The project is in a healthy, maintained state
An extension for Active Record for querying records with or without associated records
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 Project Readme

RecordsWithRecords

Please consider that this gem is currently in a beta state

This gem aims to simplify exists queries

Installation

Add this line to your application's Gemfile:

gem 'records_with_records'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install records_with_records

Usage

Assume you have a relation like this

class User < ActiveRecord::Base
  has_many :received_messages, class_name: 'Message', foreign_key: :receiver_id
end

Exists

To get all Users with associated Messages you would write

User.where(Message.where('receiver_id = users.id').arel.exists)
=> SELECT "users".* FROM "users" WHERE EXISTS (SELECT "messages".* FROM "messages" WHERE (receiver_id = users.id))

Instead you can now write

User.where_exists(:received_messages)
=> SELECT "users".* FROM "users" WHERE EXISTS (SELECT "messages".* FROM "messages" WHERE ("messages"."receiver_id" = "users"."id"))

Not exists

Querying records without associated records is also possible

User.where_not_exists(:received_messages)
=> SELECT "users".* FROM "users" WHERE NOT (EXISTS (SELECT "messages".* FROM "messages" WHERE ("messages"."receiver_id" = "users"."id")))

Additional scope

You can pass a scope as second argument

User.where_not_exists(:received_messages, -> { where(received_at: 5.hours.ago..) })
=> SELECT "users".* FROM "users" WHERE NOT (EXISTS (SELECT "messages".* FROM "messages" WHERE "messages"."received_at" >= $1 AND ("messages"."receiver_id" = "users"."id"))) [["received_at", "2021-05-01 04:16:42.325804"]]

Association scope

Scopes defined on the association are also applied

class User < ActiveRecord::Base
  has_many :pending_messages, -> { where(messages: {received_at: nil}) }, class_name: 'Message', foreign_key: :receiver_id
end

User.where_exists(:pending_messages)
=> SELECT "users".* FROM "users" WHERE EXISTS (SELECT "messages".* FROM "messages" WHERE "messages"."received_at" IS NULL AND ("messages"."receiver_id" = "users"."id"))

Caveats

Querying on the existence of belongs_to associations is currently not possible.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/records_with_records. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the RecordsWithRecords project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.