Class: ActiveRecord::QueryMethods::WhereChain

Relationships & Source Files
Inherits:	Object
Defined in:	activerecord/lib/active_record/relation/query_methods.rb

Overview

WhereChain objects act as placeholder for queries in which #where does not have any parameter. In this case, #where can be chained to return a new relation.

Instance Method Summary

#associated(*associations)

Returns a new relation with joins and where clause to identify associated relations.
#missing(*associations)

Returns a new relation with left outer joins and where clause to identify missing relations.
#not(opts, *rest)

Returns a new relation expressing WHERE + NOT condition according to the conditions in the arguments.

Instance Method Details

#associated(*associations)

Returns a new relation with joins and where clause to identify associated relations.

For example, posts that are associated to a related author:

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

Additionally, multiple relations can be combined. This will return posts associated to both an author and any comments:

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

[ GitHub ]

# File 'activerecord/lib/active_record/relation/query_methods.rb', line 75


def associated(*associations)
  associations.each do |association|
    reflection = scope_association_reflection(association)
    @scope.joins!(association)
    if reflection.options[:class_name]
      self.not(association => { reflection.association_primary_key => nil })
    else
      self.not(reflection.table_name => { reflection.association_primary_key => nil })
    end
  end

  @scope
end

#missing(*associations)

Returns a new relation with left outer joins and where clause to identify missing relations.

For example, posts that are missing a related author:

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

Additionally, multiple relations can be combined. This will return posts that are missing both an author and any comments:

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

[ GitHub ]

# File 'activerecord/lib/active_record/relation/query_methods.rb', line 107


def missing(*associations)
  associations.each do |association|
    reflection = scope_association_reflection(association)
    @scope.left_outer_joins!(association)
    if reflection.options[:class_name]
      @scope.where!(association => { reflection.association_primary_key => nil })
    else
      @scope.where!(reflection.table_name => { reflection.association_primary_key => nil })
    end
  end

  @scope
end

#not(opts, *rest)

Returns a new relation expressing WHERE + NOT condition according to the conditions in the arguments.

#not accepts conditions as a string, array, or hash. See ActiveRecord::QueryMethods#where for more details on each format.

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

User.where.not(["name = ?", "Jon"])
# SELECT * FROM users WHERE NOT (name = 'Jon')

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

User.where.not(name: nil)
# SELECT * FROM users WHERE name IS NOT NULL

User.where.not(name: %w(Ko1 Nobu))
# SELECT * FROM users WHERE name NOT IN ('Ko1', 'Nobu')

User.where.not(name: "Jon", role: "admin")
# SELECT * FROM users WHERE NOT (name = 'Jon' AND role = 'admin')

If there is a non-nil condition on a nullable column in the hash condition, the records that have nil values on the nullable column won’t be returned.

User.create!(nullable_country: nil)
User.where.not(nullable_country: "UK")
# SELECT * FROM users WHERE NOT (nullable_country = 'UK')
# => []

[ GitHub ]

# File 'activerecord/lib/active_record/relation/query_methods.rb', line 49


def not(opts, *rest)
  where_clause = @scope.send(:build_where_clause, opts, rest)

  @scope.where_clause += where_clause.invert

  @scope
end