Added test to ensure that DescendantsTracker does not leak memory on singleton classes
Change ActionController::Parameters#require behavior when value is empty
When the value for the required key is empty an ActionController::ParameterMissing is raised which gets caught by ActionController::Base and turned into a 400 Bad Request reply with a message in the body saying the key is missing, which is misleading.

With these changes, ActionController::EmptyParameter will be raised which ActionController::Base will catch and turn into a 400 Bad Request reply with a message in the body saying the key value is empty.
Fixed a bug in  when using has_many association with :inverse_of option and UUID primary key.
Remove unnecessary require from active_support/inflector/methods.rb

`active_support/inflections` already requires
`active_support/inflector/inflections`. There's no need to require it in
`active_support/inflector/methods`.
Fix that #pluck wasn't rescuing ThrowResult, meaning it would blow up when failing to construct_limited_ids_condition.
Add coverage for the fact that pluck without an argument returns all the table's columns.
No point in memoizing a simple literal string.
Make NullRelation a bit more like a real relation by returning 0 for #calculate(:count)
Rather than raising ThrowResult when construct_limited_ids_conditions comes up empty, set the relation to NullRelation and rely on its results.

This will help avoid errors like 2fcafee250ee2, because in most cases NullRelation will do the right thing. Minor bonus is avoiding the use of exceptions for flow control.
change to destructive `deep_symbolize_keys` after https://github.com/rails/rails/commit/df24b8790f22384a068fece7042f04ffd2fcb33e which allows to do so. This helps to avoid extra hash object creation, by symbolizing inplace
Use `Base.strict_decode64` instead of `Base.decode64` just as we do in encoding;

Also reduce extra object allocation by creating string directly instead of join on Array
make "rails dbconsole" work with activerecord-postgis-adapter
Update filter_parameters related docs, as they have been moved to initializers.
Update configuration docs for assets.enabled, as it's set true by default in the configuration and doesn't appear in the config files anymore.
update_counters accepts a hash, not an array of hashes
Documentation: Notifications queue does not run in a thread.
In rails 4 there are much more ways to retrieve a single object
Compare with the parsed result from REXML backend
Added an example for primary_key option
Add test for AR::CounterCache.update_counters