Namespace
Methods
A
B
C
D
E
F
G
H
I
J
L
N
O
P
R
S
T
U
V
W
Constants
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])
 
VALID_DIRECTIONS = [:asc, :desc, :ASC, :DESC, "asc", "desc", "ASC", "DESC"].to_set
 
STRUCTURAL_OR_METHODS = Relation::VALUE_METHODS - [:extending, :where, :having, :unscope, :references]
 
DEFAULT_VALUES = { create_with: FROZEN_EMPTY_HASH, where: Relation::WhereClause.empty, having: Relation::WhereClause.empty, from: Relation::FromClause.empty }
 
Instance Public methods
annotate(*args)

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.

    # File activerecord/lib/active_record/relation/query_methods.rb
992 def annotate(*args)
993   check_if_method_has_arguments!(:annotate, args)
994   spawn.annotate!(*args)
995 end
create_with(value)

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'
    # File activerecord/lib/active_record/relation/query_methods.rb
825 def create_with(value)
826   spawn.create_with!(value)
827 end
distinct(value = true)

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
    # File activerecord/lib/active_record/relation/query_methods.rb
872 def distinct(value = true)
873   spawn.distinct!(value)
874 end
eager_load(*args)

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"
    # File activerecord/lib/active_record/relation/query_methods.rb
154 def eager_load(*args)
155   check_if_method_has_arguments!(:eager_load, args)
156   spawn.eager_load!(*args)
157 end
extending(*modules, &block)

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
    # File activerecord/lib/active_record/relation/query_methods.rb
918 def extending(*modules, &block)
919   if modules.any? || block
920     spawn.extending!(*modules, &block)
921   else
922     self
923   end
924 end
extract_associated(association)

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:

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

This is short-hand for:

account.memberships.preload(:user).collect(&:user)
    # File activerecord/lib/active_record/relation/query_methods.rb
187 def extract_associated(association)
188   preload(association).collect(&association)
189 end
from(value, subquery_name = nil)

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
    # File activerecord/lib/active_record/relation/query_methods.rb
853 def from(value, subquery_name = nil)
854   spawn.from!(value, subquery_name)
855 end
group(*args)

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">]
    # File activerecord/lib/active_record/relation/query_methods.rb
315 def group(*args)
316   check_if_method_has_arguments!(:group, args)
317   spawn.group!(*args)
318 end
having(opts, *rest)

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')
    # File activerecord/lib/active_record/relation/query_methods.rb
702 def having(opts, *rest)
703   opts.blank? ? self : spawn.having!(opts, *rest)
704 end
includes(*args)

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' })
    # File activerecord/lib/active_record/relation/query_methods.rb
135 def includes(*args)
136   check_if_method_has_arguments!(:includes, args)
137   spawn.includes!(*args)
138 end
joins(*args)

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
    # File activerecord/lib/active_record/relation/query_methods.rb
483 def joins(*args)
484   check_if_method_has_arguments!(:joins, args)
485   spawn.joins!(*args)
486 end
left_joins(*args)
Alias for: left_outer_joins
left_outer_joins(*args)

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"
Also aliased as: left_joins
    # File activerecord/lib/active_record/relation/query_methods.rb
500 def left_outer_joins(*args)
501   check_if_method_has_arguments!(__callee__, args)
502   spawn.left_outer_joins!(*args)
503 end
limit(value)

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'
    # File activerecord/lib/active_record/relation/query_methods.rb
719 def limit(value)
720   spawn.limit!(value)
721 end
lock(locks = true)

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

    # File activerecord/lib/active_record/relation/query_methods.rb
746 def lock(locks = true)
747   spawn.lock!(locks)
748 end
none()

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
    # File activerecord/lib/active_record/relation/query_methods.rb
789 def none
790   spawn.none!
791 end
offset(value)

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")
    # File activerecord/lib/active_record/relation/query_methods.rb
735 def offset(value)
736   spawn.offset!(value)
737 end
optimizer_hints(*args)

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"
    # File activerecord/lib/active_record/relation/query_methods.rb
947 def optimizer_hints(*args)
948   check_if_method_has_arguments!(:optimizer_hints, args)
949   spawn.optimizer_hints!(*args)
950 end
or(other)

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))
    # File activerecord/lib/active_record/relation/query_methods.rb
676 def or(other)
677   unless other.is_a? Relation
678     raise ArgumentError, "You have passed #{other.class.name} object to #or. Pass an ActiveRecord::Relation object instead."
679   end
680 
681   spawn.or!(other)
682 end
order(*args)

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
    # File activerecord/lib/active_record/relation/query_methods.rb
346 def order(*args)
347   check_if_method_has_arguments!(:order, args)
348   spawn.order!(*args)
349 end
preload(*args)

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)
    # File activerecord/lib/active_record/relation/query_methods.rb
168 def preload(*args)
169   check_if_method_has_arguments!(:preload, args)
170   spawn.preload!(*args)
171 end
readonly(value = true)

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
    # File activerecord/lib/active_record/relation/query_methods.rb
803 def readonly(value = true)
804   spawn.readonly!(value)
805 end
references(*table_names)

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
    # File activerecord/lib/active_record/relation/query_methods.rb
201 def references(*table_names)
202   check_if_method_has_arguments!(:references, table_names)
203   spawn.references!(*table_names)
204 end
reorder(*args)

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'.

    # File activerecord/lib/active_record/relation/query_methods.rb
368 def reorder(*args)
369   check_if_method_has_arguments!(:reorder, args)
370   spawn.reorder!(*args)
371 end
reselect(*args)

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.

    # File activerecord/lib/active_record/relation/query_methods.rb
284 def reselect(*args)
285   check_if_method_has_arguments!(:reselect, args)
286   spawn.reselect!(*args)
287 end
reverse_order()

Reverse the existing order clause on the relation.

User.order('name ASC').reverse_order # generated SQL has 'ORDER BY name DESC'
    # File activerecord/lib/active_record/relation/query_methods.rb
962 def reverse_order
963   spawn.reverse_order!
964 end
rewhere(conditions)

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.

    # File activerecord/lib/active_record/relation/query_methods.rb
662 def rewhere(conditions)
663   unscope(where: conditions.keys).where(conditions)
664 end
select(*fields)

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
    # File activerecord/lib/active_record/relation/query_methods.rb
254 def select(*fields)
255   if block_given?
256     if fields.any?
257       raise ArgumentError, "`select' with block doesn't take arguments."
258     end
259 
260     return super()
261   end
262 
263   raise ArgumentError, "Call `select' with at least one field" if fields.empty?
264   spawn._select!(*fields)
265 end
unscope(*args)

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) }
    # File activerecord/lib/active_record/relation/query_methods.rb
419 def unscope(*args)
420   check_if_method_has_arguments!(:unscope, args)
421   spawn.unscope!(*args)
422 end
where(opts = :chain, *rest)

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.

    # File activerecord/lib/active_record/relation/query_methods.rb
632 def where(opts = :chain, *rest)
633   if :chain == opts
634     WhereChain.new(spawn)
635   elsif opts.blank?
636     self
637   else
638     spawn.where!(opts, *rest)
639   end
640 end
Instance Private methods
arel_column(field)
     # File activerecord/lib/active_record/relation/query_methods.rb
1189 def arel_column(field)
1190   field = klass.attribute_aliases[field] || field
1191   from = from_clause.name || from_clause.value
1192 
1193   if klass.columns_hash.key?(field) && (!from || table_name_matches?(from))
1194     arel_attribute(field)
1195   else
1196     yield field
1197   end
1198 end
arel_columns(columns)
     # File activerecord/lib/active_record/relation/query_methods.rb
1172 def arel_columns(columns)
1173   columns.flat_map do |field|
1174     case field
1175     when Symbol
1176       arel_column(field.to_s) do |attr_name|
1177         connection.quote_table_name(attr_name)
1178       end
1179     when String
1180       arel_column(field, &:itself)
1181     when Proc
1182       field.call
1183     else
1184       field
1185     end
1186   end
1187 end
assert_mutability!()
     # File activerecord/lib/active_record/relation/query_methods.rb
1024 def assert_mutability!
1025   raise ImmutableRelation if @loaded
1026   raise ImmutableRelation if defined?(@arel) && @arel
1027 end
build_arel(aliases)
     # File activerecord/lib/active_record/relation/query_methods.rb
1029 def build_arel(aliases)
1030   arel = Arel::SelectManager.new(table)
1031 
1032   if !joins_values.empty?
1033     build_joins(arel, joins_values.flatten, aliases)
1034   elsif !left_outer_joins_values.empty?
1035     build_left_outer_joins(arel, left_outer_joins_values.flatten, aliases)
1036   end
1037 
1038   arel.where(where_clause.ast) unless where_clause.empty?
1039   arel.having(having_clause.ast) unless having_clause.empty?
1040   if limit_value
1041     limit_attribute = ActiveModel::Attribute.with_cast_value(
1042       "LIMIT",
1043       connection.sanitize_limit(limit_value),
1044       Type.default_value,
1045     )
1046     arel.take(Arel::Nodes::BindParam.new(limit_attribute))
1047   end
1048   if offset_value
1049     offset_attribute = ActiveModel::Attribute.with_cast_value(
1050       "OFFSET",
1051       offset_value.to_i,
1052       Type.default_value,
1053     )
1054     arel.skip(Arel::Nodes::BindParam.new(offset_attribute))
1055   end
1056   arel.group(*arel_columns(group_values.uniq.reject(&:blank?))) unless group_values.empty?
1057 
1058   build_order(arel)
1059 
1060   build_select(arel)
1061 
1062   arel.optimizer_hints(*optimizer_hints_values) unless optimizer_hints_values.empty?
1063   arel.distinct(distinct_value)
1064   arel.from(build_from) unless from_clause.empty?
1065   arel.lock(lock_value) if lock_value
1066   arel.comment(*annotate_values) unless annotate_values.empty?
1067 
1068   arel
1069 end
build_from()
     # File activerecord/lib/active_record/relation/query_methods.rb
1071 def build_from
1072   opts = from_clause.value
1073   name = from_clause.name
1074   case opts
1075   when Relation
1076     if opts.eager_loading?
1077       opts = opts.send(:apply_join_dependency)
1078     end
1079     name ||= "subquery"
1080     opts.arel.as(name.to_s)
1081   else
1082     opts
1083   end
1084 end
build_join_query(manager, buckets, join_type, aliases)
     # File activerecord/lib/active_record/relation/query_methods.rb
1144 def build_join_query(manager, buckets, join_type, aliases)
1145   association_joins = buckets[:association_join]
1146   stashed_joins     = buckets[:stashed_join]
1147   leading_joins     = buckets[:leading_join]
1148   join_nodes        = buckets[:join_node]
1149 
1150   join_sources = manager.join_sources
1151   join_sources.concat(leading_joins) unless leading_joins.empty?
1152 
1153   unless association_joins.empty? && stashed_joins.empty?
1154     alias_tracker = alias_tracker(leading_joins + join_nodes, aliases)
1155     join_dependency = construct_join_dependency(association_joins, join_type)
1156     join_sources.concat(join_dependency.join_constraints(stashed_joins, alias_tracker))
1157   end
1158 
1159   join_sources.concat(join_nodes) unless join_nodes.empty?
1160 end
build_joins(manager, joins, aliases)
     # File activerecord/lib/active_record/relation/query_methods.rb
1103 def build_joins(manager, joins, aliases)
1104   buckets = Hash.new { |h, k| h[k] = [] }
1105 
1106   unless left_outer_joins_values.empty?
1107     left_joins = valid_association_list(left_outer_joins_values.flatten)
1108     buckets[:stashed_join] << construct_join_dependency(left_joins, Arel::Nodes::OuterJoin)
1109   end
1110 
1111   joins.map! do |join|
1112     if join.is_a?(String)
1113       table.create_string_join(Arel.sql(join.strip)) unless join.blank?
1114     else
1115       join
1116     end
1117   end.delete_if(&:blank?).uniq!
1118 
1119   while joins.first.is_a?(Arel::Nodes::Join)
1120     join_node = joins.shift
1121     if join_node.is_a?(Arel::Nodes::StringJoin) && !buckets[:stashed_join].empty?
1122       buckets[:join_node] << join_node
1123     else
1124       buckets[:leading_join] << join_node
1125     end
1126   end
1127 
1128   joins.each do |join|
1129     case join
1130     when Hash, Symbol, Array
1131       buckets[:association_join] << join
1132     when ActiveRecord::Associations::JoinDependency
1133       buckets[:stashed_join] << join
1134     when Arel::Nodes::Join
1135       buckets[:join_node] << join
1136     else
1137       raise "unknown class: %s" % join.class.name
1138     end
1139   end
1140 
1141   build_join_query(manager, buckets, Arel::Nodes::InnerJoin, aliases)
1142 end
build_left_outer_joins(manager, outer_joins, aliases)
     # File activerecord/lib/active_record/relation/query_methods.rb
1097 def build_left_outer_joins(manager, outer_joins, aliases)
1098   buckets = Hash.new { |h, k| h[k] = [] }
1099   buckets[:association_join] = valid_association_list(outer_joins)
1100   build_join_query(manager, buckets, Arel::Nodes::OuterJoin, aliases)
1101 end
build_order(arel)
     # File activerecord/lib/active_record/relation/query_methods.rb
1242 def build_order(arel)
1243   orders = order_values.uniq
1244   orders.reject!(&:blank?)
1245 
1246   arel.order(*orders) unless orders.empty?
1247 end
build_select(arel)
     # File activerecord/lib/active_record/relation/query_methods.rb
1162 def build_select(arel)
1163   if select_values.any?
1164     arel.project(*arel_columns(select_values.uniq))
1165   elsif klass.ignored_columns.any?
1166     arel.project(*klass.column_names.map { |field| arel_attribute(field) })
1167   else
1168     arel.project(table[Arel.star])
1169   end
1170 end
check_if_method_has_arguments!(method_name, args)

Checks to make sure that the arguments are not blank. Note that if some blank-like object were initially passed into the query method, then this method will not raise an error.

Example:

Post.references()   # raises an error
Post.references([]) # does not raise an error

This particular method should be called with a method_name and the args passed into that method as an input. For example:

def references(*args)

check_if_method_has_arguments!("references", args)
...

end

     # File activerecord/lib/active_record/relation/query_methods.rb
1328 def check_if_method_has_arguments!(method_name, args)
1329   if args.blank?
1330     raise ArgumentError, "The method .#{method_name}() must contain arguments."
1331   end
1332 end
does_not_support_reverse?(order)
     # File activerecord/lib/active_record/relation/query_methods.rb
1231 def does_not_support_reverse?(order)
1232   # Account for String subclasses like Arel::Nodes::SqlLiteral that
1233   # override methods like #count.
1234   order = String.new(order) unless order.instance_of?(String)
1235 
1236   # Uses SQL function with multiple arguments.
1237   (order.include?(",") && order.split(",").find { |section| section.count("(") != section.count(")") }) ||
1238     # Uses "nulls first" like construction.
1239     /\bnulls\s+(?:first|last)\b/i.match?(order)
1240 end
having_clause_factory()
order_column(field)
     # File activerecord/lib/active_record/relation/query_methods.rb
1302 def order_column(field)
1303   arel_column(field) do |attr_name|
1304     if attr_name == "count" && !group_values.empty?
1305       arel_attribute(attr_name)
1306     else
1307       Arel.sql(connection.quote_table_name(attr_name))
1308     end
1309   end
1310 end
preprocess_order_args(order_args)
     # File activerecord/lib/active_record/relation/query_methods.rb
1264 def preprocess_order_args(order_args)
1265   order_args.reject!(&:blank?)
1266   order_args.map! do |arg|
1267     klass.sanitize_sql_for_order(arg)
1268   end
1269   order_args.flatten!
1270 
1271   @klass.disallow_raw_sql!(
1272     order_args.flat_map { |a| a.is_a?(Hash) ? a.keys : a },
1273     permit: connection.column_name_with_order_matcher
1274   )
1275 
1276   validate_order_args(order_args)
1277 
1278   references = order_args.grep(String)
1279   references.map! { |arg| arg =~ /^\W?(\w+)\W?\./ && $1 }.compact!
1280   references!(references) if references.any?
1281 
1282   # if a symbol is given we prepend the quoted table name
1283   order_args.map! do |arg|
1284     case arg
1285     when Symbol
1286       order_column(arg.to_s).asc
1287     when Hash
1288       arg.map { |field, dir|
1289         case field
1290         when Arel::Nodes::SqlLiteral
1291           field.send(dir.downcase)
1292         else
1293           order_column(field.to_s).send(dir.downcase)
1294         end
1295       }
1296     else
1297       arg
1298     end
1299   end.flatten!
1300 end
reverse_sql_order(order_query)
     # File activerecord/lib/active_record/relation/query_methods.rb
1204 def reverse_sql_order(order_query)
1205   if order_query.empty?
1206     return [arel_attribute(primary_key).desc] if primary_key
1207     raise IrreversibleOrderError,
1208       "Relation has no current order and table has no primary key to be used as default order"
1209   end
1210 
1211   order_query.flat_map do |o|
1212     case o
1213     when Arel::Attribute
1214       o.desc
1215     when Arel::Nodes::Ordering
1216       o.reverse
1217     when String
1218       if does_not_support_reverse?(o)
1219         raise IrreversibleOrderError, "Order #{o.inspect} cannot be reversed automatically"
1220       end
1221       o.split(",").map! do |s|
1222         s.strip!
1223         s.gsub!(/\sasc\Z/i, " DESC") || s.gsub!(/\sdesc\Z/i, " ASC") || (s << " DESC")
1224       end
1225     else
1226       o
1227     end
1228   end
1229 end
structurally_incompatible_values_for_or(other)
     # File activerecord/lib/active_record/relation/query_methods.rb
1335 def structurally_incompatible_values_for_or(other)
1336   values = other.values
1337   STRUCTURAL_OR_METHODS.reject do |method|
1338     default = DEFAULT_VALUES[method]
1339     @values.fetch(method, default) == values.fetch(method, default)
1340   end
1341 end
table_name_matches?(from)
     # File activerecord/lib/active_record/relation/query_methods.rb
1200 def table_name_matches?(from)
1201   /(?:\A|(?<!FROM)\s)(?:\b#{table.name}\b|#{connection.quote_table_name(table.name)})(?!\.)/i.match?(from.to_s)
1202 end
valid_association_list(associations)
     # File activerecord/lib/active_record/relation/query_methods.rb
1086 def valid_association_list(associations)
1087   associations.each do |association|
1088     case association
1089     when Hash, Symbol, Array
1090       # valid
1091     else
1092       raise ArgumentError, "only Hash, Symbol and Array are allowed"
1093     end
1094   end
1095 end
validate_order_args(args)
     # File activerecord/lib/active_record/relation/query_methods.rb
1252 def validate_order_args(args)
1253   args.each do |arg|
1254     next unless arg.is_a?(Hash)
1255     arg.each do |_key, value|
1256       unless VALID_DIRECTIONS.include?(value)
1257         raise ArgumentError,
1258           "Direction \"#{value}\" is invalid. Valid directions are: #{VALID_DIRECTIONS.to_a.inspect}"
1259       end
1260     end
1261   end
1262 end
where_clause_factory()
Also aliased as: having_clause_factory
     # File activerecord/lib/active_record/relation/query_methods.rb
1343 def where_clause_factory
1344   @where_clause_factory ||= Relation::WhereClauseFactory.new(klass, predicate_builder)
1345 end