Merge pull request #5261 from carlosantoniodasilva/identity-map-removal

Remove IdentityMap

34 files changed, 49 insertions, 966 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 6fd86b1f32..5a289a5aac 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,16 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Remove IdentityMap
+
+    IdentityMap has never graduated to be an "enabled-by-default" feature, due
+    to some inconsistencies with associations, as described in this commit:
+
+       https://github.com/rails/rails/commit/302c912bf6bcd0fa200d964ec2dc4a44abe328a6
+
+    Hence the removal from the codebase, until such issues are fixed.
+
+    *Carlos Antonio da Silva*
+
 *   Added the schema cache dump feature.
 
     `Schema cache dump` feature was implemetend. This feature can dump/load internal state of `SchemaCache` instance
diff --git a/activerecord/RUNNING_UNIT_TESTS b/activerecord/RUNNING_UNIT_TESTS
index a1ed6712c5..2c310e7ac3 100644
--- a/activerecord/RUNNING_UNIT_TESTS
+++ b/activerecord/RUNNING_UNIT_TESTS
@@ -26,13 +26,6 @@ You can run all the tests for a given database via rake:
 
 The 'rake test' task will run all the tests for mysql, mysql2, sqlite3 and postgresql.
 
-== Identity Map
-
-By default the tests run with the Identity Map turned off. But all tests should pass whether or
-not the identity map is on or off. You can turn it on using the IM env variable:
-
-  $ IM=true ruby -Itest test/case/base_test.rb
-
 == Config file
 
 By default, the config file is expected to be at the path test/config.yml. You can specify a
diff --git a/activerecord/lib/active_record.rb b/activerecord/lib/active_record.rb
index 73c8a06ab7..0cb0644bcf 100644
--- a/activerecord/lib/active_record.rb
+++ b/activerecord/lib/active_record.rb
@@ -65,7 +65,6 @@ module ActiveRecord
     autoload :DynamicFinderMatch
     autoload :DynamicScopeMatch
     autoload :Explain
-    autoload :IdentityMap
     autoload :Inheritance
     autoload :Integration
     autoload :Migration
diff --git a/activerecord/lib/active_record/associations/association.rb b/activerecord/lib/active_record/associations/association.rb
index 512c52338e..fb0ca15c23 100644
--- a/activerecord/lib/active_record/associations/association.rb
+++ b/activerecord/lib/active_record/associations/association.rb
@@ -45,7 +45,6 @@ module ActiveRecord
       # Resets the \loaded flag to +false+ and sets the \target to +nil+.
       def reset
         @loaded = false
-        IdentityMap.remove(target) if IdentityMap.enabled? && target
         @target = nil
       end
 
@@ -135,17 +134,7 @@ module ActiveRecord
       # ActiveRecord::RecordNotFound is rescued within the method, and it is
       # not reraised. The proxy is \reset and +nil+ is the return value.
       def load_target
-        if find_target?
-          begin
-            if IdentityMap.enabled? && association_class && association_class.respond_to?(:base_class)
-              @target = IdentityMap.get(association_class, owner[reflection.foreign_key])
-            end
-          rescue NameError
-            nil
-          ensure
-            @target ||= find_target
-          end
-        end
+        @target ||= find_target if find_target?
         loaded! unless loaded?
         target
       rescue ActiveRecord::RecordNotFound
diff --git a/activerecord/lib/active_record/attribute_methods/dirty.rb b/activerecord/lib/active_record/attribute_methods/dirty.rb
index 3a737e5b35..11c63591e3 100644
--- a/activerecord/lib/active_record/attribute_methods/dirty.rb
+++ b/activerecord/lib/active_record/attribute_methods/dirty.rb
@@ -22,8 +22,6 @@ module ActiveRecord
         if status = super
           @previously_changed = changes
           @changed_attributes.clear
-        elsif IdentityMap.enabled?
-          IdentityMap.remove(self)
         end
         status
       end
@@ -34,9 +32,6 @@ module ActiveRecord
           @previously_changed = changes
           @changed_attributes.clear
         end
-      rescue
-        IdentityMap.remove(self) if IdentityMap.enabled?
-        raise
       end
 
       # <tt>reload</tt> the record and clears changed attributes.
diff --git a/activerecord/lib/active_record/autosave_association.rb b/activerecord/lib/active_record/autosave_association.rb
index eb3ae7014e..be0af081d1 100644
--- a/activerecord/lib/active_record/autosave_association.rb
+++ b/activerecord/lib/active_record/autosave_association.rb
@@ -328,7 +328,6 @@ module ActiveRecord
         autosave = reflection.options[:autosave]
 
         if records = associated_records_to_validate_or_save(association, @new_record_before_save, autosave)
-          begin
           records.each do |record|
             next if record.destroyed?
 
@@ -348,11 +347,6 @@ module ActiveRecord
 
             raise ActiveRecord::Rollback unless saved
           end
-          rescue
-            records.each {|x| IdentityMap.remove(x) } if IdentityMap.enabled?
-            raise
-          end
-
         end
 
         # reconstruct the scope now that we know the owner's id
diff --git a/activerecord/lib/active_record/counter_cache.rb b/activerecord/lib/active_record/counter_cache.rb
index 8d5388e1f3..f52979ebd9 100644
--- a/activerecord/lib/active_record/counter_cache.rb
+++ b/activerecord/lib/active_record/counter_cache.rb
@@ -69,8 +69,6 @@ module ActiveRecord
         "#{quoted_column} = COALESCE(#{quoted_column}, 0) #{operator} #{value.abs}"
       end
 
-      IdentityMap.remove_by_id(symbolized_base_class, id) if IdentityMap.enabled?
-
       update_all(updates.join(', '), primary_key => id)
     end
 
diff --git a/activerecord/lib/active_record/fixtures.rb b/activerecord/lib/active_record/fixtures.rb
index b82d5b5621..5c42e8f719 100644
--- a/activerecord/lib/active_record/fixtures.rb
+++ b/activerecord/lib/active_record/fixtures.rb
@@ -796,9 +796,7 @@ module ActiveRecord
                 @fixture_cache[fixture_name].delete(fixture) if force_reload
 
                 if @loaded_fixtures[fixture_name][fixture.to_s]
-                  ActiveRecord::IdentityMap.without do
-                    @fixture_cache[fixture_name][fixture] ||= @loaded_fixtures[fixture_name][fixture.to_s].find
-                  end
+                  @fixture_cache[fixture_name][fixture] ||= @loaded_fixtures[fixture_name][fixture.to_s].find
                 else
                   raise StandardError, "No entry named '#{fixture}' found for fixture collection '#{fixture_name}'"
                 end
diff --git a/activerecord/lib/active_record/identity_map.rb b/activerecord/lib/active_record/identity_map.rb
deleted file mode 100644
index d9777bb2f6..0000000000
--- a/activerecord/lib/active_record/identity_map.rb
+++ /dev/null
@@ -1,144 +0,0 @@
-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 and still in development (i.e. use it with care).
-  #
-  # == Associations
-  #
-  # Active Record Identity Map does not track associations yet. For example:
-  #
-  #   comment = @post.comments.first
-  #   comment.post = nil
-  #   @post.comments.include?(comment) #=> true
-  #
-  # Ideally, the example above would return false, removing the comment object from the
-  # post association when the association is nullified. This may cause side effects, as
-  # in the situation below, if Identity Map is enabled:
-  #
-  #   Post.has_many :comments, :dependent => :destroy
-  #
-  #   comment = @post.comments.first
-  #   comment.post = nil
-  #   comment.save
-  #   Post.destroy(@post.id)
-  #
-  # Without using Identity Map, the code above will destroy the @post object leaving
-  # the comment object intact. However, once we enable Identity Map, the post loaded
-  # by Post.destroy is exactly the same object as the object @post. As the object @post
-  # still has the comment object in @post.comments, once Identity Map is enabled, the
-  # comment object will be accidently removed.
-  #
-  # This inconsistency is meant to be fixed in future Rails releases.
-  #
-  module IdentityMap
-
-    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)
-        record = repository[klass.symbolized_sti_name][primary_key]
-
-        if record.is_a?(klass)
-          ActiveSupport::Notifications.instrument("identity.active_record",
-            :line => "From Identity Map (id: #{primary_key})",
-            :name => "#{klass} Loaded",
-            :connection_id => object_id)
-
-          record
-        else
-          nil
-        end
-      end
-
-      def add(record)
-        repository[record.class.symbolized_sti_name][record.id] = record
-      end
-
-      def remove(record)
-        repository[record.class.symbolized_sti_name].delete(record.id)
-      end
-
-      def remove_by_id(symbolized_sti_name, id)
-        repository[symbolized_sti_name].delete(id)
-      end
-
-      def clear
-        repository.clear
-      end
-    end
-
-    # 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 = self.class.initialize_attributes(coder['attributes'].except(*dirty))
-      @attributes.update(attributes)
-      @changed_attributes.update(coder['attributes'].slice(*dirty))
-      @changed_attributes.delete_if{|k,v| v.eql? @attributes[k]}
-
-      run_callbacks :find
-
-      self
-    end
-
-    class Middleware
-      def initialize(app)
-        @app = app
-      end
-
-      def call(env)
-        enabled = IdentityMap.enabled
-        IdentityMap.enabled = true
-
-        response = @app.call(env)
-        response[2] = Rack::BodyProxy.new(response[2]) do
-          IdentityMap.enabled = enabled
-          IdentityMap.clear
-        end
-
-        response
-      end
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/inheritance.rb b/activerecord/lib/active_record/inheritance.rb
index 2c766411a0..ebe244c6a6 100644
--- a/activerecord/lib/active_record/inheritance.rb
+++ b/activerecord/lib/active_record/inheritance.rb
@@ -63,26 +63,9 @@ module ActiveRecord
       # single-table inheritance model that makes it possible to create
       # objects of different types from the same table.
       def instantiate(record, column_types = {})
-        sti_class = find_sti_class(record[inheritance_column])
-        record_id = sti_class.primary_key && record[sti_class.primary_key]
-
-        if ActiveRecord::IdentityMap.enabled? && record_id
-          if (column = sti_class.columns_hash[sti_class.primary_key]) && column.number?
-            record_id = record_id.to_i
-          end
-          if instance = IdentityMap.get(sti_class, record_id)
-            instance.reinit_with('attributes' => record)
-          else
-            instance = sti_class.allocate.init_with('attributes' => record)
-            IdentityMap.add(instance)
-          end
-        else
-          column_types = sti_class.decorate_columns(column_types)
-          instance = sti_class.allocate.init_with('attributes' => record,
-                                                  'column_types' => column_types)
-        end
-
-        instance
+        sti_class    = find_sti_class(record[inheritance_column])
+        column_types = sti_class.decorate_columns(column_types)
+        sti_class.allocate.init_with('attributes' => record, 'column_types' => column_types)
       end
 
       # For internal use.
diff --git a/activerecord/lib/active_record/model.rb b/activerecord/lib/active_record/model.rb
index 86de5ab2fa..105d1e0e2b 100644
--- a/activerecord/lib/active_record/model.rb
+++ b/activerecord/lib/active_record/model.rb
@@ -60,7 +60,6 @@ module ActiveRecord
     include AttributeMethods
     include Callbacks, ActiveModel::Observing, Timestamp
     include Associations
-    include IdentityMap
     include ActiveModel::SecurePassword
     include AutosaveAssociation, NestedAttributes
     include Aggregations, Transactions, Reflection, Serialization, Store
diff --git a/activerecord/lib/active_record/persistence.rb b/activerecord/lib/active_record/persistence.rb
index 09502bb52c..35c922e979 100644
--- a/activerecord/lib/active_record/persistence.rb
+++ b/activerecord/lib/active_record/persistence.rb
@@ -115,10 +115,7 @@ module ActiveRecord
     # callbacks, Observer methods, or any <tt>:dependent</tt> association
     # options, use <tt>#destroy</tt>.
     def delete
-      if persisted?
-        self.class.delete(id)
-        IdentityMap.remove(self) if IdentityMap.enabled?
-      end
+      self.class.delete(id) if persisted?
       @destroyed = true
       freeze
     end
@@ -129,7 +126,6 @@ module ActiveRecord
       destroy_associations
 
       if persisted?
-        IdentityMap.remove(self) if IdentityMap.enabled?
         pk         = self.class.primary_key
         column     = self.class.columns_hash[pk]
         substitute = connection.substitute_at(column, 0)
@@ -284,11 +280,9 @@ module ActiveRecord
       clear_aggregation_cache
       clear_association_cache
 
-      IdentityMap.without do
-        fresh_object = self.class.unscoped { self.class.find(id, options) }
-        @attributes.update(fresh_object.instance_variable_get('@attributes'))
-        @columns_hash = fresh_object.instance_variable_get('@columns_hash')
-      end
+      fresh_object = self.class.unscoped { self.class.find(id, options) }
+      @attributes.update(fresh_object.instance_variable_get('@attributes'))
+      @columns_hash = fresh_object.instance_variable_get('@columns_hash')
 
       @attributes_cache = {}
       self
@@ -363,10 +357,8 @@ module ActiveRecord
       attributes_values = arel_attributes_with_values_for_create(!id.nil?)
 
       new_id = self.class.unscoped.insert attributes_values
-
       self.id ||= new_id if self.class.primary_key
 
-      IdentityMap.add(self) if IdentityMap.enabled?
       @new_record = false
       id
     end
diff --git a/activerecord/lib/active_record/railtie.rb b/activerecord/lib/active_record/railtie.rb
index 516c450f85..ee3a6bf8c0 100644
--- a/activerecord/lib/active_record/railtie.rb
+++ b/activerecord/lib/active_record/railtie.rb
@@ -53,11 +53,6 @@ module ActiveRecord
       ActiveSupport.on_load(:active_record) { self.logger ||= ::Rails.logger }
     end
 
-    initializer "active_record.identity_map" do |app|
-      config.app_middleware.insert_after "::ActionDispatch::Callbacks",
-        "ActiveRecord::IdentityMap::Middleware" if config.active_record.delete(:identity_map)
-    end
-
     initializer "active_record.set_configs" do |app|
       ActiveSupport.on_load(:active_record) do
         if app.config.active_record.delete(:whitelist_attributes)
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 7531e1fe6f..6f39708ec3 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -168,13 +168,7 @@ module ActiveRecord
       default_scoped = with_default_scope
 
       if default_scoped.equal?(self)
-        @records = if @readonly_value.nil? && !@klass.locking_enabled?
-          eager_loading? ? find_with_associations : @klass.find_by_sql(arel, @bind_values)
-        else
-          IdentityMap.without do
-            eager_loading? ? find_with_associations : @klass.find_by_sql(arel, @bind_values)
-          end
-        end
+        @records = eager_loading? ? find_with_associations : @klass.find_by_sql(arel, @bind_values)
 
         preload = @preload_values
         preload +=  @includes_values unless eager_loading?
@@ -274,7 +268,6 @@ module ActiveRecord
     #   # The same idea applies to limit and order
     #   Book.where('title LIKE ?', '%Rails%').order(:created_at).limit(5).update_all(:author => 'David')
     def update_all(updates, conditions = nil, options = {})
-      IdentityMap.repository[symbolized_base_class].clear if IdentityMap.enabled?
       if conditions || options.present?
         where(conditions).apply_finder_options(options.slice(:limit, :order)).update_all(updates)
       else
@@ -404,7 +397,6 @@ module ActiveRecord
     # If you need to destroy dependent associations or call your <tt>before_*</tt> or
     # +after_destroy+ callbacks, use the +destroy_all+ method instead.
     def delete_all(conditions = nil)
-      IdentityMap.repository[symbolized_base_class] = {} if IdentityMap.enabled?
       if conditions
         where(conditions).delete_all
       else
@@ -437,7 +429,6 @@ module ActiveRecord
     #   # Delete multiple rows
     #   Todo.delete([2,3,4])
     def delete(id_or_array)
-      IdentityMap.remove_by_id(self.symbolized_base_class, id_or_array) if IdentityMap.enabled?
       where(primary_key => id_or_array).delete_all
     end
 
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index adfacf37ee..52e67ecc6e 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -318,17 +318,7 @@ module ActiveRecord
     def find_one(id)
       id = id.id if ActiveRecord::Base === id
 
-      if IdentityMap.enabled? && where_values.blank? &&
-        limit_value.blank? && order_values.blank? &&
-        includes_values.blank? && preload_values.blank? &&
-        readonly_value.nil? && joins_values.blank? &&
-        !@klass.locking_enabled? &&
-        record = IdentityMap.get(@klass, id)
-        return record
-      end
-
       column = columns_hash[primary_key]
-
       substitute = connection.substitute_at(column, @bind_values.length)
       relation = where(table[primary_key].eq(substitute))
       relation.bind_values += [[column, id]]
diff --git a/activerecord/lib/active_record/test_case.rb b/activerecord/lib/active_record/test_case.rb
index 4d881f0f7d..fcaa4b74a6 100644
--- a/activerecord/lib/active_record/test_case.rb
+++ b/activerecord/lib/active_record/test_case.rb
@@ -7,20 +7,10 @@ module ActiveRecord
   #
   # Defines some test assertions to test against SQL queries.
   class TestCase < ActiveSupport::TestCase #:nodoc:
-    setup :cleanup_identity_map
-
-    def setup
-      cleanup_identity_map
-    end
-
     def teardown
       SQLCounter.log.clear
     end
 
-    def cleanup_identity_map
-      ActiveRecord::IdentityMap.clear
-    end
-
     def assert_date_from_db(expected, actual, message = nil)
       # SybaseAdapter doesn't have a separate column type just for dates,
       # so the time is in the string and incorrectly formatted
diff --git a/activerecord/lib/active_record/transactions.rb b/activerecord/lib/active_record/transactions.rb
index b492377d18..743dfc5a38 100644
--- a/activerecord/lib/active_record/transactions.rb
+++ b/activerecord/lib/active_record/transactions.rb
@@ -251,7 +251,6 @@ module ActiveRecord
       remember_transaction_record_state
       yield
     rescue Exception
-      IdentityMap.remove(self) if IdentityMap.enabled?
       restore_transaction_record_state
       raise
     ensure
@@ -270,7 +269,6 @@ module ActiveRecord
     def rolledback!(force_restore_state = false) #:nodoc:
       run_callbacks :rollback
     ensure
-      IdentityMap.remove(self) if IdentityMap.enabled?
       restore_transaction_record_state(force_restore_state)
     end
 
diff --git a/activerecord/test/cases/associations/eager_load_includes_full_sti_class_test.rb b/activerecord/test/cases/associations/eager_load_includes_full_sti_class_test.rb
index 7965bb404c..3044a8c312 100644
--- a/activerecord/test/cases/associations/eager_load_includes_full_sti_class_test.rb
+++ b/activerecord/test/cases/associations/eager_load_includes_full_sti_class_test.rb
@@ -27,7 +27,6 @@ class EagerLoadIncludeFullStiClassNamesTest < ActiveRecord::TestCase
     post = Namespaced::Post.find_by_title( 'Great stuff', :include => :tagging )
     assert_nil post.tagging
 
-    ActiveRecord::IdentityMap.clear
     ActiveRecord::Base.store_full_sti_class = true
     post = Namespaced::Post.find_by_title( 'Great stuff', :include => :tagging )
     assert_instance_of Tagging, post.tagging
diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb
index b79c69bbb5..b27a93f857 100644
--- a/activerecord/test/cases/associations/eager_test.rb
+++ b/activerecord/test/cases/associations/eager_test.rb
@@ -197,7 +197,7 @@ class EagerAssociationTest < ActiveRecord::TestCase
     author = authors(:david)
     post = author.post_about_thinking_with_last_comment
     last_comment = post.last_comment
-    author = assert_queries(ActiveRecord::IdentityMap.enabled? ? 2 : 3) { Author.find(author.id, :include => {:post_about_thinking_with_last_comment => :last_comment})} # find the author, then find the posts, then find the comments
+    author = assert_queries(3) { Author.find(author.id, :include => {:post_about_thinking_with_last_comment => :last_comment})} # find the author, then find the posts, then find the comments
     assert_no_queries do
       assert_equal post, author.post_about_thinking_with_last_comment
       assert_equal last_comment, author.post_about_thinking_with_last_comment.last_comment
@@ -208,7 +208,7 @@ class EagerAssociationTest < ActiveRecord::TestCase
     post = posts(:welcome)
     author = post.author
     author_address = author.author_address
-    post = assert_queries(ActiveRecord::IdentityMap.enabled? ? 2 : 3) { Post.find(post.id, :include => {:author_with_address => :author_address}) } # find the post, then find the author, then find the address
+    post = assert_queries(3) { Post.find(post.id, :include => {:author_with_address => :author_address}) } # find the post, then find the author, then find the address
     assert_no_queries do
       assert_equal author, post.author_with_address
       assert_equal author_address, post.author_with_address.author_address
@@ -611,9 +611,9 @@ class EagerAssociationTest < ActiveRecord::TestCase
     assert posts[1].categories.include?(categories(:general))
   end
 
-  # This is only really relevant when the identity map is off. Since the preloader for habtm
-  # gets raw row hashes from the database and then instantiates them, this test ensures that
-  # it only instantiates one actual object per record from the database.
+  # Since the preloader for habtm gets raw row hashes from the database and then
+  # instantiates them, this test ensures that it only instantiates one actual
+  # object per record from the database.
   def test_has_and_belongs_to_many_should_not_instantiate_same_records_multiple_times
     welcome    = posts(:welcome)
     categories = Category.includes(:posts)
@@ -1002,18 +1002,18 @@ class EagerAssociationTest < ActiveRecord::TestCase
     assert_equal [posts(:welcome)], posts
     assert_equal authors(:david), assert_no_queries { posts[0].author}
 
-    posts = assert_queries(ActiveRecord::IdentityMap.enabled? ? 1 : 2) do
+    posts = assert_queries(2) do
       Post.find(:all, :select => 'distinct posts.*', :include => :author, :joins => [:comments], :conditions => "comments.body like 'Thank you%'", :order => 'posts.id')
     end
     assert_equal [posts(:welcome)], posts
     assert_equal authors(:david), assert_no_queries { posts[0].author}
 
-    posts = assert_queries(ActiveRecord::IdentityMap.enabled? ? 1 : 2) do
+    posts = assert_queries(2) do
       Post.find(:all, :include => :author, :joins => {:taggings => :tag}, :conditions => "tags.name = 'General'", :order => 'posts.id')
     end
     assert_equal posts(:welcome, :thinking), posts
 
-    posts = assert_queries(ActiveRecord::IdentityMap.enabled? ? 1 : 2) do
+    posts = assert_queries(2) do
       Post.find(:all, :include => :author, :joins => {:taggings => {:tag => :taggings}}, :conditions => "taggings_tags.super_tag_id=2", :order => 'posts.id')
     end
     assert_equal posts(:welcome, :thinking), posts
@@ -1027,7 +1027,7 @@ class EagerAssociationTest < ActiveRecord::TestCase
     assert_equal [posts(:welcome)], posts
     assert_equal authors(:david), assert_no_queries { posts[0].author}
 
-    posts = assert_queries(ActiveRecord::IdentityMap.enabled? ? 1 : 2) do
+    posts = assert_queries(2) do
       Post.find(:all, :select => 'distinct posts.*', :include => :author, :joins => ["INNER JOIN comments on comments.post_id = posts.id"], :conditions => "comments.body like 'Thank you%'", :order => 'posts.id')
     end
     assert_equal [posts(:welcome)], posts
@@ -1116,7 +1116,7 @@ class EagerAssociationTest < ActiveRecord::TestCase
   def test_preloading_empty_belongs_to_polymorphic
     t = Tagging.create!(:taggable_type => 'Post', :taggable_id => Post.maximum(:id) + 1, :tag => tags(:general))
 
-    tagging = assert_queries(ActiveRecord::IdentityMap.enabled? ? 1 : 2) { Tagging.preload(:taggable).find(t.id) }
+    tagging = assert_queries(2) { Tagging.preload(:taggable).find(t.id) }
     assert_no_queries { assert_nil tagging.taggable }
   end
 
diff --git a/activerecord/test/cases/associations/identity_map_test.rb b/activerecord/test/cases/associations/identity_map_test.rb
deleted file mode 100644
index 9b8635774c..0000000000
--- a/activerecord/test/cases/associations/identity_map_test.rb
+++ /dev/null
@@ -1,137 +0,0 @@
-require "cases/helper"
-require 'models/author'
-require 'models/post'
-
-if ActiveRecord::IdentityMap.enabled?
-class InverseHasManyIdentityMapTest < ActiveRecord::TestCase
-  fixtures :authors, :posts
-
-  def test_parent_instance_should_be_shared_with_every_child_on_find
-    m = Author.first
-    is = m.posts
-    is.each do |i|
-      assert_equal m.name, i.author.name, "Name of man should be the same before changes to parent instance"
-      m.name = 'Bongo'
-      assert_equal m.name, i.author.name, "Name of man should be the same after changes to parent instance"
-      i.author.name = 'Mungo'
-      assert_equal m.name, i.author.name, "Name of man should be the same after changes to child-owned instance"
-    end
-  end
-
-  def test_parent_instance_should_be_shared_with_eager_loaded_children
-    m = Author.find(:first, :include => :posts)
-    is = m.posts
-    is.each do |i|
-      assert_equal m.name, i.author.name, "Name of man should be the same before changes to parent instance"
-      m.name = 'Bongo'
-      assert_equal m.name, i.author.name, "Name of man should be the same after changes to parent instance"
-      i.author.name = 'Mungo'
-      assert_equal m.name, i.author.name, "Name of man should be the same after changes to child-owned instance"
-    end
-
-    m = Author.find(:first, :include => :posts, :order => 'posts.id')
-    is = m.posts
-    is.each do |i|
-      assert_equal m.name, i.author.name, "Name of man should be the same before changes to parent instance"
-      m.name = 'Bongo'
-      assert_equal m.name, i.author.name, "Name of man should be the same after changes to parent instance"
-      i.author.name = 'Mungo'
-      assert_equal m.name, i.author.name, "Name of man should be the same after changes to child-owned instance"
-    end
-  end
-
-  def test_parent_instance_should_be_shared_with_newly_built_child
-    m = Author.first
-    i = m.posts.build(:title => 'Industrial Revolution Re-enactment', :body => 'Lorem ipsum')
-    assert_not_nil i.author
-    assert_equal m.name, i.author.name, "Name of man should be the same before changes to parent instance"
-    m.name = 'Bongo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to parent instance"
-    i.author.name = 'Mungo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to just-built-child-owned instance"
-  end
-
-  def test_parent_instance_should_be_shared_with_newly_block_style_built_child
-    m = Author.first
-    i = m.posts.build {|ii| ii.title = 'Industrial Revolution Re-enactment'; ii.body = 'Lorem ipsum'}
-    assert_not_nil i.title, "Child attributes supplied to build via blocks should be populated"
-    assert_not_nil i.author
-    assert_equal m.name, i.author.name, "Name of man should be the same before changes to parent instance"
-    m.name = 'Bongo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to parent instance"
-    i.author.name = 'Mungo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to just-built-child-owned instance"
-  end
-
-  def test_parent_instance_should_be_shared_with_newly_created_child
-    m = Author.first
-    i = m.posts.create(:title => 'Industrial Revolution Re-enactment', :body => 'Lorem ipsum')
-    assert_not_nil i.author
-    assert_equal m.name, i.author.name, "Name of man should be the same before changes to parent instance"
-    m.name = 'Bongo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to parent instance"
-    i.author.name = 'Mungo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to newly-created-child-owned instance"
-  end
-
-  def test_parent_instance_should_be_shared_with_newly_created_via_bang_method_child
-    m = Author.first
-    i = m.posts.create!(:title => 'Industrial Revolution Re-enactment', :body => 'Lorem ipsum')
-    assert_not_nil i.author
-    assert_equal m.name, i.author.name, "Name of man should be the same before changes to parent instance"
-    m.name = 'Bongo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to parent instance"
-    i.author.name = 'Mungo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to newly-created-child-owned instance"
-  end
-
-  def test_parent_instance_should_be_shared_with_newly_block_style_created_child
-    m = Author.first
-    i = m.posts.create {|ii| ii.title = 'Industrial Revolution Re-enactment'; ii.body = 'Lorem ipsum'}
-    assert_not_nil i.title, "Child attributes supplied to create via blocks should be populated"
-    assert_not_nil i.author
-    assert_equal m.name, i.author.name, "Name of man should be the same before changes to parent instance"
-    m.name = 'Bongo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to parent instance"
-    i.author.name = 'Mungo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to newly-created-child-owned instance"
-  end
-
-  def test_parent_instance_should_be_shared_with_poked_in_child
-    m = Author.first
-    i = Post.create(:title => 'Industrial Revolution Re-enactment', :body => 'Lorem ipsum')
-    m.posts << i
-    assert_not_nil i.author
-    assert_equal m.name, i.author.name, "Name of man should be the same before changes to parent instance"
-    m.name = 'Bongo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to parent instance"
-    i.author.name = 'Mungo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to newly-created-child-owned instance"
-  end
-
-  def test_parent_instance_should_be_shared_with_replaced_via_accessor_children
-    m = Author.first
-    i = Post.new(:title => 'Industrial Revolution Re-enactment', :body => 'Lorem ipsum')
-    m.posts = [i]
-    assert_same m, i.author
-    assert_not_nil i.author
-    assert_equal m.name, i.author.name, "Name of man should be the same before changes to parent instance"
-    m.name = 'Bongo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to parent instance"
-    i.author.name = 'Mungo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to replaced-child-owned instance"
-  end
-
-  def test_parent_instance_should_be_shared_with_replaced_via_method_children
-    m = Author.first
-    i = Post.new(:title => 'Industrial Revolution Re-enactment', :body => 'Lorem ipsum')
-    m.posts = [i]
-    assert_not_nil i.author
-    assert_equal m.name, i.author.name, "Name of man should be the same before changes to parent instance"
-    m.name = 'Bongo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to parent instance"
-    i.author.name = 'Mungo'
-    assert_equal m.name, i.author.name, "Name of man should be the same after changes to replaced-child-owned instance"
-  end
-end
-end
diff --git a/activerecord/test/cases/autosave_association_test.rb b/activerecord/test/cases/autosave_association_test.rb
index 1376810adf..67b65c51d5 100644
--- a/activerecord/test/cases/autosave_association_test.rb
+++ b/activerecord/test/cases/autosave_association_test.rb
@@ -978,10 +978,7 @@ class TestAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCase
     values = [@pirate.reload.catchphrase, @pirate.ship.name, *@pirate.ship.parts.map(&:name)]
     # Oracle saves empty string as NULL
     if current_adapter?(:OracleAdapter)
-      expected = ActiveRecord::IdentityMap.enabled? ?
-        [nil, nil, '', ''] :
-        [nil, nil, nil, nil]
-      assert_equal expected, values
+      assert_equal [nil, nil, nil, nil], values
     else
       assert_equal ['', '', '', ''], values
     end
@@ -1077,8 +1074,7 @@ class TestAutosaveAssociationOnABelongsToAssociation < ActiveRecord::TestCase
     @ship.save(:validate => false)
     # Oracle saves empty string as NULL
     if current_adapter?(:OracleAdapter)
-      expected = ActiveRecord::IdentityMap.enabled? ?  [nil, ''] : [nil, nil]
-      assert_equal expected, [@ship.reload.name, @ship.pirate.catchphrase]
+      assert_equal [nil, nil], [@ship.reload.name, @ship.pirate.catchphrase]
     else
       assert_equal ['', ''], [@ship.reload.name, @ship.pirate.catchphrase]
     end
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index 01f647b261..76b999efac 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -1139,7 +1139,7 @@ class BasicsTest < ActiveRecord::TestCase
       assert g.save
 
       # Reload and check that we have all the geometric attributes.
-      h = ActiveRecord::IdentityMap.without { Geometric.find(g.id) }
+      h = Geometric.find(g.id)
 
       assert_equal '(5,6.1)', h.a_point
       assert_equal '[(2,3),(5.5,7)]', h.a_line_segment
@@ -1168,7 +1168,7 @@ class BasicsTest < ActiveRecord::TestCase
       assert g.save
 
       # Reload and check that we have all the geometric attributes.
-      h = ActiveRecord::IdentityMap.without { Geometric.find(g.id) }
+      h = Geometric.find(g.id)
 
       assert_equal '(5,6.1)', h.a_point
       assert_equal '[(2,3),(5.5,7)]', h.a_line_segment
diff --git a/activerecord/test/cases/helper.rb b/activerecord/test/cases/helper.rb
index 9f5f012073..5c3560a33b 100644
--- a/activerecord/test/cases/helper.rb
+++ b/activerecord/test/cases/helper.rb
@@ -19,9 +19,6 @@ require 'support/connection'
 # Show backtraces for deprecated behavior for quicker cleanup.
 ActiveSupport::Deprecation.debug = true
 
-# Enable Identity Map only when ENV['IM'] is set to "true"
-ActiveRecord::IdentityMap.enabled = (ENV['IM'] == "true")
-
 # Avoid deprecation warning setting dependent_restrict_raises to false. The default is true
 ActiveRecord::Base.dependent_restrict_raises = false
 
diff --git a/activerecord/test/cases/identity_map/middleware_test.rb b/activerecord/test/cases/identity_map/middleware_test.rb
deleted file mode 100644
index 5b32a1c6d2..0000000000
--- a/activerecord/test/cases/identity_map/middleware_test.rb
+++ /dev/null
@@ -1,74 +0,0 @@
-require "cases/helper"
-require "rack"
-
-module ActiveRecord
-  module IdentityMap
-    class MiddlewareTest < ActiveRecord::TestCase
-      def setup
-        super
-        @enabled = IdentityMap.enabled
-        IdentityMap.enabled = false
-      end
-
-      def teardown
-        super
-        IdentityMap.enabled = @enabled
-        IdentityMap.clear
-      end
-
-      def test_delegates
-        called = false
-        mw = Middleware.new lambda { |env|
-          called = true
-          [200, {}, nil]
-        }
-        mw.call({})
-        assert called, 'middleware delegated'
-      end
-
-      def test_im_enabled_during_delegation
-        mw = Middleware.new lambda { |env|
-          assert IdentityMap.enabled?, 'identity map should be enabled'
-          [200, {}, nil]
-        }
-        mw.call({})
-      end
-
-      class Enum < Struct.new(:iter)
-        def each(&b)
-          iter.call(&b)
-        end
-      end
-
-      def test_im_enabled_during_body_each
-        mw = Middleware.new lambda { |env|
-          [200, {}, Enum.new(lambda { |&b|
-            assert IdentityMap.enabled?, 'identity map should be enabled'
-            b.call "hello"
-          })]
-        }
-        body = mw.call({}).last
-        body.each { |x| assert_equal 'hello', x }
-      end
-
-      def test_im_disabled_after_body_close
-        mw = Middleware.new lambda { |env| [200, {}, []] }
-        body = mw.call({}).last
-        assert IdentityMap.enabled?, 'identity map should be enabled'
-        body.close
-        assert !IdentityMap.enabled?, 'identity map should be disabled'
-      end
-
-      def test_im_cleared_after_body_close
-        mw = Middleware.new lambda { |env| [200, {}, []] }
-        body = mw.call({}).last
-
-        IdentityMap.repository['hello'] = 'world'
-        assert !IdentityMap.repository.empty?, 'repo should not be empty'
-
-        body.close
-        assert IdentityMap.repository.empty?, 'repo should be empty'
-      end
-    end
-  end
-end
diff --git a/activerecord/test/cases/identity_map_test.rb b/activerecord/test/cases/identity_map_test.rb
deleted file mode 100644
index 3efc8bf559..0000000000
--- a/activerecord/test/cases/identity_map_test.rb
+++ /dev/null
@@ -1,439 +0,0 @@
-require "cases/helper"
-
-require 'models/developer'
-require 'models/project'
-require 'models/company'
-require 'models/topic'
-require 'models/reply'
-require 'models/computer'
-require 'models/customer'
-require 'models/order'
-require 'models/post'
-require 'models/author'
-require 'models/tag'
-require 'models/tagging'
-require 'models/comment'
-require 'models/sponsor'
-require 'models/member'
-require 'models/essay'
-require 'models/subscriber'
-require "models/pirate"
-require "models/bird"
-require "models/parrot"
-
-if ActiveRecord::IdentityMap.enabled?
-class IdentityMapTest < ActiveRecord::TestCase
-  fixtures :accounts, :companies, :developers, :projects, :topics,
-    :developers_projects, :computers, :authors, :author_addresses,
-    :posts, :tags, :taggings, :comments, :subscribers
-
-  ##############################################################################
-  # Basic tests checking if IM is functioning properly on basic find operations#
-  ##############################################################################
-
-  def test_find_id
-    assert_same(Client.find(3), Client.find(3))
-  end
-
-  def test_find_id_without_identity_map
-    ActiveRecord::IdentityMap.without do
-      assert_not_same(Client.find(3), Client.find(3))
-    end
-  end
-
-  def test_find_id_use_identity_map
-    ActiveRecord::IdentityMap.enabled = false
-    ActiveRecord::IdentityMap.use do
-      assert_same(Client.find(3), Client.find(3))
-    end
-    ActiveRecord::IdentityMap.enabled = true
-  end
-
-  def test_find_pkey
-    assert_same(
-      Subscriber.find('swistak'),
-      Subscriber.find('swistak')
-    )
-  end
-
-  def test_find_by_id
-    assert_same(
-      Client.find_by_id(3),
-      Client.find_by_id(3)
-    )
-  end
-
-  def test_find_by_string_and_numeric_id
-    assert_same(
-      Client.find_by_id("3"),
-      Client.find_by_id(3)
-    )
-  end
-
-  def test_find_by_pkey
-    assert_same(
-      Subscriber.find_by_nick('swistak'),
-      Subscriber.find_by_nick('swistak')
-    )
-  end
-
-  def test_find_first_id
-    assert_same(
-      Client.find(:first, :conditions => {:id => 1}),
-      Client.find(:first, :conditions => {:id => 1})
-    )
-  end
-
-  def test_find_first_pkey
-    assert_same(
-      Subscriber.find(:first, :conditions => {:nick => 'swistak'}),
-      Subscriber.find(:first, :conditions => {:nick => 'swistak'})
-    )
-  end
-
-  def test_queries_are_not_executed_when_finding_by_id
-    Post.find 1
-    assert_no_queries do
-      Post.find 1
-    end
-  end
-
-  ##############################################################################
-  # Tests checking if IM is functioning properly on more advanced finds        #
-  # and associations                                                           #
-  ##############################################################################
-
-  def test_owner_object_is_associated_from_identity_map
-    post = Post.find(1)
-    comment = post.comments.first
-
-    assert_no_queries do
-      comment.post
-    end
-    assert_same post, comment.post
-  end
-
-  def test_associated_object_are_assigned_from_identity_map
-    post = Post.find(1)
-
-    post.comments.each do |comment|
-      assert_same post, comment.post
-      assert_equal post.object_id, comment.post.object_id
-    end
-  end
-
-  def test_creation
-    t1 = Topic.create("title" => "t1")
-    t2 = Topic.find(t1.id)
-    assert_same(t1, t2)
-  end
-
-  ##############################################################################
-  # Tests checking if IM is functioning properly on classes with multiple      #
-  # types of inheritance                                                       #
-  ##############################################################################
-
-  def test_inherited_without_type_attribute_without_identity_map
-    ActiveRecord::IdentityMap.without do
-      p1 = DestructivePirate.create!(:catchphrase => "I'm not a regular Pirate")
-      p2 = Pirate.find(p1.id)
-      assert_not_same(p1, p2)
-    end
-  end
-
-  def test_inherited_with_type_attribute_without_identity_map
-    ActiveRecord::IdentityMap.without do
-      c = comments(:sub_special_comment)
-      c1 = SubSpecialComment.find(c.id)
-      c2 = Comment.find(c.id)
-      assert_same(c1.class, c2.class)
-    end
-  end
-
-  def test_inherited_without_type_attribute
-    p1 = DestructivePirate.create!(:catchphrase => "I'm not a regular Pirate")
-    p2 = Pirate.find(p1.id)
-    assert_not_same(p1, p2)
-  end
-
-  def test_inherited_with_type_attribute
-    c = comments(:sub_special_comment)
-    c1 = SubSpecialComment.find(c.id)
-    c2 = Comment.find(c.id)
-    assert_same(c1, c2)
-  end
-
-  ##############################################################################
-  # Tests checking dirty attribute behavior with IM                            #
-  ##############################################################################
-
-  def test_loading_new_instance_should_not_update_dirty_attributes
-    swistak = Subscriber.find(:first, :conditions => {:nick => 'swistak'})
-    swistak.name = "Swistak Sreberkowiec"
-    assert_equal(["name"], swistak.changed)
-    assert_equal({"name" => ["Marcin Raczkowski", "Swistak Sreberkowiec"]}, swistak.changes)
-
-    assert swistak.name_changed?
-    assert_equal("Swistak Sreberkowiec", swistak.name)
-  end
-
-  def test_loading_new_instance_should_change_dirty_attribute_original_value
-    swistak = Subscriber.find(:first, :conditions => {:nick => 'swistak'})
-    swistak.name = "Swistak Sreberkowiec"
-
-    Subscriber.update_all({:name => "Raczkowski Marcin"}, {:name => "Marcin Raczkowski"})
-
-    assert_equal({"name"=>["Marcin Raczkowski", "Swistak Sreberkowiec"]}, swistak.changes)
-    assert_equal("Swistak Sreberkowiec", swistak.name)
-  end
-
-  def test_loading_new_instance_should_remove_dirt
-    swistak = Subscriber.find(:first, :conditions => {:nick => 'swistak'})
-    swistak.name = "Swistak Sreberkowiec"
-
-    assert_equal({"name" => ["Marcin Raczkowski", "Swistak Sreberkowiec"]}, swistak.changes)
-
-    Subscriber.update_all({:name => "Swistak Sreberkowiec"}, {:name => "Marcin Raczkowski"})
-
-    assert_equal("Swistak Sreberkowiec", swistak.name)
-    assert_equal({"name"=>["Marcin Raczkowski", "Swistak Sreberkowiec"]}, swistak.changes)
-    assert swistak.name_changed?
-  end
-
-  def test_has_many_associations
-    pirate = Pirate.create!(:catchphrase => "Don' botharrr talkin' like one, savvy?")
-    pirate.birds.create!(:name => 'Posideons Killer')
-    pirate.birds.create!(:name => 'Killer bandita Dionne')
-
-    posideons, _ = pirate.birds
-
-    pirate.reload
-
-    pirate.birds_attributes = [{ :id => posideons.id, :name => 'Grace OMalley' }]
-    assert_equal 'Grace OMalley', pirate.birds.to_a.find { |r| r.id == posideons.id }.name
-  end
-
-  def test_changing_associations
-    post1 = Post.create("title" => "One post", "body" => "Posting...")
-    post2 = Post.create("title" => "Another post", "body" => "Posting... Again...")
-    comment = Comment.new("body" => "comment")
-
-    comment.post = post1
-    assert comment.save
-
-    assert_same(post1.comments.first, comment)
-
-    comment.post = post2
-    assert comment.save
-
-    assert_same(post2.comments.first, comment)
-    assert_equal(0, post1.comments.size)
-  end
-
-  def test_im_with_polymorphic_has_many_going_through_join_model_with_custom_select_and_joins
-    tag = posts(:welcome).tags.first
-    tag_with_joins_and_select = posts(:welcome).tags.add_joins_and_select.first
-    assert_same(tag, tag_with_joins_and_select)
-    assert_nothing_raised(NoMethodError, "Joins/select was not loaded") { tag.author_id }
-  end
-
-  ##############################################################################
-  # Tests checking Identity Map behavior with preloaded associations, joins,   #
-  # includes etc.                                                              #
-  ##############################################################################
-
-  def test_find_with_preloaded_associations
-    assert_queries(2) do
-      posts = Post.preload(:comments).order('posts.id')
-      assert posts.first.comments.first
-    end
-
-    # With IM we'll retrieve post object from previous query, it'll have comments
-    # already preloaded from first call
-    assert_queries(1) do
-      posts = Post.preload(:comments).order('posts.id')
-      assert posts.first.comments.first
-    end
-
-    assert_queries(2) do
-      posts = Post.preload(:author).order('posts.id')
-      assert posts.first.author
-    end
-
-    # With IM we'll retrieve post object from previous query, it'll have comments
-    # already preloaded from first call
-    assert_queries(1) do
-      posts = Post.preload(:author).order('posts.id')
-      assert posts.first.author
-    end
-
-    assert_queries(1) do
-      posts = Post.preload(:author, :comments).order('posts.id')
-      assert posts.first.author
-      assert posts.first.comments.first
-    end
-  end
-
-  def test_find_with_included_associations
-    assert_queries(2) do
-      posts = Post.includes(:comments).order('posts.id')
-      assert posts.first.comments.first
-    end
-
-    assert_queries(1) do
-      posts = Post.scoped.includes(:comments).order('posts.id')
-      assert posts.first.comments.first
-    end
-
-    assert_queries(2) do
-      posts = Post.includes(:author).order('posts.id')
-      assert posts.first.author
-    end
-
-    assert_queries(1) do
-      posts = Post.includes(:author, :comments).order('posts.id')
-      assert posts.first.author
-      assert posts.first.comments.first
-    end
-  end
-
-  def test_eager_loading_with_conditions_on_joined_table_preloads
-    posts = Post.find(:all, :select => 'distinct posts.*', :include => :author, :joins => [:comments], :conditions => "comments.body like 'Thank you%'", :order => 'posts.id')
-    assert_equal [posts(:welcome)], posts
-    assert_equal authors(:david), assert_no_queries { posts[0].author}
-    assert_same posts.first.author, Author.first
-
-    posts = Post.find(:all, :select => 'distinct posts.*', :include => :author, :joins => [:comments], :conditions => "comments.body like 'Thank you%'", :order => 'posts.id')
-    assert_equal [posts(:welcome)], posts
-    assert_equal authors(:david), assert_no_queries { posts[0].author}
-    assert_same posts.first.author, Author.first
-
-    posts = Post.find(:all, :include => :author, :joins => {:taggings => :tag}, :conditions => "tags.name = 'General'", :order => 'posts.id')
-    assert_equal posts(:welcome, :thinking), posts
-    assert_same posts.first.author, Author.first
-
-    posts = Post.find(:all, :include => :author, :joins => {:taggings => {:tag => :taggings}}, :conditions => "taggings_tags.super_tag_id=2", :order => 'posts.id')
-    assert_equal posts(:welcome, :thinking), posts
-    assert_same posts.first.author, Author.first
-  end
-
-  def test_eager_loading_with_conditions_on_string_joined_table_preloads
-    posts = assert_queries(2) do
-      Post.find(:all, :select => 'distinct posts.*', :include => :author, :joins => "INNER JOIN comments on comments.post_id = posts.id", :conditions => "comments.body like 'Thank you%'", :order => 'posts.id')
-    end
-    assert_equal [posts(:welcome)], posts
-    assert_equal authors(:david), assert_no_queries { posts[0].author}
-
-    posts = assert_queries(1) do
-      Post.find(:all, :select => 'distinct posts.*', :include => :author, :joins => ["INNER JOIN comments on comments.post_id = posts.id"], :conditions => "comments.body like 'Thank you%'", :order => 'posts.id')
-    end
-    assert_equal [posts(:welcome)], posts
-    assert_equal authors(:david), assert_no_queries { posts[0].author}
-  end
-
-  ##############################################################################
-  # Behaviour related to saving failures
-  ##############################################################################
-
-  def test_reload_object_if_save_failed
-    developer = Developer.first
-    developer.salary = 0
-
-    assert !developer.save
-
-    same_developer = Developer.first
-
-    assert_not_same  developer, same_developer
-    assert_not_equal 0, same_developer.salary
-    assert_not_equal developer.salary, same_developer.salary
-  end
-
-  def test_reload_object_if_forced_save_failed
-    developer = Developer.first
-    developer.salary = 0
-
-    assert_raise(ActiveRecord::RecordInvalid) { developer.save! }
-
-    same_developer = Developer.first
-
-    assert_not_same  developer, same_developer
-    assert_not_equal 0, same_developer.salary
-    assert_not_equal developer.salary, same_developer.salary
-  end
-
-  def test_reload_object_if_update_attributes_fails
-    developer = Developer.first
-    developer.salary = 0
-
-    assert !developer.update_attributes(:salary => 0)
-
-    same_developer = Developer.first
-
-    assert_not_same  developer, same_developer
-    assert_not_equal 0, same_developer.salary
-    assert_not_equal developer.salary, same_developer.salary
-  end
-
-  ##############################################################################
-  # Behaviour of readonly, frozen, destroyed
-  ##############################################################################
-
-  def test_find_using_identity_map_respects_readonly_when_loading_associated_object_first
-    author  = Author.first
-    readonly_comment = author.readonly_comments.first
-
-    comment = Comment.first
-    assert !comment.readonly?
-
-    assert readonly_comment.readonly?
-
-    assert_raise(ActiveRecord::ReadOnlyRecord) {readonly_comment.save}
-    assert comment.save
-  end
-
-  def test_find_using_identity_map_respects_readonly
-    comment = Comment.first
-    assert !comment.readonly?
-
-    author  = Author.first
-    readonly_comment = author.readonly_comments.first
-
-    assert readonly_comment.readonly?
-
-    assert_raise(ActiveRecord::ReadOnlyRecord) {readonly_comment.save}
-    assert comment.save
-  end
-
-  def test_find_using_select_and_identity_map
-    author_id, author = Author.select('id').first, Author.first
-
-    assert_equal author_id, author
-    assert_same author_id, author
-    assert_not_nil author.name
-
-    post, post_id = Post.first, Post.select('id').first
-
-    assert_equal post_id, post
-    assert_same post_id, post
-    assert_not_nil post.title
-  end
-
-# Currently AR is not allowing changing primary key (see Persistence#update)
-# So we ignore it. If this changes, this test needs to be uncommented.
-#  def test_updating_of_pkey
-#    assert client = Client.find(3),
-#    client.update_attribute(:id, 666)
-#
-#    assert Client.find(666)
-#    assert_same(client, Client.find(666))
-#
-#    s = Subscriber.find_by_nick('swistak')
-#    assert s.update_attribute(:nick, 'swistakTheJester')
-#    assert_equal('swistakTheJester', s.nick)
-#
-#    assert stj = Subscriber.find_by_nick('swistakTheJester')
-#    assert_same(s, stj)
-#  end
-
-end
-end
diff --git a/activerecord/test/cases/log_subscriber_test.rb b/activerecord/test/cases/log_subscriber_test.rb
index d1f0ace184..acd2fcdad4 100644
--- a/activerecord/test/cases/log_subscriber_test.rb
+++ b/activerecord/test/cases/log_subscriber_test.rb
@@ -11,8 +11,6 @@ class LogSubscriberTest < ActiveRecord::TestCase
 
   def setup
     @old_logger = ActiveRecord::Base.logger
-    @using_identity_map = ActiveRecord::IdentityMap.enabled?
-    ActiveRecord::IdentityMap.enabled = false
     Developer.primary_key
     super
     ActiveRecord::LogSubscriber.attach_to(:active_record)
@@ -22,7 +20,6 @@ class LogSubscriberTest < ActiveRecord::TestCase
     super
     ActiveRecord::LogSubscriber.log_subscribers.pop
     ActiveRecord::Base.logger = @old_logger
-    ActiveRecord::IdentityMap.enabled = @using_identity_map
   end
 
   def set_logger(logger)
@@ -103,13 +100,4 @@ class LogSubscriberTest < ActiveRecord::TestCase
   def test_initializes_runtime
     Thread.new { assert_equal 0, ActiveRecord::LogSubscriber.runtime }.join
   end
-
-  def test_log
-    ActiveRecord::IdentityMap.use do
-      Post.find 1
-      Post.find 1
-    end
-    wait
-    assert_match(/From Identity Map/, @logger.logged(:debug).last)
-  end
 end
diff --git a/activerecord/test/cases/query_cache_test.rb b/activerecord/test/cases/query_cache_test.rb
index f36f4237b1..d93478513b 100644
--- a/activerecord/test/cases/query_cache_test.rb
+++ b/activerecord/test/cases/query_cache_test.rb
@@ -107,7 +107,7 @@ class QueryCacheTest < ActiveRecord::TestCase
   end
 
   def test_find_queries
-    assert_queries(ActiveRecord::IdentityMap.enabled? ? 1 : 2) { Task.find(1); Task.find(1) }
+    assert_queries(2) { Task.find(1); Task.find(1) }
   end
 
   def test_find_queries_with_cache
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index acec230c72..91bc407d42 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -323,7 +323,7 @@ class RelationTest < ActiveRecord::TestCase
       assert posts.first.comments.first
     end
 
-    assert_queries(ActiveRecord::IdentityMap.enabled? ? 1 : 2) do
+    assert_queries(2) do
       posts = Post.preload(:comments).order('posts.id')
       assert posts.first.comments.first
     end
@@ -333,12 +333,12 @@ class RelationTest < ActiveRecord::TestCase
       assert posts.first.author
     end
 
-    assert_queries(ActiveRecord::IdentityMap.enabled? ? 1 : 2) do
+    assert_queries(2) do
       posts = Post.preload(:author).order('posts.id')
       assert posts.first.author
     end
 
-    assert_queries(ActiveRecord::IdentityMap.enabled? ? 1 : 3) do
+    assert_queries(3) do
       posts = Post.preload(:author, :comments).order('posts.id')
       assert posts.first.author
       assert posts.first.comments.first
@@ -351,7 +351,7 @@ class RelationTest < ActiveRecord::TestCase
       assert posts.first.comments.first
     end
 
-    assert_queries(ActiveRecord::IdentityMap.enabled? ? 1 : 2) do
+    assert_queries(2) do
       posts = Post.scoped.includes(:comments).order('posts.id')
       assert posts.first.comments.first
     end
@@ -361,7 +361,7 @@ class RelationTest < ActiveRecord::TestCase
       assert posts.first.author
     end
 
-    assert_queries(ActiveRecord::IdentityMap.enabled? ? 1 : 3) do
+    assert_queries(3) do
       posts = Post.includes(:author, :comments).order('posts.id')
       assert posts.first.author
       assert posts.first.comments.first
@@ -685,10 +685,8 @@ class RelationTest < ActiveRecord::TestCase
   end
 
   def test_relation_merging_with_preload
-    ActiveRecord::IdentityMap.without do
-      [Post.scoped.merge(Post.preload(:author)), Post.preload(:author).merge(Post.scoped)].each do |posts|
-        assert_queries(2) { assert posts.first.author }
-      end
+    [Post.scoped.merge(Post.preload(:author)), Post.preload(:author).merge(Post.scoped)].each do |posts|
+      assert_queries(2) { assert posts.first.author }
     end
   end
 
diff --git a/activerecord/test/support/connection.rb b/activerecord/test/support/connection.rb
index 11154c3797..c176316a05 100644
--- a/activerecord/test/support/connection.rb
+++ b/activerecord/test/support/connection.rb
@@ -12,7 +12,7 @@ module ARTest
   end
 
   def self.connect
-    puts "Using #{connection_name} with Identity Map #{ActiveRecord::IdentityMap.enabled? ? 'on' : 'off'}"
+    puts "Using #{connection_name}"
     ActiveRecord::Model.logger = ActiveSupport::Logger.new("debug.log")
     ActiveRecord::Model.configurations = connection_config
     ActiveRecord::Model.establish_connection 'arunit'
diff --git a/ci/travis.rb b/ci/travis.rb
index 217cda9c82..fc120f80ba 100755
--- a/ci/travis.rb
+++ b/ci/travis.rb
@@ -34,7 +34,6 @@ class Build
     self.options.update(options)
     Dir.chdir(dir) do
       announce(heading)
-      ENV['IM'] = identity_map?.inspect
       rake(*tasks)
     end
   end
@@ -45,7 +44,7 @@ class Build
 
   def heading
     heading = [gem]
-    heading << "with #{adapter} IM #{identity_map? ? 'enabled' : 'disabled'}" if activerecord?
+    heading << "with #{adapter}" if activerecord?
     heading << "in isolation" if isolated?
     heading.join(' ')
   end
@@ -61,7 +60,6 @@ class Build
   def key
     key = [gem]
     key << adapter if activerecord?
-    key << 'IM' if identity_map?
     key << 'isolated' if isolated?
     key.join(':')
   end
@@ -70,10 +68,6 @@ class Build
     gem == 'activerecord'
   end
 
-  def identity_map?
-    options[:identity_map]
-  end
-
   def isolated?
     options[:isolated]
   end
@@ -107,7 +101,6 @@ ENV['GEM'].split(',').each do |gem|
     results[build.key] = build.run!
 
     if build.activerecord?
-      build.options[:identity_map] = true
       results[build.key] = build.run!
     end
   end
diff --git a/railties/guides/source/configuring.textile b/railties/guides/source/configuring.textile
index 49b15bd650..79980be5ef 100644
--- a/railties/guides/source/configuring.textile
+++ b/railties/guides/source/configuring.textile
@@ -288,8 +288,6 @@ h4. Configuring Active Record
 
 * +config.active_record.whitelist_attributes+ will create an empty whitelist of attributes available for mass-assignment security for all models in your app.
 
-* +config.active_record.identity_map+ controls whether the identity map is enabled, and is false by default.
-
 * +config.active_record.auto_explain_threshold_in_seconds+ configures the threshold for automatic EXPLAINs (+nil+ disables this feature). Queries exceeding the threshold get their query plan logged. Default is 0.5 in development mode.
 
 * +config.active_record.dependent_restrict_raises+ will control the behavior when an object with a <tt>:dependent => :restrict</tt> association is deleted. Setting this to false will prevent +DeleteRestrictionError+ from being raised and instead will add an error on the model object. Defaults to false in the development mode.
diff --git a/railties/guides/source/upgrading_ruby_on_rails.textile b/railties/guides/source/upgrading_ruby_on_rails.textile
index 731d56c850..e63548abc9 100644
--- a/railties/guides/source/upgrading_ruby_on_rails.textile
+++ b/railties/guides/source/upgrading_ruby_on_rails.textile
@@ -34,6 +34,10 @@ h4(#plugins4_0). vendor/plugins
 
 Rails 4.0 no longer supports loading plugins from <tt>vendor/plugins</tt>. You must replace any plugins by extracting them to gems and adding them to your Gemfile. If you choose not to make them gems, you can move them into, say, <tt>lib/my_plugin/*</tt> and add an appropriate initializer in <tt>config/initializers/my_plugin.rb</tt>.
 
+h4(#identity_map4_0). IdentityMap
+
+Rails 4.0 has removed <tt>IdentityMap</tt> from <tt>ActiveRecord</tt>, due to "some inconsistencies with associations":https://github.com/rails/rails/commit/302c912bf6bcd0fa200d964ec2dc4a44abe328a6. If you have manually enabled it in your application, you will have to remove the following config that has no effect anymore: <tt>config.active_record.identity_map</tt>.
+
 h3. Upgrading from Rails 3.1 to Rails 3.2
 
 If your application is currently on any version of Rails older than 3.1.x, you should upgrade to Rails 3.1 before attempting an update to Rails 3.2.
diff --git a/railties/lib/rails/test_help.rb b/railties/lib/rails/test_help.rb
index 11e4353c87..46bf3bbe48 100644
--- a/railties/lib/rails/test_help.rb
+++ b/railties/lib/rails/test_help.rb
@@ -18,10 +18,6 @@ if defined?(ActiveRecord::Base)
   class ActiveSupport::TestCase
     include ActiveRecord::TestFixtures
     self.fixture_path = "#{Rails.root}/test/fixtures/"
-
-    setup do
-      ActiveRecord::IdentityMap.clear
-    end
   end
 
   ActionDispatch::IntegrationTest.fixture_path = ActiveSupport::TestCase.fixture_path
diff --git a/railties/test/application/middleware_test.rb b/railties/test/application/middleware_test.rb
index 712a555c4a..e6f85918f6 100644
--- a/railties/test/application/middleware_test.rb
+++ b/railties/test/application/middleware_test.rb
@@ -115,7 +115,6 @@ module ApplicationTests
       boot!
       assert !middleware.include?("ActiveRecord::ConnectionAdapters::ConnectionManagement")
       assert !middleware.include?("ActiveRecord::QueryCache")
-      assert !middleware.include?("ActiveRecord::IdentityMap::Middleware")
     end
 
     test "removes lock if allow concurrency is set" do
@@ -173,12 +172,6 @@ module ApplicationTests
       assert_equal "Rack::Runtime", middleware.fourth
     end
 
-    test "identity map is inserted" do
-      add_to_config "config.active_record.identity_map = true"
-      boot!
-      assert middleware.include?("ActiveRecord::IdentityMap::Middleware")
-    end
-
     test "insert middleware before" do
       add_to_config "config.middleware.insert_before ActionDispatch::Static, Rack::Config"
       boot!