Module: ActiveRecord::QueryMethods

Includes:
ActiveModel::ForbiddenAttributesProtection
Included in:
Relation
Defined in:
lib/active_record/relation/query_methods.rb

Defined Under Namespace

Classes: CTEJoin, WhereChain

Constant Summary collapse

FROZEN_EMPTY_ARRAY = 
[].freeze
FROZEN_EMPTY_HASH = 
{}.freeze
VALID_UNSCOPING_VALUES = 
Set.new([:where, :select, :group, :order, :lock,
:limit, :offset, :joins, :left_outer_joins, :annotate,
:includes, :eager_load, :preload, :from, :readonly,
:having, :optimizer_hints, :with])

Instance Method Summary collapse

Instance Method Details

#_select!(*fields) ⇒ Object

:nodoc:



421
422
423
424
 
# File 'lib/active_record/relation/query_methods.rb', line 421

def _select!(*fields) # :nodoc:
  self.select_values |= fields
  self
end

#and(other) ⇒ Object

Returns a new relation, which is the logical intersection of this relation and the one passed as an argument.

The two relations must be structurally compatible: they must be scoping the same model, and they must differ only by #where (if no #group has been defined) or #having (if a #group is present).

Post.where(id: [1, 2]).and(Post.where(id: [2, 3]))
# SELECT `posts`.* FROM `posts` WHERE `posts`.`id` IN (1, 2) AND `posts`.`id` IN (2, 3)



1115
1116
1117
1118
1119
1120
1121
 
# File 'lib/active_record/relation/query_methods.rb', line 1115

def and(other)
  if other.is_a?(Relation)
    spawn.and!(other)
  else
    raise ArgumentError, "You have passed #{other.class.name} object to #and. Pass an ActiveRecord::Relation object instead."
  end
end

#and!(other) ⇒ Object

:nodoc:



1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
 
# File 'lib/active_record/relation/query_methods.rb', line 1123

def and!(other) # :nodoc:
  incompatible_values = structurally_incompatible_values_for(other)

  unless incompatible_values.empty?
    raise ArgumentError, "Relation passed to #and must be structurally compatible. Incompatible values: #{incompatible_values}"
  end

  self.where_clause |= other.where_clause
  self.having_clause |= other.having_clause
  self.references_values |= other.references_values

  self
end

#annotate(*args) ⇒ Object

Adds an SQL comment to queries generated from this relation. For example:

User.annotate("selecting user names").select(:name)
# SELECT "users"."name" FROM "users" /* selecting user names */

User.annotate("selecting", "user", "names").select(:name)
# SELECT "users"."name" FROM "users" /* selecting */ /* user */ /* names */

The SQL block comment delimiters, “/*” and “*/”, will be added automatically.

Some escaping is performed, however untrusted user input should not be used.



1509
1510
1511
1512
 
# File 'lib/active_record/relation/query_methods.rb', line 1509

def annotate(*args)
  check_if_method_has_arguments!(__callee__, args)
  spawn.annotate!(*args)
end

#annotate!(*args) ⇒ Object

Like #annotate, but modifies relation in place.



1515
1516
1517
1518
 
# File 'lib/active_record/relation/query_methods.rb', line 1515

def annotate!(*args) # :nodoc:
  self.annotate_values += args
  self
end

#arel(aliases = nil) ⇒ Object

Returns the Arel object associated with the relation.



1574
1575
1576
 
# File 'lib/active_record/relation/query_methods.rb', line 1574

def arel(aliases = nil) # :nodoc:
  @arel ||= with_connection { |c| build_arel(c, aliases) }
end

#construct_join_dependency(associations, join_type) ⇒ Object

:nodoc:



1578
1579
1580
1581
1582
 
# File 'lib/active_record/relation/query_methods.rb', line 1578

def construct_join_dependency(associations, join_type) # :nodoc:
  ActiveRecord::Associations::JoinDependency.new(
    klass, table, associations, join_type
  )
end

#create_with(value) ⇒ Object

Sets attributes to be used when creating new records from a relation object.

users = User.where(name: 'Oscar')
users.new.name # => 'Oscar'

users = users.create_with(name: 'DHH')
users.new.name # => 'DHH'

You can pass nil to #create_with to reset attributes:

users = users.create_with(nil)
users.new.name # => 'Oscar'



1326
1327
1328
 
# File 'lib/active_record/relation/query_methods.rb', line 1326

def create_with(value)
  spawn.create_with!(value)
end

#create_with!(value) ⇒ Object

:nodoc:



1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
 
# File 'lib/active_record/relation/query_methods.rb', line 1330

def create_with!(value) # :nodoc:
  if value
    value = sanitize_forbidden_attributes(value)
    self.create_with_value = create_with_value.merge(value)
  else
    self.create_with_value = FROZEN_EMPTY_HASH
  end

  self
end

#distinct(value = true) ⇒ Object

Specifies whether the records should be unique or not. For example:

User.select(:name)
# Might return two records with the same name

User.select(:name).distinct
# Returns 1 record per distinct name

User.select(:name).distinct.distinct(false)
# You can also remove the uniqueness



1390
1391
1392
 
# File 'lib/active_record/relation/query_methods.rb', line 1390

def distinct(value = true)
  spawn.distinct!(value)
end

#distinct!(value = true) ⇒ Object

Like #distinct, but modifies relation in place.



1395
1396
1397
1398
 
# File 'lib/active_record/relation/query_methods.rb', line 1395

def distinct!(value = true) # :nodoc:
  self.distinct_value = value
  self
end

#eager_load(*args) ⇒ Object

Specify associations args to be eager loaded using a LEFT OUTER JOIN. Performs a single query joining all specified associations. For example:

users = User.eager_load(:address).limit(5)
users.each do |user|
  user.address.city
end

# SELECT "users"."id" AS t0_r0, "users"."name" AS t0_r1, ... FROM "users"
#   LEFT OUTER JOIN "addresses" ON "addresses"."id" = "users"."address_id"
#   LIMIT 5

Instead of loading the 5 addresses with 5 separate queries, all addresses are loaded with a single joined query.

Loading multiple and nested associations is possible using Hashes and Arrays, similar to #includes:

User.eager_load(:address, friends: [:address, :followers])
# SELECT "users"."id" AS t0_r0, "users"."name" AS t0_r1, ... FROM "users"
#   LEFT OUTER JOIN "addresses" ON "addresses"."id" = "users"."address_id"
#   LEFT OUTER JOIN "friends" ON "friends"."user_id" = "users"."id"
#   ...

NOTE: Loading the associations in a join can result in many rows that contain redundant data and it performs poorly at scale.



283
284
285
286
 
# File 'lib/active_record/relation/query_methods.rb', line 283

def eager_load(*args)
  check_if_method_has_arguments!(__callee__, args)
  spawn.eager_load!(*args)
end

#eager_load!(*args) ⇒ Object

:nodoc:



288
289
290
291
 
# File 'lib/active_record/relation/query_methods.rb', line 288

def eager_load!(*args) # :nodoc:
  self.eager_load_values |= args
  self
end

#excluding(*records) ⇒ Object Also known as: without

Excludes the specified record (or collection of records) from the resulting relation. For example:

Post.excluding(post)
# SELECT "posts".* FROM "posts" WHERE "posts"."id" != 1

Post.excluding(post_one, post_two)
# SELECT "posts".* FROM "posts" WHERE "posts"."id" NOT IN (1, 2)

Post.excluding(Post.drafts)
# SELECT "posts".* FROM "posts" WHERE "posts"."id" NOT IN (3, 4, 5)

This can also be called on associations. As with the above example, either a single record of collection thereof may be specified:

post = Post.find(1)
comment = Comment.find(2)
post.comments.excluding(comment)
# SELECT "comments".* FROM "comments" WHERE "comments"."post_id" = 1 AND "comments"."id" != 2

This is short-hand for .where.not(id: post.id) and .where.not(id: [post_one.id, post_two.id]).

An ArgumentError will be raised if either no records are specified, or if any of the records in the collection (if a collection is passed in) are not instances of the same model that the relation is scoping.



1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
 
# File 'lib/active_record/relation/query_methods.rb', line 1554

def excluding(*records)
  relations = records.extract! { |element| element.is_a?(Relation) }
  records.flatten!(1)
  records.compact!

  unless records.all?(klass) && relations.all? { |relation| relation.klass == klass }
    raise ArgumentError, "You must only pass a single or collection of #{klass.name} objects to ##{__callee__}."
  end

  spawn.excluding!(records + relations.flat_map(&:ids))
end

#excluding!(records) ⇒ Object

:nodoc:



1567
1568
1569
1570
1571
 
# File 'lib/active_record/relation/query_methods.rb', line 1567

def excluding!(records) # :nodoc:
  predicates = [ predicate_builder[primary_key, records].invert ]
  self.where_clause += Relation::WhereClause.new(predicates)
  self
end

#extending(*modules, &block) ⇒ Object

Used to extend a scope with additional methods, either through a module or through a block provided.

The object returned is a relation, which can be further extended.

Using a Module

module Pagination
  def page(number)
    # pagination code goes here
  end
end

scope = Model.all.extending(Pagination)
scope.page(params[:page])

You can also pass a list of modules:

scope = Model.all.extending(Pagination, SomethingElse)

Using a Block

scope = Model.all.extending do
  def page(number)
    # pagination code goes here
  end
end
scope.page(params[:page])

You can also use a block and a module list:

scope = Model.all.extending(Pagination) do
  def per_page(number)
    # pagination code goes here
  end
end



1436
1437
1438
1439
1440
1441
1442
 
# File 'lib/active_record/relation/query_methods.rb', line 1436

def extending(*modules, &block)
  if modules.any? || block
    spawn.extending!(*modules, &block)
  else
    self
  end
end

#extending!(*modules, &block) ⇒ Object

:nodoc:



1444
1445
1446
1447
1448
1449
1450
1451
1452
 
# File 'lib/active_record/relation/query_methods.rb', line 1444

def extending!(*modules, &block) # :nodoc:
  modules << Module.new(&block) if block
  modules.flatten!

  self.extending_values += modules
  extend(*extending_values) if extending_values.any?

  self
end

#extract_associated(association) ⇒ Object

Extracts a named association from the relation. The named association is first preloaded, then the individual association records are collected from the relation. Like so:

.memberships.extract_associated(:user)
# => Returns collection of User records

This is short-hand for:

.memberships.preload(:user).collect(&:user)



334
335
336
 
# File 'lib/active_record/relation/query_methods.rb', line 334

def extract_associated(association)
  preload(association).collect(&association)
end

#from(value, subquery_name = nil) ⇒ Object

Specifies the table from which the records will be fetched. For example:

Topic.select('title').from('posts')
# SELECT title FROM posts

Can accept other relation objects. For example:

Topic.select('title').from(Topic.approved)
# SELECT title FROM (SELECT * FROM topics WHERE approved = 't') subquery

Passing a second argument (string or symbol), creates the alias for the SQL from clause. Otherwise the alias “subquery” is used:

Topic.select('a.title').from(Topic.approved, :a)
# SELECT a.title FROM (SELECT * FROM topics WHERE approved = 't') a

It does not add multiple arguments to the SQL from clause. The last from chained is the one used:

Topic.select('title').from(Topic.approved).from(Topic.inactive)
# SELECT title FROM (SELECT topics.* FROM topics WHERE topics.active = 'f') subquery

For multiple arguments for the SQL from clause, you can pass a string with the exact elements in the SQL from list:

color = "red"
Color
  .from("colors c, JSONB_ARRAY_ELEMENTS(colored_things) AS colorvalues(colorvalue)")
  .where("colorvalue->>'color' = ?", color)
  .select("c.*").to_a
# SELECT c.*
# FROM colors c, JSONB_ARRAY_ELEMENTS(colored_things) AS colorvalues(colorvalue)
# WHERE (colorvalue->>'color' = 'red')



1371
1372
1373
 
# File 'lib/active_record/relation/query_methods.rb', line 1371

def from(value, subquery_name = nil)
  spawn.from!(value, subquery_name)
end

#from!(value, subquery_name = nil) ⇒ Object

:nodoc:



1375
1376
1377
1378
 
# File 'lib/active_record/relation/query_methods.rb', line 1375

def from!(value, subquery_name = nil) # :nodoc:
  self.from_clause = Relation::FromClause.new(value, subquery_name)
  self
end

#group(*args) ⇒ Object

Allows to specify a group attribute:

User.group(:name)
# SELECT "users".* FROM "users" GROUP BY name

Returns an array with distinct records based on the group attribute:

User.select([:id, :name])
# => [#<User id: 1, name: "Oscar">, #<User id: 2, name: "Oscar">, #<User id: 3, name: "Foo">]

User.group(:name)
# => [#<User id: 3, name: "Foo", ...>, #<User id: 2, name: "Oscar", ...>]

User.group('name AS grouped_name, age')
# => [#<User id: 3, name: "Foo", age: 21, ...>, #<User id: 2, name: "Oscar", age: 21, ...>, #<User id: 5, name: "Foo", age: 23, ...>]

Passing in an array of attributes to group by is also supported.

User.select([:id, :first_name]).group(:id, :first_name).first(3)
# => [#<User id: 1, first_name: "Bill">, #<User id: 2, first_name: "Earl">, #<User id: 3, first_name: "Beto">]



566
567
568
569
 
# File 'lib/active_record/relation/query_methods.rb', line 566

def group(*args)
  check_if_method_has_arguments!(__callee__, args)
  spawn.group!(*args)
end

#group!(*args) ⇒ Object

:nodoc:



571
572
573
574
 
# File 'lib/active_record/relation/query_methods.rb', line 571

def group!(*args) # :nodoc:
  self.group_values += args
  self
end

#having(opts, *rest) ⇒ Object

Allows to specify a HAVING clause. Note that you can’t use HAVING without also specifying a GROUP clause.

Order.having('SUM(price) > 30').group('user_id')



1177
1178
1179
 
# File 'lib/active_record/relation/query_methods.rb', line 1177

def having(opts, *rest)
  opts.blank? ? self : spawn.having!(opts, *rest)
end

#having!(opts, *rest) ⇒ Object

:nodoc:



1181
1182
1183
1184
 
# File 'lib/active_record/relation/query_methods.rb', line 1181

def having!(opts, *rest) # :nodoc:
  self.having_clause += build_having_clause(opts, rest)
  self
end

#in_order_of(column, values) ⇒ Object

Applies an ORDER BY clause based on a given column, ordered and filtered by a specific set of values.

User.in_order_of(:id, [1, 5, 3])
# SELECT "users".* FROM "users"
#   WHERE "users"."id" IN (1, 5, 3)
#   ORDER BY CASE
#     WHEN "users"."id" = 1 THEN 1
#     WHEN "users"."id" = 5 THEN 2
#     WHEN "users"."id" = 3 THEN 3
#   END ASC

column can point to an enum column; the actual query generated may be different depending on the database adapter and the column definition.

class Conversation < ActiveRecord::Base
  enum :status, [ :active, :archived ]
end

Conversation.in_order_of(:status, [:archived, :active])
# SELECT "conversations".* FROM "conversations"
#   WHERE "conversations"."status" IN (1, 0)
#   ORDER BY CASE
#     WHEN "conversations"."status" = 1 THEN 1
#     WHEN "conversations"."status" = 0 THEN 2
#   END ASC

values can also include nil.

Conversation.in_order_of(:status, [nil, :archived, :active])
# SELECT "conversations".* FROM "conversations"
#   WHERE ("conversations"."status" IN (1, 0) OR "conversations"."status" IS NULL)
#   ORDER BY CASE
#     WHEN "conversations"."status" IS NULL THEN 1
#     WHEN "conversations"."status" = 1 THEN 2
#     WHEN "conversations"."status" = 0 THEN 3
#   END ASC



701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
 
# File 'lib/active_record/relation/query_methods.rb', line 701

def in_order_of(column, values)
  klass.disallow_raw_sql!([column], permit: model.adapter_class.column_name_with_order_matcher)
  return spawn.none! if values.empty?

  references = column_references([column])
  self.references_values |= references unless references.empty?

  values = values.map { |value| type_caster.type_cast_for_database(column, value) }
  arel_column = column.is_a?(Arel::Nodes::SqlLiteral) ? column : order_column(column.to_s)

  where_clause =
    if values.include?(nil)
      arel_column.in(values.compact).or(arel_column.eq(nil))
    else
      arel_column.in(values)
    end

  spawn
    .order!(build_case_for_value_position(arel_column, values))
    .where!(where_clause)
end

#includes(*args) ⇒ Object

Specify associations args to be eager loaded to prevent N + 1 queries. A separate query is performed for each association, unless a join is required by conditions.

For example:

users = User.includes(:address).limit(5)
users.each do |user|
  user.address.city
end

# SELECT "users".* FROM "users" LIMIT 5
# SELECT "addresses".* FROM "addresses" WHERE "addresses"."id" IN (1,2,3,4,5)

Instead of loading the 5 addresses with 5 separate queries, all addresses are loaded with a single query.

Loading the associations in a separate query will often result in a performance improvement over a simple join, as a join can result in many rows that contain redundant data and it performs poorly at scale.

You can also specify multiple associations. Each association will result in an additional query:

User.includes(:address, :friends).to_a
# SELECT "users".* FROM "users"
# SELECT "addresses".* FROM "addresses" WHERE "addresses"."id" IN (1,2,3,4,5)
# SELECT "friends".* FROM "friends" WHERE "friends"."user_id" IN (1,2,3,4,5)

Loading nested associations is possible using a Hash:

User.includes(:address, friends: [:address, :followers])

Conditions

If you want to add string conditions to your included models, you’ll have to explicitly reference them. For example:

User.includes(:posts).where('posts.name = ?', 'example').to_a

Will throw an error, but this will work:

User.includes(:posts).where('posts.name = ?', 'example').references(:posts).to_a
# SELECT "users"."id" AS t0_r0, ... FROM "users"
#   LEFT OUTER JOIN "posts" ON "posts"."user_id" = "users"."id"
#   WHERE "posts"."name" = ?  [["name", "example"]]

As the LEFT OUTER JOIN already contains the posts, the second query for the posts is no longer performed.

Note that #includes works with association names while #references needs the actual table name.

If you pass the conditions via a Hash, you don’t need to call #references explicitly, as #where references the tables for you. For example, this will work correctly:

User.includes(:posts).where(posts: { name: 'example' })

NOTE: Conditions affect both sides of an association. For example, the above code will return only users that have a post named “example”, and will only include posts named “example”, even when a matching user has other additional posts.



247
248
249
250
 
# File 'lib/active_record/relation/query_methods.rb', line 247

def includes(*args)
  check_if_method_has_arguments!(__callee__, args)
  spawn.includes!(*args)
end

#includes!(*args) ⇒ Object

:nodoc:



252
253
254
255
 
# File 'lib/active_record/relation/query_methods.rb', line 252

def includes!(*args) # :nodoc:
  self.includes_values |= args
  self
end

#invert_where ⇒ Object

Allows you to invert an entire where clause instead of manually applying conditions.

class User
  scope :active, -> { where(accepted: true, locked: false) }
end

User.where(accepted: true)
# WHERE `accepted` = 1

User.where(accepted: true).invert_where
# WHERE `accepted` != 1

User.active
# WHERE `accepted` = 1 AND `locked` = 0

User.active.invert_where
# WHERE NOT (`accepted` = 1 AND `locked` = 0)

Be careful because this inverts all conditions before invert_where call.

class User
  scope :active, -> { where(accepted: true, locked: false) }
  scope :inactive, -> { active.invert_where } # Do not attempt it
end

# It also inverts `where(role: 'admin')` unexpectedly.
User.where(role: 'admin').inactive
# WHERE NOT (`role` = 'admin' AND `accepted` = 1 AND `locked` = 0)



1081
1082
1083
 
# File 'lib/active_record/relation/query_methods.rb', line 1081

def invert_where
  spawn.invert_where!
end

#invert_where! ⇒ Object

:nodoc:



1085
1086
1087
1088
 
# File 'lib/active_record/relation/query_methods.rb', line 1085

def invert_where! # :nodoc:
  self.where_clause = where_clause.invert
  self
end

#joins(*args) ⇒ Object

Performs JOINs on args. The given symbol(s) should match the name of the association(s).

User.joins(:posts)
# SELECT "users".*
# FROM "users"
# INNER JOIN "posts" ON "posts"."user_id" = "users"."id"

Multiple joins:

User.joins(:posts, :account)
# SELECT "users".*
# FROM "users"
# INNER JOIN "posts" ON "posts"."user_id" = "users"."id"
# INNER JOIN "accounts" ON "accounts"."id" = "users"."account_id"

Nested joins:

User.joins(posts: [:comments])
# SELECT "users".*
# FROM "users"
# INNER JOIN "posts" ON "posts"."user_id" = "users"."id"
# INNER JOIN "comments" ON "comments"."post_id" = "posts"."id"

You can use strings in order to customize your joins:

User.joins("LEFT JOIN bookmarks ON bookmarks.bookmarkable_type = 'Post' AND bookmarks.user_id = users.id")
# SELECT "users".* FROM "users" LEFT JOIN bookmarks ON bookmarks.bookmarkable_type = 'Post' AND bookmarks.user_id = users.id



848
849
850
851
 
# File 'lib/active_record/relation/query_methods.rb', line 848

def joins(*args)
  check_if_method_has_arguments!(__callee__, args)
  spawn.joins!(*args)
end

#joins!(*args) ⇒ Object

:nodoc:



853
854
855
856
 
# File 'lib/active_record/relation/query_methods.rb', line 853

def joins!(*args) # :nodoc:
  self.joins_values |= args
  self
end

#left_outer_joins(*args) ⇒ Object Also known as: left_joins

Performs LEFT OUTER JOINs on args:

User.left_outer_joins(:posts)
# SELECT "users".* FROM "users" LEFT OUTER JOIN "posts" ON "posts"."user_id" = "users"."id"



863
864
865
866
 
# File 'lib/active_record/relation/query_methods.rb', line 863

def left_outer_joins(*args)
  check_if_method_has_arguments!(__callee__, args)
  spawn.left_outer_joins!(*args)
end

#left_outer_joins!(*args) ⇒ Object

:nodoc:



869
870
871
872
 
# File 'lib/active_record/relation/query_methods.rb', line 869

def left_outer_joins!(*args) # :nodoc:
  self.left_outer_joins_values |= args
  self
end

#limit(value) ⇒ Object

Specifies a limit for the number of records to retrieve.

User.limit(10) # generated SQL has 'LIMIT 10'

User.limit(10).limit(20) # generated SQL has 'LIMIT 20'



1191
1192
1193
 
# File 'lib/active_record/relation/query_methods.rb', line 1191

def limit(value)
  spawn.limit!(value)
end

#limit!(value) ⇒ Object

:nodoc:



1195
1196
1197
1198
 
# File 'lib/active_record/relation/query_methods.rb', line 1195

def limit!(value) # :nodoc:
  self.limit_value = value
  self
end

#lock(locks = true) ⇒ Object

Specifies locking settings (default to true). For more information on locking, please see ActiveRecord::Locking.



1218
1219
1220
 
# File 'lib/active_record/relation/query_methods.rb', line 1218

def lock(locks = true)
  spawn.lock!(locks)
end

#lock!(locks = true) ⇒ Object

:nodoc:



1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
 
# File 'lib/active_record/relation/query_methods.rb', line 1222

def lock!(locks = true) # :nodoc:
  case locks
  when String, TrueClass, NilClass
    self.lock_value = locks || true
  else
    self.lock_value = false
  end

  self
end

#none ⇒ Object

Returns a chainable relation with zero records.

The returned relation implements the Null Object pattern. It is an object with defined null behavior and always returns an empty array of records without querying the database.

Any subsequent condition chained to the returned relation will continue generating an empty relation and will not fire any query to the database.

Used in cases where a method or scope could return zero records but the result needs to be chainable.

For example:

@posts = current_user.visible_posts.where(name: params[:name])
# the visible_posts method is expected to return a chainable Relation

def visible_posts
  case role
  when 'Country Manager'
    Post.where(country: country)
  when 'Reviewer'
    Post.published
  when 'Bad User'
    Post.none # It can't be chained if [] is returned.
  end
end



1261
1262
1263
 
# File 'lib/active_record/relation/query_methods.rb', line 1261

def none
  spawn.none!
end

#none! ⇒ Object

:nodoc:



1265
1266
1267
1268
1269
1270
1271
 
# File 'lib/active_record/relation/query_methods.rb', line 1265

def none! # :nodoc:
  unless @none
    where!("1=0")
    @none = true
  end
  self
end

#null_relation? ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


1273
1274
1275
 
# File 'lib/active_record/relation/query_methods.rb', line 1273

def null_relation? # :nodoc:
  @none
end

#offset(value) ⇒ Object

Specifies the number of rows to skip before returning rows.

User.offset(10) # generated SQL has "OFFSET 10"

Should be used with order.

User.offset(10).order("name ASC")



1207
1208
1209
 
# File 'lib/active_record/relation/query_methods.rb', line 1207

def offset(value)
  spawn.offset!(value)
end

#offset!(value) ⇒ Object

:nodoc:



1211
1212
1213
1214
 
# File 'lib/active_record/relation/query_methods.rb', line 1211

def offset!(value) # :nodoc:
  self.offset_value = value
  self
end

#optimizer_hints(*args) ⇒ Object

Specify optimizer hints to be used in the SELECT statement.

Example (for MySQL):

Topic.optimizer_hints("MAX_EXECUTION_TIME(50000)", "NO_INDEX_MERGE(topics)")
# SELECT /*+ MAX_EXECUTION_TIME(50000) NO_INDEX_MERGE(topics) */ `topics`.* FROM `topics`

Example (for PostgreSQL with pg_hint_plan):

Topic.optimizer_hints("SeqScan(topics)", "Parallel(topics 8)")
# SELECT /*+ SeqScan(topics) Parallel(topics 8) */ "topics".* FROM "topics"



1465
1466
1467
1468
 
# File 'lib/active_record/relation/query_methods.rb', line 1465

def optimizer_hints(*args)
  check_if_method_has_arguments!(__callee__, args)
  spawn.optimizer_hints!(*args)
end

#optimizer_hints!(*args) ⇒ Object

:nodoc:



1470
1471
1472
1473
 
# File 'lib/active_record/relation/query_methods.rb', line 1470

def optimizer_hints!(*args) # :nodoc:
  self.optimizer_hints_values |= args
  self
end

#or(other) ⇒ Object

Returns a new relation, which is the logical union of this relation and the one passed as an argument.

The two relations must be structurally compatible: they must be scoping the same model, and they must differ only by #where (if no #group has been defined) or #having (if a #group is present).

Post.where("id = 1").or(Post.where("author_id = 3"))
# SELECT `posts`.* FROM `posts` WHERE ((id = 1) OR (author_id = 3))



1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
 
# File 'lib/active_record/relation/query_methods.rb', line 1147

def or(other)
  if other.is_a?(Relation)
    if @none
      other.spawn
    else
      spawn.or!(other)
    end
  else
    raise ArgumentError, "You have passed #{other.class.name} object to #or. Pass an ActiveRecord::Relation object instead."
  end
end

#or!(other) ⇒ Object

:nodoc:



1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
 
# File 'lib/active_record/relation/query_methods.rb', line 1159

def or!(other) # :nodoc:
  incompatible_values = structurally_incompatible_values_for(other)

  unless incompatible_values.empty?
    raise ArgumentError, "Relation passed to #or must be structurally compatible. Incompatible values: #{incompatible_values}"
  end

  self.where_clause = where_clause.or(other.where_clause)
  self.having_clause = having_clause.or(other.having_clause)
  self.references_values |= other.references_values

  self
end

#order(*args) ⇒ Object

Applies an ORDER BY clause to a query.

#order accepts arguments in one of several formats.

symbols

The symbol represents the name of the column you want to order the results by.

User.order(:name)
# SELECT "users".* FROM "users" ORDER BY "users"."name" ASC

By default, the order is ascending. If you want descending order, you can map the column name symbol to :desc.

User.order(email: :desc)
# SELECT "users".* FROM "users" ORDER BY "users"."email" DESC

Multiple columns can be passed this way, and they will be applied in the order specified.

User.order(:name, email: :desc)
# SELECT "users".* FROM "users" ORDER BY "users"."name" ASC, "users"."email" DESC

strings

Strings are passed directly to the database, allowing you to specify simple SQL expressions.

This could be a source of SQL injection, so only strings composed of plain column names and simple function(column_name) expressions with optional ASC/DESC modifiers are allowed.

User.order('name')
# SELECT "users".* FROM "users" ORDER BY name

User.order('name DESC')
# SELECT "users".* FROM "users" ORDER BY name DESC

User.order('name DESC, email')
# SELECT "users".* FROM "users" ORDER BY name DESC, email

Arel

If you need to pass in complicated expressions that you have verified are safe for the database, you can use Arel.

User.order(Arel.sql('end_date - start_date'))
# SELECT "users".* FROM "users" ORDER BY end_date - start_date

Custom query syntax, like JSON columns for PostgreSQL, is supported in this way.

User.order(Arel.sql("payload->>'kind'"))
# SELECT "users".* FROM "users" ORDER BY payload->>'kind'



649
650
651
652
653
654
 
# File 'lib/active_record/relation/query_methods.rb', line 649

def order(*args)
  check_if_method_has_arguments!(__callee__, args) do
    sanitize_order_arguments(args)
  end
  spawn.order!(*args)
end

#order!(*args) ⇒ Object

Same as #order but operates on relation in-place instead of copying.



657
658
659
660
661
 
# File 'lib/active_record/relation/query_methods.rb', line 657

def order!(*args) # :nodoc:
  preprocess_order_args(args) unless args.empty?
  self.order_values |= args
  self
end

#preload(*args) ⇒ Object

Specify associations args to be eager loaded using separate queries. A separate query is performed for each association.

users = User.preload(:address).limit(5)
users.each do |user|
  user.address.city
end

# SELECT "users".* FROM "users" LIMIT 5
# SELECT "addresses".* FROM "addresses" WHERE "addresses"."id" IN (1,2,3,4,5)

Instead of loading the 5 addresses with 5 separate queries, all addresses are loaded with a separate query.

Loading multiple and nested associations is possible using Hashes and Arrays, similar to #includes:

User.preload(:address, friends: [:address, :followers])
# SELECT "users".* FROM "users"
# SELECT "addresses".* FROM "addresses" WHERE "addresses"."id" IN (1,2,3,4,5)
# SELECT "friends".* FROM "friends" WHERE "friends"."user_id" IN (1,2,3,4,5)
# SELECT ...



315
316
317
318
 
# File 'lib/active_record/relation/query_methods.rb', line 315

def preload(*args)
  check_if_method_has_arguments!(__callee__, args)
  spawn.preload!(*args)
end

#preload!(*args) ⇒ Object

:nodoc:



320
321
322
323
 
# File 'lib/active_record/relation/query_methods.rb', line 320

def preload!(*args) # :nodoc:
  self.preload_values |= args
  self
end

#readonly(value = true) ⇒ Object

Mark a relation as readonly. Attempting to update a record will result in an error.

users = User.readonly
users.first.save
# => ActiveRecord::ReadOnlyRecord: User is marked as readonly

To make a readonly relation writable, pass false.

users.readonly(false)
users.first.save
# => true



1289
1290
1291
 
# File 'lib/active_record/relation/query_methods.rb', line 1289

def readonly(value = true)
  spawn.readonly!(value)
end

#readonly!(value = true) ⇒ Object

:nodoc:



1293
1294
1295
1296
 
# File 'lib/active_record/relation/query_methods.rb', line 1293

def readonly!(value = true) # :nodoc:
  self.readonly_value = value
  self
end

#references(*table_names) ⇒ Object

Use to indicate that the given table_names are referenced by an SQL string, and should therefore be JOINed in any query rather than loaded separately. This method only works in conjunction with #includes. See #includes for more details.

User.includes(:posts).where("posts.name = 'foo'")
# Doesn't JOIN the posts table, resulting in an error.

User.includes(:posts).where("posts.name = 'foo'").references(:posts)
# Query now knows the string references posts, so adds a JOIN



348
349
350
351
 
# File 'lib/active_record/relation/query_methods.rb', line 348

def references(*table_names)
  check_if_method_has_arguments!(__callee__, table_names)
  spawn.references!(*table_names)
end

#references!(*table_names) ⇒ Object

:nodoc:



353
354
355
356
 
# File 'lib/active_record/relation/query_methods.rb', line 353

def references!(*table_names) # :nodoc:
  self.references_values |= table_names
  self
end

#regroup(*args) ⇒ Object

Allows you to change a previously set group statement.

Post.group(:title, :body)
# SELECT `posts`.`*` FROM `posts` GROUP BY `posts`.`title`, `posts`.`body`

Post.group(:title, :body).regroup(:title)
# SELECT `posts`.`*` FROM `posts` GROUP BY `posts`.`title`

This is short-hand for unscope(:group).group(fields). Note that we’re unscoping the entire group statement.



586
587
588
589
 
# File 'lib/active_record/relation/query_methods.rb', line 586

def regroup(*args)
  check_if_method_has_arguments!(__callee__, args)
  spawn.regroup!(*args)
end

#regroup!(*args) ⇒ Object

Same as #regroup but operates on relation in-place instead of copying.



592
593
594
595
 
# File 'lib/active_record/relation/query_methods.rb', line 592

def regroup!(*args) # :nodoc:
  self.group_values = args
  self
end

#reorder(*args) ⇒ Object

Replaces any existing order defined on the relation with the specified order.

User.order('email DESC').reorder('id ASC') # generated SQL has 'ORDER BY id ASC'

Subsequent calls to order on the same relation will be appended. For example:

User.order('email DESC').reorder('id ASC').order('name ASC')

generates a query with ORDER BY id ASC, name ASC.



732
733
734
735
736
737
 
# File 'lib/active_record/relation/query_methods.rb', line 732

def reorder(*args)
  check_if_method_has_arguments!(__callee__, args) do
    sanitize_order_arguments(args)
  end
  spawn.reorder!(*args)
end

#reorder!(*args) ⇒ Object

Same as #reorder but operates on relation in-place instead of copying.



740
741
742
743
744
745
746
 
# File 'lib/active_record/relation/query_methods.rb', line 740

def reorder!(*args) # :nodoc:
  preprocess_order_args(args)
  args.uniq!
  self.reordering_value = true
  self.order_values = args
  self
end

#reselect(*args) ⇒ Object

Allows you to change a previously set select statement.

Post.select(:title, :body)
# SELECT `posts`.`title`, `posts`.`body` FROM `posts`

Post.select(:title, :body).reselect(:created_at)
# SELECT `posts`.`created_at` FROM `posts`

This is short-hand for unscope(:select).select(fields). Note that we’re unscoping the entire select statement.



534
535
536
537
538
 
# File 'lib/active_record/relation/query_methods.rb', line 534

def reselect(*args)
  check_if_method_has_arguments!(__callee__, args)
  args = process_select_args(args)
  spawn.reselect!(*args)
end

#reselect!(*args) ⇒ Object

Same as #reselect but operates on relation in-place instead of copying.



541
542
543
544
 
# File 'lib/active_record/relation/query_methods.rb', line 541

def reselect!(*args) # :nodoc:
  self.select_values = args
  self
end

#reverse_order ⇒ Object

Reverse the existing order clause on the relation.

User.order('name ASC').reverse_order # generated SQL has 'ORDER BY name DESC'



1478
1479
1480
 
# File 'lib/active_record/relation/query_methods.rb', line 1478

def reverse_order
  spawn.reverse_order!
end

#reverse_order! ⇒ Object

:nodoc:



1482
1483
1484
1485
1486
 
# File 'lib/active_record/relation/query_methods.rb', line 1482

def reverse_order! # :nodoc:
  orders = order_values.compact_blank
  self.order_values = reverse_sql_order(orders)
  self
end

#rewhere(conditions) ⇒ Object

Allows you to change a previously set where condition for a given attribute, instead of appending to that condition.

Post.where(trashed: true).where(trashed: false)
# WHERE `trashed` = 1 AND `trashed` = 0

Post.where(trashed: true).rewhere(trashed: false)
# WHERE `trashed` = 0

Post.where(active: true).where(trashed: true).rewhere(trashed: false)
# WHERE `active` = 1 AND `trashed` = 0

This is short-hand for unscope(where: conditions.keys).where(conditions). Note that unlike reorder, we’re only unscoping the named conditions – not the entire where statement.



1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
 
# File 'lib/active_record/relation/query_methods.rb', line 1041

def rewhere(conditions)
  return unscope(:where) if conditions.nil?

  scope = spawn
  where_clause = scope.build_where_clause(conditions)

  scope.unscope!(where: where_clause.extract_attributes)
  scope.where_clause += where_clause
  scope
end

#select(*fields) ⇒ Object

Works in two unique ways.

First: takes a block so it can be used just like Array#select.

Model.all.select { |m| m.field == value }

This will build an array of objects from the database for the scope, converting them into an array and iterating through them using Array#select.

Second: Modifies the SELECT statement for the query so that only certain fields are retrieved:

Model.select(:field)
# => [#<Model id: nil, field: "value">]

Although in the above example it looks as though this method returns an array, it actually returns a relation object and can have other query methods appended to it, such as the other methods in ActiveRecord::QueryMethods.

The argument to the method can also be an array of fields.

Model.select(:field, :other_field, :and_one_more)
# => [#<Model id: nil, field: "value", other_field: "value", and_one_more: "value">]

The argument also can be a hash of fields and aliases.

Model.select(models: { field: :alias, other_field: :other_alias })
# => [#<Model id: nil, alias: "value", other_alias: "value">]

Model.select(models: [:field, :other_field])
# => [#<Model id: nil, field: "value", other_field: "value">]

You can also use one or more strings, which will be used unchanged as SELECT fields.

Model.select('field AS field_one', 'other_field AS field_two')
# => [#<Model id: nil, field_one: "value", field_two: "value">]

If an alias was specified, it will be accessible from the resulting objects:

Model.select('field AS field_one').first.field_one
# => "value"

Accessing attributes of an object that do not have fields retrieved by a select except id will throw ActiveModel::MissingAttributeError:

Model.select(:field).first.other_field
# => ActiveModel::MissingAttributeError: missing attribute 'other_field' for Model



406
407
408
409
410
411
412
413
414
415
416
417
418
419
 
# File 'lib/active_record/relation/query_methods.rb', line 406

def select(*fields)
  if block_given?
    if fields.any?
      raise ArgumentError, "`select' with block doesn't take arguments."
    end

    return super()
  end

  check_if_method_has_arguments!(__callee__, fields, "Call `select' with at least one field.")

  fields = process_select_args(fields)
  spawn._select!(*fields)
end

#skip_preloading! ⇒ Object

:nodoc:



1493
1494
1495
1496
 
# File 'lib/active_record/relation/query_methods.rb', line 1493

def skip_preloading! # :nodoc:
  self.skip_preloading_value = true
  self
end

#skip_query_cache!(value = true) ⇒ Object

:nodoc:



1488
1489
1490
1491
 
# File 'lib/active_record/relation/query_methods.rb', line 1488

def skip_query_cache!(value = true) # :nodoc:
  self.skip_query_cache_value = value
  self
end

#strict_loading(value = true) ⇒ Object

Sets the returned relation to strict_loading mode. This will raise an error if the record tries to lazily load an association.

user = User.strict_loading.first
user.comments.to_a
# => ActiveRecord::StrictLoadingViolationError



1304
1305
1306
 
# File 'lib/active_record/relation/query_methods.rb', line 1304

def strict_loading(value = true)
  spawn.strict_loading!(value)
end

#strict_loading!(value = true) ⇒ Object

:nodoc:



1308
1309
1310
1311
 
# File 'lib/active_record/relation/query_methods.rb', line 1308

def strict_loading!(value = true) # :nodoc:
  self.strict_loading_value = value
  self
end

#structurally_compatible?(other) ⇒ Boolean

Checks whether the given relation is structurally compatible with this relation, to determine if it’s possible to use the #and and #or methods without raising an error. Structurally compatible is defined as: they must be scoping the same model, and they must differ only by #where (if no #group has been defined) or #having (if a #group is present).

Post.where("id = 1").structurally_compatible?(Post.where("author_id = 3"))
# => true

Post.joins(:comments).structurally_compatible?(Post.where("id = 1"))
# => false

Returns:

  • (Boolean) 


1101
1102
1103
 
# File 'lib/active_record/relation/query_methods.rb', line 1101

def structurally_compatible?(other)
  structurally_incompatible_values_for(other).empty?
end

#uniq!(name) ⇒ Object

Deduplicate multiple values.



1521
1522
1523
1524
1525
1526
 
# File 'lib/active_record/relation/query_methods.rb', line 1521

def uniq!(name)
  if values = @values[name]
    values.uniq! if values.is_a?(Array) && !values.empty?
  end
  self
end

#unscope(*args) ⇒ Object

Removes an unwanted relation that is already defined on a chain of relations. This is useful when passing around chains of relations and would like to modify the relations without reconstructing the entire chain.

User.order('email DESC').unscope(:order) == User.all

The method arguments are symbols which correspond to the names of the methods which should be unscoped. The valid arguments are given in VALID_UNSCOPING_VALUES. The method can also be called with multiple arguments. For example:

User.order('email DESC').select('id').where(name: "John")
    .unscope(:order, :select, :where) == User.all

One can additionally pass a hash as an argument to unscope specific :where values. This is done by passing a hash with a single key-value pair. The key should be :where and the value should be the where value to unscope. For example:

User.where(name: "John", active: true).unscope(where: :name)
    == User.where(active: true)

This method is similar to #except, but unlike #except, it persists across merges:

User.order('email').merge(User.except(:order))
    == User.order('email')

User.order('email').merge(User.unscope(:order))
    == User.all

This means it can be used in association definitions:

has_many :comments, -> { unscope(where: :trashed) }



786
787
788
789
 
# File 'lib/active_record/relation/query_methods.rb', line 786

def unscope(*args)
  check_if_method_has_arguments!(__callee__, args)
  spawn.unscope!(*args)
end

#unscope!(*args) ⇒ Object

:nodoc:



791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
 
# File 'lib/active_record/relation/query_methods.rb', line 791

def unscope!(*args) # :nodoc:
  self.unscope_values += args

  args.each do |scope|
    case scope
    when Symbol
      scope = :left_outer_joins if scope == :left_joins
      if !VALID_UNSCOPING_VALUES.include?(scope)
        raise ArgumentError, "Called unscope() with invalid unscoping argument ':#{scope}'. Valid arguments are :#{VALID_UNSCOPING_VALUES.to_a.join(", :")}."
      end
      assert_modifiable!
      @values.delete(scope)
    when Hash
      scope.each do |key, target_value|
        if key != :where
          raise ArgumentError, "Hash arguments in .unscope(*args) must have :where as the key."
        end

        target_values = resolve_arel_attributes(Array.wrap(target_value))
        self.where_clause = where_clause.except(*target_values)
      end
    else
      raise ArgumentError, "Unrecognized scoping: #{args.inspect}. Use .unscope(where: :attribute_name) or .unscope(:order), for example."
    end
  end

  self
end

#where(*args) ⇒ Object

Returns a new relation, which is the result of filtering the current relation according to the conditions in the arguments.

#where accepts conditions in one of several formats. In the examples below, the resulting SQL is given as an illustration; the actual query generated may be different depending on the database adapter.

String

A single string, without additional arguments, is passed to the query constructor as an SQL fragment, and used in the where clause of the query.

Client.where("orders_count = '2'")
# SELECT * from clients where orders_count = '2';

Note that building your own string from user input may expose your application to injection attacks if not done properly. As an alternative, it is recommended to use one of the following methods.

Array

If an array is passed, then the first element of the array is treated as a template, and the remaining elements are inserted into the template to generate the condition. Active Record takes care of building the query to avoid injection attacks, and will convert from the ruby type to the database type where needed. Elements are inserted into the string in the order in which they appear.

User.where(["name = ? and email = ?", "Joe", "[email protected]"])
# SELECT * FROM users WHERE name = 'Joe' AND email = '[email protected]';

Alternatively, you can use named placeholders in the template, and pass a hash as the second element of the array. The names in the template are replaced with the corresponding values from the hash.

User.where(["name = :name and email = :email", { name: "Joe", email: "[email protected]" }])
# SELECT * FROM users WHERE name = 'Joe' AND email = '[email protected]';

This can make for more readable code in complex queries.

Lastly, you can use sprintf-style % escapes in the template. This works slightly differently than the previous methods; you are responsible for ensuring that the values in the template are properly quoted. The values are passed to the connector for quoting, but the caller is responsible for ensuring they are enclosed in quotes in the resulting SQL. After quoting, the values are inserted using the same escapes as the Ruby core method Kernel::sprintf.

User.where(["name = '%s' and email = '%s'", "Joe", "[email protected]"])
# SELECT * FROM users WHERE name = 'Joe' AND email = '[email protected]';

If #where is called with multiple arguments, these are treated as if they were passed as the elements of a single array.

User.where("name = :name and email = :email", { name: "Joe", email: "[email protected]" })
# SELECT * FROM users WHERE name = 'Joe' AND email = '[email protected]';

When using strings to specify conditions, you can use any operator available from the database. While this provides the most flexibility, you can also unintentionally introduce dependencies on the underlying database. If your code is intended for general consumption, test with multiple database backends.

Hash

#where will also accept a hash condition, in which the keys are fields and the values are values to be searched for.

Fields can be symbols or strings. Values can be single values, arrays, or ranges.

User.where(name: "Joe", email: "[email protected]")
# SELECT * FROM users WHERE name = 'Joe' AND email = '[email protected]'

User.where(name: ["Alice", "Bob"])
# SELECT * FROM users WHERE name IN ('Alice', 'Bob')

User.where(created_at: (Time.now.midnight - 1.day)..Time.now.midnight)
# SELECT * FROM users WHERE (created_at BETWEEN '2012-06-09 07:00:00.000000' AND '2012-06-10 07:00:00.000000')

In the case of a belongs_to relationship, an association key can be used to specify the model if an ActiveRecord object is used as the value.

author = Author.find(1)

# The following queries will be equivalent:
Post.where(author: author)
Post.where(author_id: author)

This also works with polymorphic belongs_to relationships:

treasure = Treasure.create(name: 'gold coins')
treasure.price_estimates << PriceEstimate.create(price: 125)

# The following queries will be equivalent:
PriceEstimate.where(estimate_of: treasure)
PriceEstimate.where(estimate_of_type: 'Treasure', estimate_of_id: treasure)

Hash conditions may also be specified in a tuple-like syntax. Hash keys may be an array of columns with an array of tuples as values.

Article.where([:author_id, :id] => [[15, 1], [15, 2]])
# SELECT * FROM articles WHERE author_id = 15 AND id = 1 OR author_id = 15 AND id = 2

Joins

If the relation is the result of a join, you may create a condition which uses any of the tables in the join. For string and array conditions, use the table name in the condition.

User.joins(:posts).where("posts.created_at < ?", Time.now)

For hash conditions, you can either use the table name in the key, or use a sub-hash.

User.joins(:posts).where("posts.published" => true)
User.joins(:posts).where(posts: { published: true })

No Argument

If no argument is passed, #where returns a new instance of WhereChain, that can be chained with WhereChain#not, WhereChain#missing, or WhereChain#associated.

Chaining with WhereChain#not:

User.where.not(name: "Jon")
# SELECT * FROM users WHERE name != 'Jon'

Chaining with WhereChain#associated:

Post.where.associated(:author)
# SELECT "posts".* FROM "posts"
# INNER JOIN "authors" ON "authors"."id" = "posts"."author_id"
# WHERE "authors"."id" IS NOT NULL

Chaining with WhereChain#missing:

Post.where.missing(:author)
# SELECT "posts".* FROM "posts"
# LEFT OUTER JOIN "authors" ON "authors"."id" = "posts"."author_id"
# WHERE "authors"."id" IS NULL

Blank Condition

If the condition is any blank-ish object, then #where is a no-op and returns the current relation.



1013
1014
1015
1016
1017
1018
1019
1020
1021
 
# File 'lib/active_record/relation/query_methods.rb', line 1013

def where(*args)
  if args.empty?
    WhereChain.new(spawn)
  elsif args.length == 1 && args.first.blank?
    self
  else
    spawn.where!(*args)
  end
end

#where!(opts, *rest) ⇒ Object

:nodoc:



1023
1024
1025
1026
 
# File 'lib/active_record/relation/query_methods.rb', line 1023

def where!(opts, *rest) # :nodoc:
  self.where_clause += build_where_clause(opts, rest)
  self
end

#with(*args) ⇒ Object

Add a Common Table Expression (CTE) that you can then reference within another SELECT statement.

Note: CTE’s are only supported in MySQL for versions 8.0 and above. You will not be able to use CTE’s with MySQL 5.7.

Post.with(posts_with_tags: Post.where("tags_count > ?", 0))
# => ActiveRecord::Relation
# WITH posts_with_tags AS (
#   SELECT * FROM posts WHERE (tags_count > 0)
# )
# SELECT * FROM posts

You can also pass an array of sub-queries to be joined in a UNION ALL.

Post.with(posts_with_tags_or_comments: [Post.where("tags_count > ?", 0), Post.where("comments_count > ?", 0)])
# => ActiveRecord::Relation
# WITH posts_with_tags_or_comments AS (
#  (SELECT * FROM posts WHERE (tags_count > 0))
#  UNION ALL
#  (SELECT * FROM posts WHERE (comments_count > 0))
# )
# SELECT * FROM posts

Once you define Common Table Expression you can use custom FROM value or JOIN to reference it.

Post.with(posts_with_tags: Post.where("tags_count > ?", 0)).from("posts_with_tags AS posts")
# => ActiveRecord::Relation
# WITH posts_with_tags AS (
#  SELECT * FROM posts WHERE (tags_count > 0)
# )
# SELECT * FROM posts_with_tags AS posts

Post.with(posts_with_tags: Post.where("tags_count > ?", 0)).joins("JOIN posts_with_tags ON posts_with_tags.id = posts.id")
# => ActiveRecord::Relation
# WITH posts_with_tags AS (
#   SELECT * FROM posts WHERE (tags_count > 0)
# )
# SELECT * FROM posts JOIN posts_with_tags ON posts_with_tags.id = posts.id

It is recommended to pass a query as ActiveRecord::Relation. If that is not possible and you have verified it is safe for the database, you can pass it as SQL literal using Arel.

Post.with(popular_posts: Arel.sql("... complex sql to calculate posts popularity ..."))

Great caution should be taken to avoid SQL injection vulnerabilities. This method should not be used with unsafe values that include unsanitized input.

To add multiple CTEs just pass multiple key-value pairs

Post.with(
  posts_with_comments: Post.where("comments_count > ?", 0),
  posts_with_tags: Post.where("tags_count > ?", 0)
)

or chain multiple .with calls

Post
  .with(posts_with_comments: Post.where("comments_count > ?", 0))
  .with(posts_with_tags: Post.where("tags_count > ?", 0))

Raises:

  • (ArgumentError) 


486
487
488
489
490
 
# File 'lib/active_record/relation/query_methods.rb', line 486

def with(*args)
  raise ArgumentError, "ActiveRecord::Relation#with does not accept a block" if block_given?
  check_if_method_has_arguments!(__callee__, args)
  spawn.with!(*args)
end

#with!(*args) ⇒ Object

Like #with, but modifies relation in place.



493
494
495
496
497
 
# File 'lib/active_record/relation/query_methods.rb', line 493

def with!(*args) # :nodoc:
  args = process_with_args(args)
  self.with_values |= args
  self
end

#with_recursive(*args) ⇒ Object

Add a recursive Common Table Expression (CTE) that you can then reference within another SELECT statement.

Post.with_recursive(post_and_replies: [Post.where(id: 42), Post.joins('JOIN post_and_replies ON posts.in_reply_to_id = post_and_replies.id')])
# => ActiveRecord::Relation
# WITH post_and_replies AS (
#   (SELECT * FROM posts WHERE id = 42)
#   UNION ALL
#   (SELECT * FROM posts JOIN post_and_replies ON posts.in_reply_to_id = post_and_replies.id)
# )
# SELECT * FROM posts

See #with for more information.



511
512
513
514
 
# File 'lib/active_record/relation/query_methods.rb', line 511

def with_recursive(*args)
  check_if_method_has_arguments!(__callee__, args)
  spawn.with_recursive!(*args)
end

#with_recursive!(*args) ⇒ Object

Like #with_recursive but modifies the relation in place.



517
518
519
520
521
522
 
# File 'lib/active_record/relation/query_methods.rb', line 517

def with_recursive!(*args) # :nodoc:
  args = process_with_args(args)
  self.with_values |= args
  @with_is_recursive = true
  self
end