DenormalizeFields

This gem adds a denormalize option to ActiveRecord relation definitions, so that updates on one record are forwarded to its dependent records.

Tested on Rails 7, but should work down to Rails 4.1.

Add, install or require denormalize_fields.

Either:

class User < ApplicationRecord
  has_many :posts, denormalize: { fields: %i[first_name last_name] }
end

Or:

DenormalizeFields.denormalize(
  fields: %i[first_name last_name],
  from:   User,
  onto:   :posts,
)

Resulting behavior:

User.first.posts.pluck(:first_name) # => ['Igor', 'Igor']
User.first.update!(first_name: 'Wanja')
User.first.posts.pluck(:first_name) # => ['Wanja', 'Wanja']

Any validation errors in denormalized fields of dependent records are bubbled up to the source record.

There is also a prefix option:

# assuming there is Rapper#name and Car#owner_name
class Rapper < ApplicationRecord
  has_many :cars, denormalize: { fields: :name, prefix: :owner_ } }
end

Alternatively fields also accepts a Hash to map to other fields on the related record:

# assuming there is Rapper#name and Car#owner
class Rapper < ApplicationRecord
  has_many :cars, denormalize: { fields: { name: :owner } }
end

# multiple fields can be mapped to one, their values will be joined with " "
class Rapper < ApplicationRecord
  has_many :cars, denormalize: { fields: { %i[first_name last_name] => :owner } }
end

Conditional denormalization is also supported:

class Blog < ApplicationRecord
  # don't remove topic from posts when it is removed from blog
  has_many :posts, denormalize: { fields: :topic, if: :topic? }
end

• only works with fields that are in the database, no virtual attributes etc.
• does not work with has_and_belongs_to_many associations
• is based on ActiveRecord callbacks, so does not work for #update_column etc.
• does no denormalization when related records are first created / connected

Bug reports and pull requests are welcome on GitHub at https://github.com/jaynetics/denormalize_fields.

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

Most of these have not been updated in years. Let me know if there is any cool new stuff.

• https://github.com/ursm/activerecord-denormalize
  • similar goal
  • runs custom SQL, so does not work with all DBs
  • skips validations of related records
  • only supports has_many relations, not has_one or belongs_to
• https://github.com/bebanjo/persistize
  • for denormalization onto the same record or owner record only
• https://github.com/ignu/denormalize-field
  • for denormalization onto the same record or owner record only
  • postgres only
• https://github.com/logandk/mongoid_denormalize
  • similar goal
  • mongoid only