# 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 `id`s.

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