Module: ActiveRecord::QueryMethods

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

Defined Under Namespace

Classes: 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])

Instance Method Summary collapse

Instance Method Details

#_select!(*fields) ⇒ Object

:nodoc:



388
389
390
391
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 388

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)



1009
1010
1011
1012
1013
1014
1015
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1009

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:



1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1017

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.



1403
1404
1405
1406
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1403

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

#annotate!(*args) ⇒ Object

Like #annotate, but modifies relation in place.



1409
1410
1411
1412
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1409

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

#arel(aliases = nil) ⇒ Object

Returns the Arel object associated with the relation.



1464
1465
1466
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1464

def arel(aliases = nil) # :nodoc:
  @arel ||= build_arel(aliases)
end

#construct_join_dependency(associations, join_type) ⇒ Object

:nodoc:



1468
1469
1470
1471
1472
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1468

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'



1220
1221
1222
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1220

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

#create_with!(value) ⇒ Object

:nodoc:



1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1224

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



1284
1285
1286
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1284

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

#distinct!(value = true) ⇒ Object

Like #distinct, but modifies relation in place.



1289
1290
1291
1292
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1289

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.



250
251
252
253
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 250

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

#eager_load!(*args) ⇒ Object

:nodoc:



255
256
257
258
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 255

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)

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.



1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1445

def excluding(*records)
  records.flatten!(1)
  records.compact!

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

  spawn.excluding!(records)
end

#excluding!(records) ⇒ Object

:nodoc:



1457
1458
1459
1460
1461
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1457

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



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

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

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

:nodoc:



1338
1339
1340
1341
1342
1343
1344
1345
1346
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1338

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)



301
302
303
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 301

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')



1265
1266
1267
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1265

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

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

:nodoc:



1269
1270
1271
1272
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1269

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">]



495
496
497
498
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 495

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

#group!(*args) ⇒ Object

:nodoc:



500
501
502
503
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 500

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')



1071
1072
1073
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1071

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

#having!(opts, *rest) ⇒ Object

:nodoc:



1075
1076
1077
1078
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1075

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

#in_order_of(column, values) ⇒ Object

Allows to specify an order 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



603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 603

def in_order_of(column, values)
  klass.disallow_raw_sql!([column], permit: connection.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.



214
215
216
217
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 214

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

#includes!(*args) ⇒ Object

:nodoc:



219
220
221
222
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 219

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)



975
976
977
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 975

def invert_where
  spawn.invert_where!
end

#invert_where! ⇒ Object

:nodoc:



979
980
981
982
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 979

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



750
751
752
753
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 750

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

#joins!(*args) ⇒ Object

:nodoc:



755
756
757
758
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 755

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"



765
766
767
768
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 765

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

#left_outer_joins!(*args) ⇒ Object

:nodoc:



771
772
773
774
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 771

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'



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

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

#limit!(value) ⇒ Object

:nodoc:



1089
1090
1091
1092
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1089

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.



1112
1113
1114
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1112

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

#lock!(locks = true) ⇒ Object

:nodoc:



1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1116

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



1155
1156
1157
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1155

def none
  spawn.none!
end

#none! ⇒ Object

:nodoc:



1159
1160
1161
1162
1163
1164
1165
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1159

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

#null_relation? ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


1167
1168
1169
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1167

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")



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

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

#offset!(value) ⇒ Object

:nodoc:



1105
1106
1107
1108
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1105

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"



1359
1360
1361
1362
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1359

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

#optimizer_hints!(*args) ⇒ Object

:nodoc:



1364
1365
1366
1367
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1364

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))



1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1041

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:



1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1053

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 = self.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 Postgres, is supported in this way.

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



578
579
580
581
582
583
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 578

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.



586
587
588
589
590
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 586

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 ...



282
283
284
285
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 282

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

#preload!(*args) ⇒ Object

:nodoc:



287
288
289
290
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 287

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



1183
1184
1185
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1183

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

#readonly!(value = true) ⇒ Object

:nodoc:



1187
1188
1189
1190
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1187

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



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

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

#references!(*table_names) ⇒ Object

:nodoc:



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

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.



515
516
517
518
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 515

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.



521
522
523
524
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 521

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’.



634
635
636
637
638
639
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 634

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.



642
643
644
645
646
647
648
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 642

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.



463
464
465
466
467
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 463

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.



470
471
472
473
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 470

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'



1372
1373
1374
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1372

def reverse_order
  spawn.reverse_order!
end

#reverse_order! ⇒ Object

:nodoc:



1376
1377
1378
1379
1380
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1376

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.



937
938
939
940
941
942
943
944
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 937

def rewhere(conditions)
  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



373
374
375
376
377
378
379
380
381
382
383
384
385
386
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 373

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:



1387
1388
1389
1390
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1387

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

#skip_query_cache!(value = true) ⇒ Object

:nodoc:



1382
1383
1384
1385
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1382

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



1198
1199
1200
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1198

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

#strict_loading!(value = true) ⇒ Object

:nodoc:



1202
1203
1204
1205
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1202

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) 


995
996
997
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 995

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

#uniq!(name) ⇒ Object

Deduplicate multiple values.



1415
1416
1417
1418
1419
1420
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1415

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) }



688
689
690
691
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 688

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

#unscope!(*args) ⇒ Object

:nodoc:



693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 693

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_mutability!
      @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)

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.



909
910
911
912
913
914
915
916
917
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 909

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:



919
920
921
922
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 919

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

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))



442
443
444
445
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 442

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

#with!(*args) ⇒ Object

Like #with, but modifies relation in place.



448
449
450
451
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 448

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