Class ActiveRecord::Relation
In: lib/active_record/relation.rb
Parent: Object

Active Record Relation

Methods

Included Modules

FinderMethods Calculations SpawnMethods QueryMethods Batches

Constants

JoinOperation = Struct.new(:relation, :join_class, :on)
ASSOCIATION_METHODS = [:includes, :eager_load, :preload]
MULTI_VALUE_METHODS = [:select, :group, :order, :joins, :where, :having, :bind]
SINGLE_VALUE_METHODS = [:limit, :offset, :lock, :readonly, :from, :reorder, :reverse_order]

External Aliases

loaded -> loaded?
default_scoped -> default_scoped?

Attributes

default_scoped  [RW] 
extensions  [RW] 
klass  [R] 
loaded  [R] 
table  [R] 

Public Class methods

Public Instance methods

build(*args, &block)

Alias for new

Deletes the row with a primary key matching the id argument, using a SQL DELETE statement, and returns the number of rows deleted. Active Record objects are not instantiated, so the object‘s callbacks are not executed, including any :dependent association options or Observer methods.

You can delete multiple rows at once by passing an Array of ids.

Note: Although it is often much faster than the alternative, destroy, skipping callbacks might bypass business logic in your application that ensures referential integrity or performs other essential jobs.

Examples

  # Delete a single row
  Todo.delete(1)

  # Delete multiple rows
  Todo.delete([2,3,4])

Deletes the records matching conditions without instantiating the records first, and hence not calling the destroy method nor invoking callbacks. This is a single SQL DELETE statement that goes straight to the database, much more efficient than destroy_all. Be careful with relations though, in particular :dependent rules defined on associations are not honored. Returns the number of rows affected.

Parameters

  • conditions - Conditions are specified the same way as with find method.

Example

  Post.delete_all("person_id = 5 AND (category = 'Something' OR category = 'Else')")
  Post.delete_all(["person_id = ? AND (category = ? OR category = ?)", 5, 'Something', 'Else'])
  Post.where(:person_id => 5).where(:category => ['Something', 'Else']).delete_all

Both calls delete the affected posts all at once with a single DELETE statement. If you need to destroy dependent associations or call your before_* or after_destroy callbacks, use the destroy_all method instead.

Destroy an object (or multiple objects) that has the given id, the object is instantiated first, therefore all callbacks and filters are fired off before the object is deleted. This method is less efficient than ActiveRecord#delete but allows cleanup methods and other actions to be run.

This essentially finds the object (or multiple objects) with the given id, creates a new object from the attributes, and then calls destroy on it.

Parameters

  • id - Can be either an Integer or an Array of Integers.

Examples

  # Destroy a single object
  Todo.destroy(1)

  # Destroy multiple objects
  todos = [1,2,3]
  Todo.destroy(todos)

Destroys the records matching conditions by instantiating each record and calling its destroy method. Each object‘s callbacks are executed (including :dependent association options and before_destroy/after_destroy Observer methods). Returns the collection of objects that were destroyed; each will be frozen, to reflect that no changes should be made (since they can‘t be persisted).

Note: Instantiation, callback execution, and deletion of each record can be time consuming when you‘re removing many records at once. It generates at least one SQL DELETE query per record (or possibly more, to enforce your callbacks). If you want to delete many rows quickly, without concern for their associations or callbacks, use delete_all instead.

Parameters

  • conditions - A string, array, or hash that specifies which records to destroy. If omitted, all records are destroyed. See the Conditions section in the introduction to ActiveRecord::Base for more information.

Examples

  Person.destroy_all("last_login < '2004-04-04'")
  Person.destroy_all(:status => "inactive")
  Person.where(:age => 0..18).destroy_all

Returns true if there are no records.

Joins that are also marked for preloading. In which case we should just eager load them. Note that this is a naive implementation because we could have strings and symbols which represent the same association, but that aren‘t matched by this. Also, we could have nested hashes which partially match, e.g. { :a => :b } & { :a => [:b, :c] }

Scope all queries to the current scope.

Example

  Comment.where(:post_id => 1).scoping do
    Comment.first # SELECT * FROM comments WHERE post_id = 1
  end

Please check unscoped if you want to remove all previous scopes (including the default_scope) during the execution of a block.

Returns size of the records.

Updates an object (or multiple objects) and saves it to the database, if validations pass. The resulting object is returned whether the object was saved successfully to the database or not.

Parameters

  • id - This should be the id or an array of ids to be updated.
  • attributes - This should be a hash of attributes or an array of hashes.

Examples

  # Updates one record
  Person.update(15, :user_name => 'Samuel', :group => 'expert')

  # Updates multiple records
  people = { 1 => { "first_name" => "David" }, 2 => { "first_name" => "Jeremy" } }
  Person.update(people.keys, people.values)

Updates all records with details given if they match a set of conditions supplied, limits and order can also be supplied. This method constructs a single SQL UPDATE statement and sends it straight to the database. It does not instantiate the involved models and it does not trigger Active Record callbacks or validations.

Parameters

  • updates - A string, array, or hash representing the SET part of an SQL statement.
  • conditions - A string, array, or hash representing the WHERE part of an SQL statement. See conditions in the intro.
  • options - Additional options are :limit and :order, see the examples for usage.

Examples

  # Update all customers with the given attributes
  Customer.update_all :wants_email => true

  # Update all books with 'Rails' in their title
  Book.update_all "author = 'David'", "title LIKE '%Rails%'"

  # Update all avatars migrated more than a week ago
  Avatar.update_all ['migrated_at = ?', Time.now.utc], ['migrated_at > ?', 1.week.ago]

  # Update all books that match conditions, but limit it to 5 ordered by date
  Book.update_all "author = 'David'", "title LIKE '%Rails%'", :order => 'created_at', :limit => 5

  # Conditions from the current relation also works
  Book.where('title LIKE ?', '%Rails%').update_all(:author => 'David')

  # The same idea applies to limit and order
  Book.where('title LIKE ?', '%Rails%').order(:created_at).limit(5).update_all(:author => 'David')

Protected Instance methods

[Validate]