InstanceMethods + # Reinitialize an Identity Map model object from +coder+. + # +coder+ must contain the attributes necessary for initializing an empty + # model object. + def reinit_with(coder) + @attributes_cache = {} + dirty = @changed_attributes.keys + @attributes.update(coder['attributes'].except(*dirty)) + @changed_attributes.update(coder['attributes'].slice(*dirty)) + @changed_attributes.delete_if{|k,v| v.eql? @attributes[k]} + + set_serialized_attributes + + run_callbacks :find + + self + end + end + + class Middleware + def initialize(app) + @app = app + end + + def call(env) + ActiveRecord::IdentityMap.use do + @app.call(env) + end + end + end + end +end |