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Expand changelog and upgrading rails guide with IdentityMap info

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1 parent a8dd21d commit dde3058c3a7350d6e28d602a1f57fe908075bbe7 @carlosantoniodasilva carlosantoniodasilva committed Mar 4, 2012
Showing with 14 additions and 1 deletion.
  1. +10 −1 activerecord/
  2. +4 −0 railties/guides/source/upgrading_ruby_on_rails.textile
11 activerecord/
@@ -1,6 +1,15 @@
## Rails 4.0.0 (unreleased) ##
-* Remove IdentityMap *Carlos Antonio da Silva*
+* Remove IdentityMap
+ IdentityMap has never graduated to be an "enabled-by-default" feature, due
+ to some inconsistencies with associations, as described in this commit:
+ Hence the removal from the codebase, until such issues are fixed.
+ *Carlos Antonio da Silva*
* Added the schema cache dump feature.
4 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": 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.

1 comment on commit dde3058

gamov commented on dde3058 Mar 20, 2012

That's so sad... IdentityMap would be such a performance boost if working properly.
In 2012, it's so stupid that loading a model from two different side of an association doesn't return the same object.

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