Active Record Query Interface 3.0Published about 2 years agoI’ve been working on revamping the Active Record query interface for the last few weeks ( while taking some time off in India from consulting work, before joining 37signals ), building on top of Emilio’s GSOC project of integrating ARel and ActiveRecord. So here’s an overview of how things are going to work in Rails 3.

What’s going to be deprecated in Rails 3.1 ?

These deprecations will be effective in Rails’ 3.1 release ( NOT Rails 3 ) and will be fully removed in Rails 3.2, though there will be an official plugin to continue supporting them. Consider this an advance warning as it involves changing a lot of code.

In short, passing options hash containing :conditions, :include, :joins, :limit, :offset, :order, :select, :readonly, :group, :having, :from, :lock to any of the ActiveRecord provided class methods, is now deprecated.

Going into details, currently ActiveRecord provides the following finder methods :

  • find(id_or_array_of_ids, options)
  • find(:first, options)
  • find(:all, options)
  • first(options)
  • all(options)
  • update_all(updates, conditions, options)

    • And the following calculation methods :

  • count(column, options)
  • average(column, options)
  • minimum(column, options)
  • maximum(column, options)
  • sum(column, options)
  • calculate(operation, column, options)

    • Starting with Rails 3, supplying any option to the methods above will be deprecated. Support for supplying options will be removed from Rails 3.2. Moreover, find(:first) and find(:all) ( without any options ) are also being deprecated in favour of first and all. A tiny little exception here is that count() will still accept a :distinct option.

    The following shows a few example of the deprecated usages :

    But the following is NOT deprecated :

    Additionally, supplying options hash to named_scope is also deprecated :

    Supplying options hash to with_scope, with_exclusive_scope and default_scope has also been deprecated :

    Dynamic scoped_by_ are also going to be deprecated :

    New API

    ActiveRecord in Rails 3 will have the following new finder methods.

  • where (:conditions)
  • having (:conditions)
  • select
  • group
  • order
  • limit
  • offset
  • joins
  • includes (:include)
  • lock
  • readonly
  • from

    • Chainability

    All of the above methods returns a Relation. Conceptually, a relation is very similar to an anonymous named scope. All these methods are defined on the Relation object as well, making it possible to chain them.

    You could also apply more finders to the existing relations :

    Quacks like a Model

    A relation quacks just like a model when it comes to the primary CRUD methods. You could call any of the following methods on a relation :

  • new(attributes)
  • create(attributes)
  • create!(attributes)
  • find(id_or_array)
  • destroy(id_or_array)
  • destroy_all
  • delete(id_or_array)
  • delete_all
  • update(ids, updates)
  • update_all(updates)
    • ... Lire la suite de l'article