Mongoid now has its own identity map. This project has been deprecated.
Mongoid Identity Map is a simple and transparent Identity Map implementation for the Mongoid ODM.
In Gemfile:
gem "mongoid_identity_map"
Identity map is applied automatically to all queries that return a single model.
A rack middleware - MongoidIdentityMap::ClearMiddleware - is provided for clearing the identity map after each request. In a Rails app, this middleware is automatically added to the list of middlewares.
You can also clear the identity map by calling MongoidIdentityMap::IdentityMap.clear.
Currently, it's an all or nothing deal. It is not possible to turn the identiy map on or off on a class (Mongoid::Document) basis.
Identity map is applied only on queries that return a single model. Queries that return a cursor are not affected.