This ticket has now been changed to deprecate the use of the criteria cache. The Mongoid::QueryCache is more effective in caching queries and all caching functionality should be delegated there.

Original ticket:
===========

Mongo context has this usage of try_cache for example:

      def count(options = {}, &block)
        return super(&block) if block_given?
        try_cache(:count) { view.count_documents(options) }
      end

This seems to imply that the options to count aren't part of the cache key. However count can be limited, suggesting that if I call count with limit 1 and then count with no limit I may receive wrong result (count=1 instead of actual count).

To reproduce this, criteria must be explicitly cached:

irb(main):026:0> c = Band.all
=> 
#<Mongoid::Criteria
...
irb(main):027:0> cc = c.cache
=> 
#<Mongoid::Criteria
...
irb(main):028:0> cc.count(limit: 4)
=> 4
irb(main):029:0> cc.count(limit: 5)
=> 4

To fix this, try_cache calls must pass in options applicable to the query in each invocation, for example limit in the case of count above.