IgnorableColumns¶ ↑

Motivation is to allow ignoring certain columns both at model level (columns/attributes) as well as database queries level. It works with includes and eager_load as well as simple queries.

Tested on Rails4, should work on Rails3. Not tested on Rails5.

Example Usage¶ ↑

class Topic < ActiveRecord::Base
  ignore_columns :name, :body, :timezone
  ignore_columns_in_sql # optional, recommended for better performance
  ignore_columns_preload_all_subclass # optional, used for preloading subclasses so that constantizing can work
end

ignore_columns

• This makes the model ignore the attributes stated by default and exposes methods to include them back whenever we want them.

• ignore_columns must be defined before using ignore_columns_in_sql.

ignore_columns_in_sql

• This makes the model run optimised sql that only returns those non ignored columns.

ignore_columns_preload_all_subclass

• This makes the model preload all the different subclasses that is generated by ignore_columns.

• i.e: if Topic has ignore_columns :name, :body. This preloads the following subclasses: TopicWithName, TopicWithBody, TopicWithNameBody

• ignore_columns_preload_all_subclass must be defined after everything in your model that affects the default_scope.

To temporarily use the ignored columns:

Topic.including_ignored_columns.where(name: 'Data Rocks')
Topic.including_ignored_columns(:name).where(name: 'Data Rocks')

For use with relations see below example:

Has many¶ ↑

class Topic < ActiveRecord::Base
  ignore_columns :name, :body, :timezone
  ignore_columns_in_sql # optional, recommended for better performance
  ignore_columns_preload_all_subclass # optional, used for preloading subclasses so that constantizing can work

  belongs_to :author
  belongs_to :author_with_location, class_name: Author.including_ignored_columns(:location).name, foreign_key: 'topic_id'
end

class Author < ActiveRecord::Base
  ignore_columns :location, :updated_at
  ignore_columns_in_sql # optional, recommended for better performance
  ignore_columns_preload_all_subclass # optional, used for preloading subclasses so that constantizing can work

  has_many :topics
  has_many :topics_with_body, class_name: Topic.including_ignored_columns(:body).name
  has_many :topics_with_all, class_name: Topic.including_ignored_columns.name
end

Author.last.topics_with_body
Topic.where(name: 'MyTopic').author_with_location
Author.includes(:topics_with_all).last.topics_with_all
Author.eager_load(:topics_with_all).last.topics_with_all

Self Referential¶ ↑

class Topic < ActiveRecord::Base
  ignore_columns :name, :body, :timezone
  ignore_columns_in_sql # optional, recommended for better performance
  ignore_columns_preload_all_subclass # optional, used for preloading subclasses so that constantizing can work

  belongs_to :parent_topic, class_name: Topic.name
  has_many :child_topics, class_name: Topic.name, foreign_key: 'parent_id'

  belongs_to :parent_topic_with_all, class_name: Topic.including_ignored_columns.name
  has_many :child_topics_with_all, class_name: Topic.including_ignored_columns.name, foreign_key: 'parent_id'
end

Topic.where(name: 'MyTopic').child_topics_with_all

Many to many¶ ↑

class Topic < ActiveRecord::Base
  ignore_columns :name, :body, :timezone
  ignore_columns_in_sql # optional, recommended for better performance
  ignore_columns_preload_all_subclass # optional, used for preloading subclasses so that constantizing can work

  has_many :author_topics
  has_many :authors, through: :author_topics
end

class Author < ActiveRecord::Base
  ignore_columns :location, :updated_at
  ignore_columns_in_sql # optional, recommended for better performance
  ignore_columns_preload_all_subclass # optional, used for preloading subclasses so that constantizing can work

  has_many :author_topics
  has_many :topics, through: :author_topics
end

class AuthorTopic < ActiveRecord::Base
  belongs_to :author
  belongs_to :topic

  belongs_to :authors_with_location, class_name: Author.including_ignored_columns(:location).name, foreign_key: 'author_id'
end

Topic.where(name: 'MyTopic').last.authors_with_location

Limitations¶ ↑

• does not support has and belongs to many relations

• does not support polymorphic relations

• because of the ActiveRecord implementation when using count it should be used as count(:all)

(else a middleware could be implemented but it is out of the scope of this gem)

TO DO¶ ↑

1. specs for relations other than has many

2. specs for concurrency

3. support for rails 5

4. examples (and / or another gem) for use with graphql

Inspired by github.com/nthj/ignorable