Run sqldef on Rails.

gem 'sqldef-rails'

Just configure config/database.yml normally.

default: &default
  adapter: postgresql
  username: postgres
  password:
  host: 127.0.0.1

development:
  <<: *default
  database: sqldef_development

test:
  <<: *default
  database: sqldef_test

Dump the current schema to db/schema.sql.

bundle exec rake db:schema:dump

You may use bin/rails instead of bundle exec rake too.

You can show DDLs to be executed to match db/schema.sql.

bundle exec rake db:migrate:status

You can run DDLs to match db/schema.sql.

bundle exec rake db:migrate

The gem is available as open source under the terms of the MIT License.