Module: ActiveRecord::QueryMethods

Extended by:
ActiveSupport::Concern
Includes:
ActiveModel::ForbiddenAttributesProtection
Included in:
Relation
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, :from, :readonly, :having, :optimizer_hints])

Instance Method Summary collapse

Methods included from ActiveSupport::Concern

append_features, class_methods, extended, included

Instance Method Details

#_select!(*fields) ⇒ Object

:nodoc:



281
282
283
284
285
286
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 281

def _select!(*fields) # :nodoc:
  fields.compact_blank!
  fields.flatten!
  self.select_values += fields
  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.



1006
1007
1008
1009
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1006

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

#annotate!(*args) ⇒ Object

Like #annotate, but modifies relation in place.



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

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

#arel(aliases = nil) ⇒ Object

Returns the Arel object associated with the relation.



1018
1019
1020
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1018

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

#construct_join_dependency(associations, join_type) ⇒ Object

:nodoc:



1022
1023
1024
1025
1026
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1022

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'



839
840
841
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 839

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

#create_with!(value) ⇒ Object

:nodoc:



843
844
845
846
847
848
849
850
851
852
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 843

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



886
887
888
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 886

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

#distinct!(value = true) ⇒ Object

Like #distinct, but modifies relation in place.



891
892
893
894
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 891

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

#eager_load(*args) ⇒ Object

Forces eager loading by performing a LEFT OUTER JOIN on args:

User.eager_load(:posts)
# SELECT "users"."id" AS t0_r0, "users"."name" AS t0_r1, ...
# FROM "users" LEFT OUTER JOIN "posts" ON "posts"."user_id" =
# "users"."id"



168
169
170
171
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 168

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

#eager_load!(*args) ⇒ Object

:nodoc:



173
174
175
176
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 173

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



932
933
934
935
936
937
938
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 932

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

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

:nodoc:



940
941
942
943
944
945
946
947
948
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 940

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)



201
202
203
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 201

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

#from(value, subquery_name = nil) ⇒ Object

Specifies 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

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



867
868
869
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 867

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

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

:nodoc:



871
872
873
874
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 871

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">]



329
330
331
332
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 329

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

#group!(*args) ⇒ Object

:nodoc:



334
335
336
337
338
339
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 334

def group!(*args) # :nodoc:
  args.flatten!

  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')



716
717
718
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 716

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

#having!(opts, *rest) ⇒ Object

:nodoc:



720
721
722
723
724
725
726
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 720

def having!(opts, *rest) # :nodoc:
  opts = sanitize_forbidden_attributes(opts)
  references!(PredicateBuilder.references(opts)) if Hash === opts

  self.having_clause += having_clause_factory.build(opts, rest)
  self
end

#includes(*args) ⇒ Object

Specify relationships to be included in the result set. For example:

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

allows you to access the address attribute of the User model without firing an additional query. This will often result in a performance improvement over a simple join.

You can also specify multiple relationships, like this:

users = User.includes(:address, :friends)

Loading nested relationships is possible using a Hash:

users = 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')

Will throw an error, but this will work:

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

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

If you pass the conditions via 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' })



149
150
151
152
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 149

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

#includes!(*args) ⇒ Object

:nodoc:



154
155
156
157
158
159
160
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 154

def includes!(*args) # :nodoc:
  args.compact_blank!
  args.flatten!

  self.includes_values |= args
  self
end

#joins(*args) ⇒ Object

Performs a 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" "comments_posts"
#   ON "comments_posts"."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



497
498
499
500
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 497

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

#joins!(*args) ⇒ Object

:nodoc:



502
503
504
505
506
507
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 502

def joins!(*args) # :nodoc:
  args.compact!
  args.flatten!
  self.joins_values += args
  self
end

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

Performs a left outer joins on args:

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



514
515
516
517
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 514

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

#left_outer_joins!(*args) ⇒ Object

:nodoc:



520
521
522
523
524
525
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 520

def left_outer_joins!(*args) # :nodoc:
  args.compact!
  args.flatten!
  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'



733
734
735
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 733

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

#limit!(value) ⇒ Object

:nodoc:



737
738
739
740
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 737

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.



760
761
762
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 760

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

#lock!(locks = true) ⇒ Object

:nodoc:



764
765
766
767
768
769
770
771
772
773
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 764

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



803
804
805
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 803

def none
  spawn.none!
end

#none! ⇒ Object

:nodoc:



807
808
809
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 807

def none! # :nodoc:
  where!("1=0").extending!(NullRelation)
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")



749
750
751
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 749

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

#offset!(value) ⇒ Object

:nodoc:



753
754
755
756
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 753

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"



961
962
963
964
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 961

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

#optimizer_hints!(*args) ⇒ Object

:nodoc:



966
967
968
969
970
971
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 966

def optimizer_hints!(*args) # :nodoc:
  args.flatten!

  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). Neither relation may have a #limit, #offset, or #distinct set.

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



690
691
692
693
694
695
696
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 690

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

  spawn.or!(other)
end

#or!(other) ⇒ Object

:nodoc:



698
699
700
701
702
703
704
705
706
707
708
709
710
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 698

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

Allows to specify an order attribute:

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

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

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

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



360
361
362
363
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 360

def order(*args)
  check_if_method_has_arguments!(:order, args)
  spawn.order!(*args)
end

#order!(*args) ⇒ Object

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



366
367
368
369
370
371
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 366

def order!(*args) # :nodoc:
  preprocess_order_args(args)

  self.order_values += args
  self
end

#preload(*args) ⇒ Object

Allows preloading of args, in the same way that #includes does:

User.preload(:posts)
# SELECT "posts".* FROM "posts" WHERE "posts"."user_id" IN (1, 2, 3)



182
183
184
185
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 182

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

#preload!(*args) ⇒ Object

:nodoc:



187
188
189
190
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 187

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

#readonly(value = true) ⇒ Object

Sets readonly attributes for the returned relation. If value is true (default), attempting to update a record will result in an error.

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



817
818
819
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 817

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

#readonly!(value = true) ⇒ Object

:nodoc:



821
822
823
824
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 821

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



215
216
217
218
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 215

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

#references!(*table_names) ⇒ Object

:nodoc:



220
221
222
223
224
225
226
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 220

def references!(*table_names) # :nodoc:
  table_names.flatten!
  table_names.map!(&:to_s)

  self.references_values |= table_names
  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’.



382
383
384
385
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 382

def reorder(*args)
  check_if_method_has_arguments!(:reorder, args)
  spawn.reorder!(*args)
end

#reorder!(*args) ⇒ Object

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



388
389
390
391
392
393
394
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 388

def reorder!(*args) # :nodoc:
  preprocess_order_args(args) unless args.all?(&:blank?)

  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.



298
299
300
301
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 298

def reselect(*args)
  check_if_method_has_arguments!(:reselect, args)
  spawn.reselect!(*args)
end

#reselect!(*args) ⇒ Object

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



304
305
306
307
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 304

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'



976
977
978
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 976

def reverse_order
  spawn.reverse_order!
end

#reverse_order! ⇒ Object

:nodoc:



980
981
982
983
984
985
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 980

def reverse_order! # :nodoc:
  orders = order_values.uniq
  orders.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.



676
677
678
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 676

def rewhere(conditions)
  unscope(where: conditions.keys).where(conditions)
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">]

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: "value", other_field: "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

Raises:

  • (ArgumentError) 


268
269
270
271
272
273
274
275
276
277
278
279
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 268

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

    return super()
  end

  raise ArgumentError, "Call `select' with at least one field" if fields.empty?
  spawn._select!(*fields)
end

#skip_preloading! ⇒ Object

:nodoc:



992
993
994
995
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 992

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

#skip_query_cache!(value = true) ⇒ Object

:nodoc:



987
988
989
990
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 987

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



433
434
435
436
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 433

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

#unscope!(*args) ⇒ Object

:nodoc:



438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 438

def unscope!(*args) # :nodoc:
  args.flatten!
  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 = Array(target_value).map(&:to_s)
        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(opts = :chain, *rest) ⇒ 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 #not to return a new relation that negates the where clause.

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

See WhereChain for more details on #not.

blank condition

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



646
647
648
649
650
651
652
653
654
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 646

def where(opts = :chain, *rest)
  if :chain == opts
    WhereChain.new(spawn)
  elsif opts.blank?
    self
  else
    spawn.where!(opts, *rest)
  end
end

#where!(opts, *rest) ⇒ Object

:nodoc:



656
657
658
659
660
661
 
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 656

def where!(opts, *rest) # :nodoc:
  opts = sanitize_forbidden_attributes(opts)
  references!(PredicateBuilder.references(opts)) if Hash === opts
  self.where_clause += where_clause_factory.build(opts, rest)
  self
end