instance method `missing`

Ruby on Rails 8.1.2

Since v6.1.7.10

Available in: v6.1.7.10 v7.0.10 v7.1.6 v7.2.3 v8.0.4 v8.1.2

Compare with:

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

Parameters

associations rest

Source

# File activerecord/lib/active_record/relation/query_methods.rb, line 124
      def missing(*associations)
        associations.each do |association|
          reflection = scope_association_reflection(association)
          @scope.left_outer_joins!(association)
          association_conditions = Array(reflection.association_primary_key).index_with(nil)
          if reflection.options[:class_name]
            @scope.where!(association => association_conditions)
          else
            @scope.where!(reflection.table_name => association_conditions)
          end
        end

        @scope
      end

Defined in activerecord/lib/active_record/relation/query_methods.rb line 124 · View on GitHub · Improve this page · Find usages on GitHub

Defined in ActiveRecord::QueryMethods::WhereChain

Signature

Parameters