scenic-cascade is a scenic migration file generator that supports cascading view updates.

Add this line to your application's Gemfile:

gem 'scenic-cascade'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install scenic-cascade

To generate migration files, use scenic:view:cascade generator instead of scenic:view. The following example generates migration files for search_results view.

$ bin/rails generate scenic:view:cascade search_results
      create db/views/search_results_v01.sql
      create db/migrate/20220714233704_create_search_results.rb

Consider a situation where the following three views exist:

• first_results is a parent view (version 1)
• second_results is a materialized view that depends on first_results (version 3)
• third_results is a view that depends on first_results and second_results (version 2)

-- first_results
SELECT 'foo' AS bar;

-- second_results
SELECT * FROM first_results;

-- third_results
SELECT * FROM first_results UNION SELECT * FROM second_results;

Executing the scenic:view:cascade generator for first_results in this state will generate the following migration file:

$ bin/rails generate scenic:view:cascade first_results
      create db/views/first_results_v02.sql
      create db/migrate/20220714233704_update_first_results_to_version_2.rb

Since all dependencies are described, you can execute bin/rails db:migrate without changing the migration file.

class UpdateSearchResultsToVersion2 < ActiveRecord::Migration
  def change
    drop_view :third_results, revert_to_version: 2, materialized: false
    drop_view :second_results, revert_to_version: 3, materialized: true
    replace_view :first_results, version: 2, revert_to_version: 1
    create_view :second_results, version: 3, materialized: true
    create_view :third_results, version: 2, materialized: false
  end
end

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec 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.

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

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