Rails 4.0.0 (unreleased)

Explain only normal CRUD sql (select / update / insert / delete). Fix problem that explains unexplainable sql. Closes #7544 #6458.

kennyj

Fix find_in_batches when primary_key is set other than id. You can now use this method with the primary key which is not integer-based.

Example:

class Post < ActiveRecord::Base
  self.primary_key = :title
end

Post.find_in_batches(start: 'My First Post') do |batch|
  batch.each { |post| post.author.greeting }
end

Toshiyuki Kawanishi

You can now override the generated accessor methods for stored attributes and reuse the original behavior with read_store_attribute and write_store_attribute, which are counterparts to read_attribute and write_attribute.

Matt Jones

Accept belongs_to (including polymorphic) association keys in queries.

The following queries are now equivalent:

Post.where(author: author)
Post.where(author_id: author)

PriceEstimate.where(estimate_of: treasure)
PriceEstimate.where(estimate_of_type: 'Treasure', estimate_of_id: treasure)

Peter Brown

Use native mysqldump command instead of structure_dump method when dumping the database structure to a sql file. Fixes #5547.

kennyj
PostgreSQL inet and cidr types are converted to IPAddr objects.

Dan McClain
PostgreSQL array type support. Any datatype can be used to create an array column, with full migration and schema dumper support.

To declare an array column, use the following syntax:
```
create_table :table_with_arrays do |t|
  t.integer :int_array, array: true
  # integer[]
  t.integer :int_array, array: true, :length => 2
  # smallint[]
  t.string :string_array, array: true, length: 30
  # char varying(30)[]
end
```
This respects any other migration detail (limits, defaults, etc). ActiveRecord will serialize and deserialize the array columns on their way to and from the database.

One thing to note: PostgreSQL does not enforce any limits on the number of elements, and any array can be multi-dimensional. Any array that is multi-dimensional must be rectangular (each sub array must have the same number of elements as its siblings).

If the pg_array_parser gem is available, it will be used when parsing PostgreSQL's array representation.

Dan McClain
Attribute predicate methods, such as article.title?, will now raise ActiveModel::MissingAttributeError if the attribute being queried for truthiness was not read from the database, instead of just returning false.

Ernie Miller
ActiveRecord::SchemaDumper uses Ruby 1.9 style hash, which means that the schema.rb file will be generated using this new syntax from now on.

Konstantin Shabanov
Map interval with precision to string datatype in PostgreSQL. Fixes #7518.

Yves Senn
Fix eagerly loading associations without primary keys. Fixes #4976.

Kelley Reynolds
Rails now raise an exception when you're trying to run a migration that has an invalid file name. Only lower case letters, numbers, and '_' are allowed in migration's file name. Please see #7419 for more details.

Jan Bernacki
Fix bug when calling store_accessor multiple times. Fixes #7532.

Matt Jones
Fix store attributes that show the changes incorrectly. Fixes #7532.

Matt Jones
Fix ActiveRecord::Relation#pluck when columns or tables are reserved words.

Ian Lesperance
Allow JSON columns to be created in PostgreSQL and properly encoded/decoded. to/from database.

Dickson S. Guedes
Fix time column type casting for invalid time string values to correctly return nil.

Adam Meehan
Allow to pass Symbol or Proc into :limit option of #accepts_nested_attributes_for.

Mikhail Dieterle
ActiveRecord::SessionStore has been extracted from Active Record as activerecord-session_store gem. Please read the README.md file on the gem for the usage.

Prem Sichanugrist
Fix reset_counters when there are multiple belongs_to association with the same foreign key and one of them have a counter cache. Fixes #5200.

Dave Desrochers
serialized_attributes and _attr_readonly become class method only. Instance reader methods are deprecated.

kennyj
Round usec when comparing timestamp attributes in the dirty tracking. Fixes #6975.

kennyj
Use inversed parent for first and last child of has_many association.

Ravil Bayramgalin
Fix Column.microseconds and Column.fast_string_to_date to avoid converting timestamp seconds to a float, since it occasionally results in inaccuracies with microsecond-precision times. Fixes #7352.

Ari Pollak
Raise ArgumentError if list of attributes to change is empty in update_all.

Roman Shatsov
Fix AR#create to return an unsaved record when AR::RecordInvalid is raised. Fixes #3217.

Dave Yeu
Fixed table name prefix that is generated in engines for namespaced models.

Wojciech Wnętrzak
Make sure :environment task is executed before db:schema:load or db:structure:load. Fixes #4772.

Seamus Abshere

Allow Relation#merge to take a proc.

This was requested by DHH to allow creating of one's own custom association macros.

For example:

module Commentable
  def has_many_comments(extra)
    has_many :comments, -> { where(:foo).merge(extra) }
  end
end

class Post < ActiveRecord::Base
  extend Commentable
  has_many_comments -> { where(:bar) }
end

Jon Leighton

Add CollectionProxy#scope.

This can be used to get a Relation from an association.

Previously we had a #scoped method, but we're deprecating that for AR::Base, so it doesn't make sense to have it here.

This was requested by DHH, to facilitate code like this:

Project.scope.order('created_at DESC').page(current_page).tagged_with(@tag).limit(5).scoping do
  @topics      = @project.topics.scope
  @todolists   = @project.todolists.scope
  @attachments = @project.attachments.scope
  @documents   = @project.documents.scope
end

Jon Leighton

Add Relation#load.

This method explicitly loads the records and then returns self.

Rather than deciding between "do I want an array or a relation?", most people are actually asking themselves "do I want to eager load or lazy load?" Therefore, this method provides a way to explicitly eager-load without having to switch from a Relation to an array.

Example:
```
@posts = Post.where(published: true).load
```
Jon Leighton
Model.all now returns an ActiveRecord::Relation, rather than an array of records. Use Relation#to_a if you really want an array.

In some specific cases, this may cause breakage when upgrading. However in most cases the ActiveRecord::Relation will just act as a lazy-loaded array and there will be no problems.

Note that calling Model.all with options (e.g. Model.all(conditions: '...') was already deprecated, but it will still return an array in order to make the transition easier.

Model.scoped is deprecated in favour of Model.all.

Relation#all still returns an array, but is deprecated (since it would serve no purpose if we made it return a Relation).

Jon Leighton
:finder_sql and :counter_sql options on collection associations are deprecated. Please transition to using scopes.

Jon Leighton
:insert_sql and :delete_sql options on has_and_belongs_to_many associations are deprecated. Please transition to using has_many :through.

Jon Leighton
The migration generator now creates a join table with (commented) indexes every time the migration name contains the word join_table:
```
rails g migration create_join_table_for_artists_and_musics artist_id:index music_id
```
Aleksey Magusev

Add add_reference and remove_reference schema statements. Aliases, add_belongs_to and remove_belongs_to are acceptable. References are reversible.

Examples:

# Create a user_id column
add_reference(:products, :user)
# Create a supplier_id, supplier_type columns and appropriate index
add_reference(:products, :supplier, polymorphic: true, index: true)
# Remove polymorphic reference
remove_reference(:products, :supplier, polymorphic: true)

Aleksey Magusev

Add :default and :null options to column_exists?.

column_exists?(:testings, :taggable_id, :integer, null: false)
column_exists?(:testings, :taggable_type, :string, default: 'Photo')

Aleksey Magusev

ActiveRecord::Relation#inspect now makes it clear that you are dealing with a Relation object rather than an array:.
```
User.where(age: 30).inspect
# => <ActiveRecord::Relation [#<User ...>, #<User ...>, ...]>

User.where(age: 30).to_a.inspect
# => [#<User ...>, #<User ...>]
```
The number of records displayed will be limited to 10.

Brian Cardarella, Jon Leighton & Damien Mathieu

Add collation and ctype support to PostgreSQL. These are available for PostgreSQL 8.4 or later. Example:

development:
  adapter: postgresql
  host: localhost
  database: rails_development
  username: foo
  password: bar
  encoding: UTF8
  collation: ja_JP.UTF8
  ctype: ja_JP.UTF8

kennyj

Changed validates_presence_of on an association so that children objects do not validate as being present if they are marked for destruction. This prevents you from saving the parent successfully and thus putting the parent in an invalid state.

Nick Monje & Brent Wheeldon
FinderMethods#exists? now returns false with the false argument.

Egor Lynko
Added support for specifying the precision of a timestamp in the postgresql adapter. So, instead of having to incorrectly specify the precision using the :limit option, you may use :precision, as intended. For example, in a migration:
```
def change
  create_table :foobars do |t|
    t.timestamps :precision => 0
  end
end
```
Tony Schneider
Allow ActiveRecord::Relation#pluck to accept multiple columns. Returns an array of arrays containing the typecasted values:
```
Person.pluck(:id, :name)
# SELECT people.id, people.name FROM people
# [[1, 'David'], [2, 'Jeremy'], [3, 'Jose']]
```
Jeroen van Ingen & Carlos Antonio da Silva

Improve the derivation of HABTM join table name to take account of nesting. It now takes the table names of the two models, sorts them lexically and then joins them, stripping any common prefix from the second table name.

Some examples:

Top level models (Category <=> Product)
Old: categories_products
New: categories_products

Top level models with a global table_name_prefix (Category <=> Product)
Old: site_categories_products
New: site_categories_products

Nested models in a module without a table_name_prefix method (Admin::Category <=> Admin::Product)
Old: categories_products
New: categories_products

Nested models in a module with a table_name_prefix method (Admin::Category <=> Admin::Product)
Old: categories_products
New: admin_categories_products

Nested models in a parent model (Catalog::Category <=> Catalog::Product)
Old: categories_products
New: catalog_categories_products

Nested models in different parent models (Catalog::Category <=> Content::Page)
Old: categories_pages
New: catalog_categories_content_pages

Andrew White

Move HABTM validity checks to ActiveRecord::Reflection. One side effect of this is to move when the exceptions are raised from the point of declaration to when the association is built. This is consistant with other association validity checks.

Andrew White
Added stored_attributes hash which contains the attributes stored using ActiveRecord::Store. This allows you to retrieve the list of attributes you've defined.

class User < ActiveRecord::Base store :settings, accessors: [:color, :homepage] end

User.stored_attributes[:settings] # [:color, :homepage]

Joost Baaij & Carlos Antonio da Silva
PostgreSQL default log level is now 'warning', to bypass the noisy notice messages. You can change the log level using the min_messages option available in your config/database.yml.

kennyj
Add uuid datatype support to PostgreSQL adapter.

Konstantin Shabanov
Added ActiveRecord::Migration.check_pending! that raises an error if migrations are pending.

Richard Schneeman
Added #destroy! which acts like #destroy but will raise an ActiveRecord::RecordNotDestroyed exception instead of returning false.

Marc-André Lafortune
Allow blocks for count with ActiveRecord::Relation, to work similar as Array#count:
```
Person.where("age > 26").count { |person| person.gender == 'female' }
```
Chris Finne & Carlos Antonio da Silva
Added support to CollectionAssociation#delete for passing fixnum or string values as record ids. This finds the records responding to the id and executes delete on them.
```
class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.delete("1") # => [#<Pet id: 1>]
person.pets.delete(2, 3) # => [#<Pet id: 2>, #<Pet id: 3>]
```
Francesco Rodriguez
Deprecated most of the 'dynamic finder' methods. All dynamic methods except for find_by_... and find_by_...! are deprecated. Here's how you can rewrite the code:
- find_all_by_... can be rewritten using where(...)
- find_last_by_... can be rewritten using where(...).last
- scoped_by_... can be rewritten using where(...)
- find_or_initialize_by_... can be rewritten using where(...).first_or_initialize
- find_or_create_by_... can be rewritten using where(...).first_or_create
- find_or_create_by_...! can be rewritten using where(...).first_or_create!
The implementation of the deprecated dynamic finders has been moved to the activerecord-deprecated_finders gem. See below for details.

Jon Leighton
Deprecated the old-style hash based finder API. This means that methods which previously accepted "finder options" no longer do. For example this:
```
Post.find(:all, conditions: { comments_count: 10 }, limit: 5)
```
Should be rewritten in the new style which has existed since Rails 3:
```
Post.where(comments_count: 10).limit(5)
```
Note that as an interim step, it is possible to rewrite the above as:
```
Post.all.merge(where: { comments_count: 10 }, limit: 5)
```
This could save you a lot of work if there is a lot of old-style finder usage in your application.

Relation#merge now accepts a hash of options, but they must be identical to the names of the equivalent finder method. These are mostly identical to the old-style finder option names, except in the following cases:
- :conditions becomes :where.
- :include becomes :includes.
- :extend becomes :extending.
The code to implement the deprecated features has been moved out to the activerecord-deprecated_finders gem. This gem is a dependency of Active Record in Rails 4.0. It will no longer be a dependency from Rails 4.1, but if your app relies on the deprecated features then you can add it to your own Gemfile. It will be maintained by the Rails core team until Rails 5.0 is released.

Jon Leighton
It's not possible anymore to destroy a model marked as read only.

Johannes Barre
Added ability to ActiveRecord::Relation#from to accept other ActiveRecord::Relation objects.

Record.from(subquery) Record.from(subquery, :a)

Radoslav Stankov
Added custom coders support for ActiveRecord::Store. Now you can set your custom coder like this:
```
store :settings, accessors: [ :color, :homepage ], coder: JSON
```
Andrey Voronkov
mysql and mysql2 connections will set SQL_MODE=STRICT_ALL_TABLES by default to avoid silent data loss. This can be disabled by specifying strict: false in your database.yml.

Michael Pearson
Added default order to first to assure consistent results among diferent database engines. Introduced take as a replacement to the old behavior of first.

Marcelo Silveira
Added an :index option to automatically create indexes for references and belongs_to statements in migrations.

The references and belongs_to methods now support an index option that receives either a boolean value or an options hash that is identical to options available to the add_index method:

create_table :messages do |t| t.references :person, index: true end

Is the same as:

create_table :messages do |t| t.references :person end add_index :messages, :person_id

Generators have also been updated to use the new syntax.

Joshua Wood
Added bang methods for mutating ActiveRecord::Relation objects. For example, while foo.where(:bar) will return a new object leaving foo unchanged, foo.where!(:bar) will mutate the foo object

Jon Leighton
Added #find_by and #find_by! to mirror the functionality provided by dynamic finders in a way that allows dynamic input more easily:
```
Post.find_by name: 'Spartacus', rating: 4
Post.find_by "published_at < ?", 2.weeks.ago
Post.find_by! name: 'Spartacus'
```
Jon Leighton
Added ActiveRecord::Base#slice to return a hash of the given methods with their names as keys and returned values as values.

Guillermo Iguaran

Deprecate eager-evaluated scopes.

Don't use this:

scope :red, where(color: 'red')
default_scope where(color: 'red')

Use this:

scope :red, -> { where(color: 'red') }
default_scope { where(color: 'red') }

The former has numerous issues. It is a common newbie gotcha to do the following:

scope :recent, where(published_at: Time.now - 2.weeks)

Or a more subtle variant:

scope :recent, -> { where(published_at: Time.now - 2.weeks) }
scope :recent_red, recent.where(color: 'red')

Eager scopes are also very complex to implement within Active Record, and there are still bugs. For example, the following does not do what you expect:

scope :remove_conditions, except(:where)
where(...).remove_conditions # => still has conditions

Jon Leighton

Remove IdentityMap

IdentityMap has never graduated to be an "enabled-by-default" feature, due to some inconsistencies with associations, as described in this commit:

https://github.com/rails/rails/commit/302c912bf6bcd0fa200d964ec2dc4a44abe328a6

Hence the removal from the codebase, until such issues are fixed.

Carlos Antonio da Silva
Added the schema cache dump feature.

Schema cache dump feature was implemetend. This feature can dump/load internal state of SchemaCache instance because we want to boot rails more quickly when we have many models.

Usage notes:
1. execute rake task. RAILS_ENV=production bundle exec rake db:schema:cache:dump => generate db/schema_cache.dump
2. add config.active_record.use_schema_cache_dump = true in config/production.rb. BTW, true is default.
3. boot rails. RAILS_ENV=production bundle exec rails server => use db/schema_cache.dump
4. If you remove clear dumped cache, execute rake task. RAILS_ENV=production bundle exec rake db:schema:cache:clear => remove db/schema_cache.dump
kennyj
Added support for partial indices to PostgreSQL adapter.

The add_index method now supports a where option that receives a string with the partial index criteria.
```
add_index(:accounts, :code, where: 'active')

Generates

CREATE INDEX index_accounts_on_code ON accounts(code) WHERE active
```
Marcelo Silveira
Implemented ActiveRecord::Relation#none method.

The none method returns a chainable relation with zero records (an instance of the NullRelation class).

Any subsequent condition chained to the returned relation will continue generating an empty relation and will not fire any query to the database.

Juanjo Bazán
Added the ActiveRecord::NullRelation class implementing the null object pattern for the Relation class.

Juanjo Bazán
Added new dependent: :restrict_with_error option. This will add an error to the model, rather than raising an exception.

The :restrict option is renamed to :restrict_with_exception to make this distinction explicit.

Manoj Kumar & Jon Leighton

Added create_join_table migration helper to create HABTM join tables.

create_join_table :products, :categories
# =>
# create_table :categories_products, id: false do |td|
#   td.integer :product_id,  null: false
#   td.integer :category_id, null: false
# end

Rafael Mendonça França

The primary key is always initialized in the @attributes hash to nil (unless another value has been specified).

Aaron Paterson
In previous releases, the following would generate a single query with an OUTER JOIN comments, rather than two separate queries:
```
Post.includes(:comments)
    .where("comments.name = 'foo'")
```
This behaviour relies on matching SQL string, which is an inherently flawed idea unless we write an SQL parser, which we do not wish to do.

Therefore, it is now deprecated.

To avoid deprecation warnings and for future compatibility, you must explicitly state which tables you reference, when using SQL snippets:
```
Post.includes(:comments)
    .where("comments.name = 'foo'")
    .references(:comments)
```
Note that you do not need to explicitly specify references in the following cases, as they can be automatically inferred:
```
Post.where(comments: { name: 'foo' })
Post.where('comments.name' => 'foo')
Post.order('comments.name')
```
You also do not need to worry about this unless you are doing eager loading. Basically, don't worry unless you see a deprecation warning or (in future releases) an SQL error due to a missing JOIN.

Jon Leighton
Support for the schema_info table has been dropped. Please switch to schema_migrations.

Aaron Patterson
Connections must be closed at the end of a thread. If not, your connection pool can fill and an exception will be raised.

Aaron Patterson
Added the ActiveRecord::Model module which can be included in a class as an alternative to inheriting from ActiveRecord::Base:
```
class Post
  include ActiveRecord::Model
end
```
Please note:
- Up until now it has been safe to assume that all AR models are descendants of ActiveRecord::Base. This is no longer a safe assumption, but it may transpire that there are areas of the code which still make this assumption. So there may be 'teething difficulties' with this feature. (But please do try it and report bugs.)
- Plugins & libraries etc that add methods to ActiveRecord::Base will not be compatible with ActiveRecord::Model. Those libraries should add to ActiveRecord::Model instead (which is included in Base), or better still, avoid monkey-patching AR and instead provide a module that users can include where they need it.
- To minimise the risk of conflicts with other code, it is advisable to include ActiveRecord::Model early in your class definition.
Jon Leighton
PostgreSQL hstore records can be created.

Aaron Patterson
PostgreSQL hstore types are automatically deserialized from the database.

Aaron Patterson

Please check 3-2-stable for previous changes.

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CHANGELOG.md

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Rails 4.0.0 (unreleased)

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Rails 4.0.0 (unreleased)