rails/activerecord/CHANGELOG.md

• Do not load all child records for inverse case.

  currently post.comments.find(Comment.first.id) would load all comments for the given post to set the inverse association.

  This has a huge performance penalty. Because if post has 100k records and all these 100k records would be loaded in memory even though the comment id was supplied.

  Fix is to use in-memory records only if loaded? is true. Otherwise load the records using full sql.

  Fixes #10509.

  Neeraj Singh

• Fixture setup does no longer depend on ActiveRecord::Base.configurations. This is relevant when ENV["DATABASE_URL"] is used in place of a database.yml.

  Yves Senn

• Fix mysql2 adapter raises the correct exception when executing a query on a closed connection.

  Yves Senn

• Ambiguous reflections are on :through relationships are no longer supported. For example, you need to change this:

  class Author < ActiveRecord::Base
    has_many :posts
    has_many :taggings, :through => :posts
  end
  
  class Post < ActiveRecord::Base
    has_one :tagging
    has_many :taggings
  end
  
  class Tagging < ActiveRecord::Base
  end
  

  To this:

  class Author < ActiveRecord::Base
    has_many :posts
    has_many :taggings, :through => :posts, :source => :tagging
  end
  
  class Post < ActiveRecord::Base
    has_one :tagging
    has_many :taggings
  end
  
  class Tagging < ActiveRecord::Base
  end
  

  Aaron Peterson

• Remove column restrictions for count, let the database raise if the SQL is invalid. The previous behavior was untested and surprising for the user. Fixes #5554.

  Example:

  User.select("name, username").count
  # Before => SELECT count(*) FROM users
  # After => ActiveRecord::StatementInvalid
  
  # you can still use `count(:all)` to perform a query unrelated to the
  # selected columns
  User.select("name, username").count(:all) # => SELECT count(*) FROM users
  

  Yves Senn

• Rails now automatically detects inverse associations. If you do not set the :inverse_of option on the association, then Active Record will guess the inverse association based on heuristics.

  Note that automatic inverse detection only works on has_many, has_one, and belongs_to associations. Extra options on the associations will also prevent the association's inverse from being found automatically.

  The automatic guessing of the inverse association uses a heuristic based on the name of the class, so it may not work for all associations, especially the ones with non-standard names.

  You can turn off the automatic detection of inverse associations by setting the :inverse_of option to false like so:

  class Taggable < ActiveRecord::Base
    belongs_to :tag, inverse_of: false
  end
  

  John Wang

• Fix add_column with array option when using PostgreSQL. Fixes #10432

  Adam Anderson

• Usage of implicit_readonly is being removed. Please use readonlymethod explicitly to mark records asreadonly. Fixes #10615.

  Example:

  user = User.joins(:todos).select("users.*, todos.title as todos_title").readonly(true).first
  user.todos_title = 'clean pet'
  user.save! # will raise error
  

  Yves Senn

• Fix the :primary_key option for has_many associations. Fixes #10693.

  Yves Senn

• Fix bug where tiny types are incorrectly coerced as boolean when the length is more than 1.

  Fixes #10620.

  Aaron Peterson

• Also support extensions in PostgreSQL 9.1. This feature has been supported since 9.1.

  kennyj

• Deprecate ConnectionAdapters::SchemaStatements#distinct, as it is no longer used by internals.

  Ben Woosley

• Fix pending migrations error when loading schema and ActiveRecord::Base.table_name_prefix is not blank.

  Call assume_migrated_upto_version on connection to prevent it from first being picked up in method_missing.

  In the base class, Migration, method_missing expects the argument to be a table name, and calls proper_table_name on the arguments before sending to connection. If table_name_prefix or table_name_suffix is used, the schema version changes to prefix_version_suffix, breaking rake test:prepare.

  Fixes #10411.

  Kyle Stevens

• Method read_attribute_before_type_cast should accept input as symbol.

  Neeraj Singh

• Confirm a record has not already been destroyed before decrementing counter cache.

  Ben Tucker

• Fixed a bug in ActiveRecord#sanitize_sql_hash_for_conditions in which self.class is an argument to PredicateBuilder#build_from_hash causing PredicateBuilder to call non-existent method Class#reflect_on_association.

  Zach Ohlgren

• While removing index if column option is missing then raise IrreversibleMigration exception.

  Following code should raise IrreversibleMigration. But the code was failing since options is an array and not a hash.

  def change
    change_table :users do |t|
      t.remove_index [:name, :email]
    end
  end
  

  Fix was to check if the options is a Hash before operating on it.

  Fixes #10419.

  Neeraj Singh

• Do not overwrite manually built records during one-to-one nested attribute assignment

  For one-to-one nested associations, if you build the new (in-memory) child object yourself before assignment, then the NestedAttributes module will not overwrite it, e.g.:

  class Member < ActiveRecord::Base
    has_one :avatar
    accepts_nested_attributes_for :avatar
  
    def avatar
      super || build_avatar(width: 200)
    end
  end
  
  member = Member.new
  member.avatar_attributes = {icon: 'sad'}
  member.avatar.width # => 200
  

  Olek Janiszewski

• fixes bug introduced by #3329. Now, when autosaving associations, deletions happen before inserts and saves. This prevents a 'duplicate unique value' database error that would occur if a record being created had the same value on a unique indexed field as that of a record being destroyed.

  Johnny Holton

• Handle aliased attributes in ActiveRecord::Relation.

  When using symbol keys, ActiveRecord will now translate aliased attribute names to the actual column name used in the database:

  With the model

  class Topic
    alias_attribute :heading, :title
  end
  

  The call

  Topic.where(heading: 'The First Topic')
  

  should yield the same result as

  Topic.where(title: 'The First Topic')
  

  This also applies to ActiveRecord::Relation::Calculations calls such as Model.sum(:aliased) and Model.pluck(:aliased).

  This will not work with SQL fragment strings like Model.sum('DISTINCT aliased').

  Godfrey Chan

• Mute psql output when running rake db:schema:load.

  Godfrey Chan

• Trigger a save on has_one association=(associate) when the associate contents have changed.

  Fix #8856.

  Chris Thompson

• Abort a rake task when missing db/structure.sql like db:schema:load task.

  kennyj

• rake:db:test:prepare falls back to original environment after execution.

  Slava Markevich

Please check 4-0-stable for previous changes.