F(x) adds methods to ActiveRecord::Migration to create and manage database functions and triggers in Rails.

Using F(x), you can bring the power of SQL functions and triggers to your Rails application without having to switch your schema format to SQL. F(x) provides a convention for versioning functions and triggers that keeps your migration history consistent and reversible and avoids having to duplicate SQL strings across migrations. As an added bonus, you define the structure of your function in a SQL file, meaning you get full SQL syntax highlighting in the editor of your choice and can easily test your SQL in the database console during development.

F(x) ships with support for PostgreSQL. The adapter is configurable (see Fx::Configuration) and has a minimal interface (see Fx::Adapters::Postgres) that other gems can provide.

You've got this great idea for a trigger you'd like to call uppercase_users_name. You can create the migration and the corresponding definition file with the following command:

% rails generate fx:trigger uppercase_users_name
      create  db/triggers/uppercase_users_name_v01.sql
      create  db/migrate/[TIMESTAMP]_create_trigger_uppercase_users_name.rb

Edit the db/triggers/uppercase_users_name_v01.sql file with the SQL statement that defines your trigger. In our example, this might look something like this:

CREATE TRIGGER uppercase_users_name
    BEFORE INSERT ON users
    FOR EACH ROW
    EXECUTE PROCEDURE uppercase_users_name();

As you see, we execute a function called uppercase_users_name before each INSERT on the users table, which is a function we don't have yet.

% rails generate fx:function uppercase_users_name
      create  db/functions/uppercase_users_name_v01.sql
      create  db/migrate/[TIMESTAMP]_create_function_uppercase_users_name.rb

The generated migrations contains create_function and create_trigger statements. The migration is reversible and the schema will be dumped into your schema.rb file.

% rake db:migrate

Here's where F(x) really shines. Run that same function generator once more:

% rails generate fx:function uppercase_users_name
      create  db/functions/uppercase_users_name_v02.sql
      create  db/migrate/[TIMESTAMP]_update_function_uppercase_users_name_to_version_2.rb

F(x) detected that we already had an existing uppercase_users_name function at version 1, created a copy of that definition as version 2, and created a migration to update to the version 2 schema. All that's left for you to do is tweak the schema in the new definition and run the update_function migration.

Scenic gives you drop_trigger and drop_function too:

def change
  drop_function :uppercase_users_name, revert_to_version: 2
end

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