scenic-cascade

scenic-cascade

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

Installation

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

Usage

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

How it works

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.

[!WARNING] Currently, index re-creation is not supported. Please change a migration file to recreate indexes if it contains drop_view for materialized views.

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

Development

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.

Contributing

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.

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.