class ActiveRecord::Relation

Active Record Relation

Constants

CLAUSE_METHODS
INVALID_METHODS_FOR_DELETE_ALL
MULTI_VALUE_METHODS
SINGLE_VALUE_METHODS
VALUE_METHODS

Attributes

klass[R]
loaded[R]
loaded?[R]
model[R]
predicate_builder[R]
table[R]

Public Class Methods

new(klass, table, predicate_builder, values = {}) click to toggle source
# File lib/active_record/relation.rb, line 22
def initialize(klass, table, predicate_builder, values = {})
  @klass  = klass
  @table  = table
  @values = values
  @offsets = {}
  @loaded = false
  @predicate_builder = predicate_builder
end

Public Instance Methods

==(other) click to toggle source

Compares two relations for equality.

# File lib/active_record/relation.rb, line 612
def ==(other)
  case other
  when Associations::CollectionProxy, AssociationRelation
    self == other.records
  when Relation
    other.to_sql == to_sql
  when Array
    records == other
  end
end
any?() click to toggle source

Returns true if there are any records.

Calls superclass method
# File lib/active_record/relation.rb, line 282
def any?
  return super if block_given?
  !empty?
end
blank?() click to toggle source

Returns true if relation is blank.

# File lib/active_record/relation.rb, line 628
def blank?
  records.blank?
end
build(*args, &block)
Alias for: new
cache_key(timestamp_column = :updated_at) click to toggle source

Returns a cache key that can be used to identify the records fetched by this query. The cache key is built with a fingerprint of the sql query, the number of records matched by the query and a timestamp of the last updated record. When a new record comes to match the query, or any of the existing records is updated or deleted, the cache key changes.

Product.where("name like ?", "%Cosmic Encounter%").cache_key
# => "products/query-1850ab3d302391b85b8693e941286659-1-20150714212553907087000"

If the collection is loaded, the method will iterate through the records to generate the timestamp, otherwise it will trigger one SQL query like:

SELECT COUNT(*), MAX("products"."updated_at") FROM "products" WHERE (name like '%Cosmic Encounter%')

You can also pass a custom timestamp column to fetch the timestamp of the last updated record.

Product.where("name like ?", "%Game%").cache_key(:last_reviewed_at)

You can customize the strategy to generate the key on a per model basis overriding ActiveRecord::Base#collection_cache_key.

# File lib/active_record/relation.rb, line 320
def cache_key(timestamp_column = :updated_at)
  @cache_keys ||= {}
  @cache_keys[timestamp_column] ||= @klass.collection_cache_key(self, timestamp_column)
end
create(*args, &block) click to toggle source

Tries to create a new record with the same scoped attributes defined in the relation. Returns the initialized object if validation fails.

Expects arguments in the same format as ActiveRecord::Base.create.

Examples

users = User.where(name: 'Oscar')
users.create # => #<User id: 3, name: "Oscar", ...>

users.create(name: 'fxn')
users.create # => #<User id: 4, name: "fxn", ...>

users.create { |user| user.name = 'tenderlove' }
# => #<User id: 5, name: "tenderlove", ...>

users.create(name: nil) # validation on name
# => #<User id: nil, name: nil, ...>
# File lib/active_record/relation.rb, line 145
def create(*args, &block)
  scoping { @klass.create(*args, &block) }
end
create!(*args, &block) click to toggle source

Similar to create, but calls create! on the base class. Raises an exception if a validation error occurs.

Expects arguments in the same format as ActiveRecord::Base.create!.

# File lib/active_record/relation.rb, line 155
def create!(*args, &block)
  scoping { @klass.create!(*args, &block) }
end
delete(id_or_array) click to toggle source

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.

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])
# File lib/active_record/relation.rb, line 535
def delete(id_or_array)
  where(primary_key => id_or_array).delete_all
end
delete_all() click to toggle source

Deletes the records 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.

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.

If an invalid method is supplied, delete_all raises an ActiveRecordError:

Post.limit(100).delete_all
# => ActiveRecord::ActiveRecordError: delete_all doesn't support limit
# File lib/active_record/relation.rb, line 492
def delete_all
  invalid_methods = INVALID_METHODS_FOR_DELETE_ALL.select do |method|
    value = get_value(method)
    SINGLE_VALUE_METHODS.include?(method) ? value : value.any?
  end
  if invalid_methods.any?
    raise ActiveRecordError.new("delete_all doesn't support #{invalid_methods.join(', ')}")
  end

  stmt = Arel::DeleteManager.new
  stmt.from(table)

  if has_join_values?
    @klass.connection.join_to_delete(stmt, arel, arel_attribute(primary_key))
  else
    stmt.wheres = arel.constraints
  end

  affected = @klass.connection.delete(stmt, "SQL", bound_attributes)

  reset
  affected
end
destroy(id) click to toggle source

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 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)
# File lib/active_record/relation.rb, line 466
def destroy(id)
  if id.is_a?(Array)
    id.map { |one_id| destroy(one_id) }
  else
    find(id).destroy
  end
end
destroy_all() click to toggle source

Destroys the records by instantiating each record and calling its #destroy method. Each object's callbacks are executed (including :dependent association options). 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.

Examples

Person.where(age: 0..18).destroy_all
# File lib/active_record/relation.rb, line 443
def destroy_all
  records.each(&:destroy).tap { reset }
end
eager_loading?() click to toggle source

Returns true if relation needs eager loading.

# File lib/active_record/relation.rb, line 597
def eager_loading?
  @should_eager_load ||=
    eager_load_values.any? ||
    includes_values.any? && (joined_includes_values.any? || references_eager_loaded_tables?)
end
empty?() click to toggle source

Returns true if there are no records.

# File lib/active_record/relation.rb, line 270
def empty?
  return @records.empty? if loaded?
  !exists?
end
encode_with(coder) click to toggle source

Serializes the relation objects Array.

# File lib/active_record/relation.rb, line 260
def encode_with(coder)
  coder.represent_seq(nil, records)
end
explain() click to toggle source

Runs EXPLAIN on the query or queries triggered by this relation and returns the result as a string. The string is formatted imitating the ones printed by the database shell.

Note that this method actually runs the queries, since the results of some are needed by the next ones when eager loading is going on.

Please see further details in the Active Record Query Interface guide.

# File lib/active_record/relation.rb, line 245
def explain
  exec_explain(collecting_queries_for_explain { exec_queries })
end
find_or_create_by(attributes, &block) click to toggle source

Finds the first record with the given attributes, or creates a record with the attributes if one is not found:

# Find the first user named "Penélope" or create a new one.
User.find_or_create_by(first_name: 'Penélope')
# => #<User id: 1, first_name: "Penélope", last_name: nil>

# Find the first user named "Penélope" or create a new one.
# We already have one so the existing record will be returned.
User.find_or_create_by(first_name: 'Penélope')
# => #<User id: 1, first_name: "Penélope", last_name: nil>

# Find the first user named "Scarlett" or create a new one with
# a particular last name.
User.create_with(last_name: 'Johansson').find_or_create_by(first_name: 'Scarlett')
# => #<User id: 2, first_name: "Scarlett", last_name: "Johansson">

This method accepts a block, which is passed down to create. The last example above can be alternatively written this way:

# Find the first user named "Scarlett" or create a new one with a
# different last name.
User.find_or_create_by(first_name: 'Scarlett') do |user|
  user.last_name = 'Johansson'
end
# => #<User id: 2, first_name: "Scarlett", last_name: "Johansson">

This method always returns a record, but if creation was attempted and failed due to validation errors it won't be persisted, you get what create returns in such situation.

Please note *this method is not atomic*, it runs first a SELECT, and if there are no results an INSERT is attempted. If there are other threads or processes there is a race condition between both calls and it could be the case that you end up with two similar records.

Whether that is a problem or not depends on the logic of the application, but in the particular case in which rows have a UNIQUE constraint an exception may be raised, just retry:

begin
  CreditAccount.transaction(requires_new: true) do
    CreditAccount.find_or_create_by(user_id: user.id)
  end
rescue ActiveRecord::RecordNotUnique
  retry
end
# File lib/active_record/relation.rb, line 219
def find_or_create_by(attributes, &block)
  find_by(attributes) || create(attributes, &block)
end
find_or_create_by!(attributes, &block) click to toggle source

Like find_or_create_by, but calls create! so an exception is raised if the created record is invalid.

# File lib/active_record/relation.rb, line 226
def find_or_create_by!(attributes, &block)
  find_by(attributes) || create!(attributes, &block)
end
find_or_initialize_by(attributes, &block) click to toggle source

Like find_or_create_by, but calls new instead of create.

# File lib/active_record/relation.rb, line 232
def find_or_initialize_by(attributes, &block)
  find_by(attributes) || new(attributes, &block)
end
initialize_copy(other) click to toggle source
# File lib/active_record/relation.rb, line 31
def initialize_copy(other)
  @values = @values.dup
  reset
end
inspect() click to toggle source
# File lib/active_record/relation.rb, line 636
def inspect
  subject = loaded? ? records : self
  entries = subject.take([limit_value, 11].compact.min).map!(&:inspect)

  entries[10] = "..." if entries.size == 11

  "#<#{self.class.name} [#{entries.join(', ')}]>"
end
joined_includes_values() click to toggle source

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] }

# File lib/active_record/relation.rb, line 607
def joined_includes_values
  includes_values & joins_values
end
load(&block) click to toggle source

Causes the records to be loaded from the database if they have not been loaded already. You can use this if for some reason you need to explicitly load some records before actually using them. The return value is the relation itself, not the records.

Post.where(published: true).load # => #<ActiveRecord::Relation>
# File lib/active_record/relation.rb, line 545
def load(&block)
  exec_queries(&block) unless loaded?

  self
end
many?() click to toggle source

Returns true if there is more than one record.

Calls superclass method
# File lib/active_record/relation.rb, line 294
def many?
  return super if block_given?
  limit_value ? records.many? : size > 1
end
new(*args, &block) click to toggle source

Initializes new record from relation while maintaining the current scope.

Expects arguments in the same format as ActiveRecord::Base.new.

users = User.where(name: 'DHH')
user = users.new # => #<User id: nil, name: "DHH", created_at: nil, updated_at: nil>

You can also pass a block to new with the new record as argument:

user = users.new { |user| user.name = 'Oscar' }
user.name # => Oscar
# File lib/active_record/relation.rb, line 120
def new(*args, &block)
  scoping { @klass.new(*args, &block) }
end
Also aliased as: build
none?() click to toggle source

Returns true if there are no records.

Calls superclass method
# File lib/active_record/relation.rb, line 276
def none?
  return super if block_given?
  empty?
end
one?() click to toggle source

Returns true if there is exactly one record.

Calls superclass method
# File lib/active_record/relation.rb, line 288
def one?
  return super if block_given?
  limit_value ? records.one? : size == 1
end
pretty_print(q) click to toggle source
# File lib/active_record/relation.rb, line 623
def pretty_print(q)
  q.pp(records)
end
reload() click to toggle source

Forces reloading of relation.

# File lib/active_record/relation.rb, line 552
def reload
  reset
  load
end
reset() click to toggle source
# File lib/active_record/relation.rb, line 557
def reset
  @last = @to_sql = @order_clause = @scope_for_create = @arel = @loaded = nil
  @should_eager_load = @join_dependency = nil
  @records = [].freeze
  @offsets = {}
  self
end
scope_for_create() click to toggle source
# File lib/active_record/relation.rb, line 592
def scope_for_create
  @scope_for_create ||= where_values_hash.merge(create_with_value)
end
scoping() { || ... } click to toggle source

Scope all queries to the current scope.

Comment.where(post_id: 1).scoping do
  Comment.first
end
# => SELECT "comments".* FROM "comments" WHERE "comments"."post_id" = 1 ORDER BY "comments"."id" ASC LIMIT 1

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

# File lib/active_record/relation.rb, line 334
def scoping
  previous, klass.current_scope = klass.current_scope(true), self
  yield
ensure
  klass.current_scope = previous
end
size() click to toggle source

Returns size of the records.

# File lib/active_record/relation.rb, line 265
def size
  loaded? ? @records.length : count(:all)
end
to_a() click to toggle source

Converts relation objects to Array.

# File lib/active_record/relation.rb, line 250
def to_a
  records.dup
end
to_sql() click to toggle source

Returns sql statement for the relation.

User.where(name: 'Oscar').to_sql
# => SELECT "users".* FROM "users"  WHERE "users"."name" = 'Oscar'
# File lib/active_record/relation.rb, line 569
def to_sql
  @to_sql ||= begin
                relation = self

                if eager_loading?
                  find_with_associations { |rel| relation = rel }
                end

                conn = klass.connection
                conn.unprepared_statement {
                  conn.to_sql(relation.arel, relation.bound_attributes)
                }
              end
end
update(id = :all, attributes) click to toggle source

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 multiple records from the result of a relation
people = Person.where(group: 'expert')
people.update(group: 'masters')

Note: Updating a large number of records will run an UPDATE query for each record, which may cause a performance issue. So if it is not needed to run callbacks for each update, it is preferred to use update_all for updating all records using a single query.

# File lib/active_record/relation.rb, line 409
    def update(id = :all, attributes)
      if id.is_a?(Array)
        id.map.with_index { |one_id, idx| update(one_id, attributes[idx]) }
      elsif id == :all
        records.each { |record| record.update(attributes) }
      else
        if ActiveRecord::Base === id
          raise ArgumentError, "            You are passing an instance of ActiveRecord::Base to `update`.
            Please pass the id of the object by calling `.id`.
".squish
        end
        object = find(id)
        object.update(attributes)
        object
      end
    end
update_all(updates) click to toggle source

Updates all records in the current relation with details given. 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. However, values passed to update_all will still go through Active Record's normal type casting and serialization.

Parameters

  • updates - A string, array, or hash representing the SET part of an SQL statement.

Examples

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

# Update all books with 'Rails' in their title
Book.where('title LIKE ?', '%Rails%').update_all(author: 'David')

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

# Update all invoices and set the number column to its id value.
Invoice.update_all('number = id')
# File lib/active_record/relation.rb, line 363
def update_all(updates)
  raise ArgumentError, "Empty list of attributes to change" if updates.blank?

  stmt = Arel::UpdateManager.new

  stmt.set Arel.sql(@klass.send(:sanitize_sql_for_assignment, updates))
  stmt.table(table)

  if has_join_values?
    @klass.connection.join_to_update(stmt, arel, arel_attribute(primary_key))
  else
    stmt.key = arel_attribute(primary_key)
    stmt.take(arel.limit)
    stmt.order(*arel.orders)
    stmt.wheres = arel.constraints
  end

  @klass.connection.update stmt, "SQL", bound_attributes
end
values() click to toggle source
# File lib/active_record/relation.rb, line 632
def values
  @values.dup
end
where_values_hash(relation_table_name = table_name) click to toggle source

Returns a hash of where conditions.

User.where(name: 'Oscar').where_values_hash
# => {name: "Oscar"}
# File lib/active_record/relation.rb, line 588
def where_values_hash(relation_table_name = table_name)
  where_clause.to_h(relation_table_name)
end

Protected Instance Methods

load_records(records) click to toggle source
# File lib/active_record/relation.rb, line 655
def load_records(records)
  @records = records.freeze
  @loaded = true
end

Private Instance Methods

build_preloader() click to toggle source
# File lib/active_record/relation.rb, line 683
def build_preloader
  ActiveRecord::Associations::Preloader.new
end
exec_queries(&block) click to toggle source
# File lib/active_record/relation.rb, line 666
def exec_queries(&block)
  @records = eager_loading? ? find_with_associations.freeze : @klass.find_by_sql(arel, bound_attributes, &block).freeze

  preload = preload_values
  preload += includes_values unless eager_loading?
  preloader = nil
  preload.each do |associations|
    preloader ||= build_preloader
    preloader.preload @records, associations
  end

  @records.each(&:readonly!) if readonly_value

  @loaded = true
  @records
end
has_join_values?() click to toggle source
# File lib/active_record/relation.rb, line 662
def has_join_values?
  joins_values.any? || left_outer_joins_values.any?
end
references_eager_loaded_tables?() click to toggle source
# File lib/active_record/relation.rb, line 687
def references_eager_loaded_tables?
  joined_tables = arel.join_sources.map do |join|
    if join.is_a?(Arel::Nodes::StringJoin)
      tables_in_string(join.left)
    else
      [join.left.table_name, join.left.table_alias]
    end
  end

  joined_tables += [table.name, table.table_alias]

  # always convert table names to downcase as in Oracle quoted table names are in uppercase
  joined_tables = joined_tables.flatten.compact.map(&:downcase).uniq

  (references_values - joined_tables).any?
end
tables_in_string(string) click to toggle source
# File lib/active_record/relation.rb, line 704
def tables_in_string(string)
  return [] if string.blank?
  # always convert table names to downcase as in Oracle quoted table names are in uppercase
  # ignore raw_sql_ that is used by Oracle adapter as alias for limit/offset subqueries
  string.scan(/([a-zA-Z_][.\w]+).?\./).flatten.map(&:downcase).uniq - ["raw_sql_"]
end