class ActiveRecord::Relation

Active Record Relation

Constants

JoinOperation
MULTI_VALUE_METHODS
SINGLE_VALUE_METHODS
VALUE_METHODS

Attributes

default_scoped[RW]
default_scoped?[RW]
klass[R]
loaded[R]
loaded?[R]
model[R]
proxy_association[RW]
table[R]

Public Class Methods

new(klass, table, values = {}) click to toggle source
# File lib/active_record/relation.rb, line 24
def initialize(klass, table, values = {})
  @klass             = klass
  @table             = table
  @values            = values
  @implicit_readonly = nil
  @loaded            = false
  @default_scoped    = false
end

Public Instance Methods

==(other) click to toggle source

Compares two relations for equality.

# File lib/active_record/relation.rb, line 539
def ==(other)
  case other
  when Relation
    other.to_sql == to_sql
  when Array
    to_a == other
  end
end
any?() { |*block_args| ... } click to toggle source

Returns true if there are any records.

# File lib/active_record/relation.rb, line 241
def any?
  if block_given?
    to_a.any? { |*block_args| yield(*block_args) }
  else
    !empty?
  end
end
blank?() click to toggle source

Returns true if relation is blank.

# File lib/active_record/relation.rb, line 563
def blank?
  to_a.blank?
end
build(*args, &block)
Alias for: new
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 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 119
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 Base.create!.

# File lib/active_record/relation.rb, line 127
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 459
def delete(id_or_array)
  where(primary_key => id_or_array).delete_all
end
delete_all(conditions = nil) click to toggle source

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.

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.

If a limit scope is supplied, delete_all raises an ActiveRecord error:

Post.limit(100).delete_all
# => ActiveRecord::ActiveRecordError: delete_all doesn't support limit scope
# File lib/active_record/relation.rb, line 418
def delete_all(conditions = nil)
  raise ActiveRecordError.new("delete_all doesn't support limit scope") if self.limit_value

  if conditions
    where(conditions).delete_all
  else
    stmt = Arel::DeleteManager.new(arel.engine)
    stmt.from(table)

    if with_default_scope.joins_values.any?
      @klass.connection.join_to_delete(stmt, arel, table[primary_key])
    else
      stmt.wheres = arel.constraints
    end

    affected = @klass.connection.delete(stmt, 'SQL', bind_values)

    reset
    affected
  end
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 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)
# File lib/active_record/relation.rb, line 391
def destroy(id)
  if id.is_a?(Array)
    id.map { |one_id| destroy(one_id) }
  else
    find(id).destroy
  end
end
destroy_all(conditions = nil) click to toggle source

Destroys the records matching conditions 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.

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
# File lib/active_record/relation.rb, line 364
def destroy_all(conditions = nil)
  if conditions
    where(conditions).destroy_all
  else
    to_a.each {|object| object.destroy }.tap { reset }
  end
end
eager_loading?() click to toggle source

Returns true if relation needs eager loading.

# File lib/active_record/relation.rb, line 518
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 233
def empty?
  return @records.empty? if loaded?

  c = count
  c.respond_to?(:zero?) ? c.zero? : c.empty?
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 213
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.find_or_create_by(user_id: user.id)
rescue ActiveRecord::RecordNotUnique
  retry
end
# File lib/active_record/relation.rb, line 189
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 195
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 200
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 33
def initialize_copy(other)
  # This method is a hot spot, so for now, use Hash[] to dup the hash.
  #   https://bugs.ruby-lang.org/issues/7166
  @values        = Hash[@values]
  @values[:bind] = @values[:bind].dup if @values.key? :bind
  reset
end
insert(values) click to toggle source
# File lib/active_record/relation.rb, line 41
def insert(values)
  primary_key_value = nil

  if primary_key && Hash === values
    primary_key_value = values[values.keys.find { |k|
      k.name == primary_key
    }]

    if !primary_key_value && connection.prefetch_primary_key?(klass.table_name)
      primary_key_value = connection.next_sequence_value(klass.sequence_name)
      values[klass.arel_table[klass.primary_key]] = primary_key_value
    end
  end

  im = arel.create_insert
  im.into @table

  conn = @klass.connection

  substitutes = values.sort_by { |arel_attr,_| arel_attr.name }
  binds       = substitutes.map do |arel_attr, value|
    [@klass.columns_hash[arel_attr.name], value]
  end

  substitutes.each_with_index do |tuple, i|
    tuple[1] = conn.substitute_at(binds[i][0], i)
  end

  if values.empty? # empty insert
    im.values = Arel.sql(connection.empty_insert_statement_value)
  else
    im.insert substitutes
  end

  conn.insert(
    im,
    'SQL',
    primary_key,
    primary_key_value,
    nil,
    binds)
end
inspect() click to toggle source
# File lib/active_record/relation.rb, line 571
def inspect
  entries = to_a.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 528
def joined_includes_values
  includes_values & joins_values
end
load() 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 469
def load
  exec_queries unless loaded?

  self
end
many?() { |*block_args| ... } click to toggle source

Returns true if there is more than one record.

# File lib/active_record/relation.rb, line 250
def many?
  if block_given?
    to_a.many? { |*block_args| yield(*block_args) }
  else
    limit_value ? to_a.many? : size > 1
  end
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 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 96
def new(*args, &block)
  scoping { @klass.new(*args, &block) }
end
Also aliased as: build
pretty_print(q) click to toggle source
# File lib/active_record/relation.rb, line 548
def pretty_print(q)
  q.pp(self.to_a)
end
reload() click to toggle source

Forces reloading of relation.

# File lib/active_record/relation.rb, line 476
def reload
  reset
  load
end
reset() click to toggle source
# File lib/active_record/relation.rb, line 481
def reset
  @first = @last = @to_sql = @order_clause = @scope_for_create = @arel = @loaded = nil
  @should_eager_load = @join_dependency = nil
  @records = []
  self
end
scope_for_create() click to toggle source
# File lib/active_record/relation.rb, line 513
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 267
def scoping
  previous, klass.current_scope = klass.current_scope, 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 228
def size
  loaded? ? @records.length : count
end
to_a() click to toggle source

Converts relation objects to Array.

# File lib/active_record/relation.rb, line 218
def to_a
  load
  @records
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 492
def to_sql
  @to_sql ||= klass.connection.to_sql(arel, bind_values.dup)
end
uniq_value() click to toggle source

uniq and uniq! are silently deprecated. uniq_value delegates to distinct_value to maintain backwards compatibility. Use distinct_value instead.

# File lib/active_record/relation.rb, line 534
def uniq_value
  distinct_value
end
update(id, 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)
# File lib/active_record/relation.rb, line 329
def update(id, attributes)
  if id.is_a?(Array)
    id.map.with_index { |one_id, idx| update(one_id, attributes[idx]) }
  else
    object = find(id)
    object.update(attributes)
    object
  end
end
update_all(updates) click to toggle source

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.

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')
# File lib/active_record/relation.rb, line 293
def update_all(updates)
  raise ArgumentError, "Empty list of attributes to change" if updates.blank?

  stmt = Arel::UpdateManager.new(arel.engine)

  stmt.set Arel.sql(@klass.send(:sanitize_sql_for_assignment, updates))
  stmt.table(table)
  stmt.key = table[primary_key]

  if with_default_scope.joins_values.any?
    @klass.connection.join_to_update(stmt, arel)
  else
    stmt.take(arel.limit)
    stmt.order(*arel.orders)
    stmt.wheres = arel.constraints
  end

  @klass.connection.update stmt, 'SQL', bind_values
end
values() click to toggle source
# File lib/active_record/relation.rb, line 567
def values
  Hash[@values]
end
where_values_hash() 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 500
def where_values_hash
  equalities = with_default_scope.where_values.grep(Arel::Nodes::Equality).find_all { |node|
    node.left.relation.name == table_name
  }

  binds = Hash[bind_values.find_all(&:first).map { |column, v| [column.name, v] }]

  Hash[equalities.map { |where|
    name = where.left.name
    [name, binds.fetch(name.to_s) { where.right }]
  }]
end

Private Instance Methods

exec_queries() click to toggle source
# File lib/active_record/relation.rb, line 580
def exec_queries
  default_scoped = with_default_scope

  if default_scoped.equal?(self)
    @records = eager_loading? ? find_with_associations : @klass.find_by_sql(arel, bind_values)

    preload = preload_values
    preload +=  includes_values unless eager_loading?
    preload.each do |associations|
      ActiveRecord::Associations::Preloader.new(@records, associations).run
    end

    # @readonly_value is true only if set explicitly. @implicit_readonly is true if there
    # are JOINS and no explicit SELECT.
    readonly = readonly_value.nil? ? @implicit_readonly : readonly_value
    @records.each { |record| record.readonly! } if readonly
  else
    @records = default_scoped.to_a
  end

  @loaded = true
  @records
end
references_eager_loaded_tables?() click to toggle source
# File lib/active_record/relation.rb, line 604
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 { |t| t.downcase }.uniq
  string_tables = tables_in_string(to_sql)

  if (references_values - joined_tables).any?
    true
  elsif !ActiveRecord::Base.disable_implicit_join_references &&
        (string_tables - joined_tables).any?
    ActiveSupport::Deprecation.warn(
      "It looks like you are eager loading table(s) (one of: #{string_tables.join(', ')}) "            "that are referenced in a string SQL snippet. For example: \n"            "\n"            "    Post.includes(:comments).where(\"comments.title = 'foo'\")\n"            "\n"            "Currently, Active Record recognizes the table in the string, and knows to JOIN the "            "comments table to the query, rather than loading comments in a separate query. "            "However, doing this without writing a full-blown SQL parser is inherently flawed. "            "Since we don't want to write an SQL parser, we are removing this functionality. "            "From now on, you must explicitly tell Active Record when you are referencing a table "            "from a string:\n"            "\n"            "    Post.includes(:comments).where(\"comments.title = 'foo'\").references(:comments)\n"            "\n"            "If you don't rely on implicit join references you can disable the feature entirely "            "by setting `config.active_record.disable_implicit_join_references = true`."
    )
    true
  else
    false
  end
end
tables_in_string(string) click to toggle source
# File lib/active_record/relation.rb, line 647
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{ |s| s.downcase }.uniq - ['raw_sql_']
end