spectacles

Spectacles

Spectacles adds database view functionality to ActiveRecord. It is heavily inspired by Rails SQL Views (created by https://github.com/aeden but no longer maintained) and built from the ground up to work with Rails.

Spectacles provides the ability to create views in migrations using a similar format to creating tables. It also provides an abstract view class that inherits from ActiveRecord::Base that can be used to create view-backed models.

It currently works with the SQLite, MySQL2, PostgreSQL, and Vertica drivers.

Using Spectacles

Install it

$ gem install spectacles # => OR include it in your Gemfile

Migrations

Create a migration from an query string:

create_view :product_users do
  "SELECT name AS product_name, first_name AS username FROM products JOIN users ON users.id = products.user_id"
end

Create a migration from an ARel object:

create_view :product_users do
  Product.select("products.name AS product_name).select("users.first_name AS username").join(:users)
end

Models

class ProductUser < Spectacles::View # Add relationships
  # Use scopes

  # Your fancy methods
end

Materialized Views

This feature is only supported for PostgreSQL backends.

These are essentially views that cache their result set. In this way they are kind of a cross between tables (which persist data) and views (which are windows onto other tables).

create_materialized_view :product_users do
  <<-SQL.squish
    SELECT name AS product_name, first_name AS username
    FROM products
    JOIN users ON users.id = products.user_id
  SQL
end

class ProductUser < Spectacles::MaterializedView # just like Spectacles::View
end

Because materialized views cache a snapshot of the data as it exists at a point in time (typically when the view was created), you need to manually refresh the view when new data is added to the original tables. You can do this with the #refresh! method on the Spectacles::MaterializedView subclass:

User.create(first_name: "Bob", email: "[e-mail]")
ProductUser.refresh!

Also, you can specify a few different options to create_materialized_view to affect how the new view is created:

• :force - if false (the default), the create will fail if a materialized view with the given name already exists. If true, any materialized view with that name will be dropped before the create runs.

  create_materialized_view :product_users, force: true do
    # ...
  end
  

• :data - if true (the default), the view is immediately populated with the corresponding data. If false, the view will be empty initially, and must be populated by invoking the #refresh! method.

  create_materialized_view :product_users, data: false do
    # ...
  end
  

• :columns - an optional array of names to give the columns in the view. By default, columns in the view will use the names given in the query.

  create_materialized_view :product_users, columns: %i(product_name username) do
    <<-SQL.squish
    SELECT products.name, users.first_name
    FROM products
    JOIN users ON users.id = products.user_id
    SQL
  end
  

• :tablespace - an optional identifier (string or symbol) indicating which namespace the materialized view ought to be created in.

  create_materialized_view :product_users, tablespace: "awesomesauce" do
    # ...
  end
  

• :storage - an optional hash of (database-specific) storage parameters to optimize how the materialized view is stored. (See http://www.postgresql.org/docs/9.4/static/sql-createtable.html#SQL-CREATETABLE-STORAGE-PARAMETERS for details.)

  create_materialized_view :product_users, storage: { fillfactor: 70 } do
    # ...
  end
  

License

Spectacles is licensed under MIT license (Read the LICENSE file for full license)