A Rake task for destructively copying one environment's database to another, preserving IDs. Should support different database adapters, but aborts if the schema versions don't match. Not recommended for large tables.

clone.rake

namespace :clone do
  desc 'destructively copy the source environment database to the target'
  task :database, [:source, :target] => :environment do |t, args|
    source = args[:source].to_sym
    target = args[:target].to_sym

    versions = {}

    [ source, target ].each do |db|
      ActiveRecord::Base.establish_connection db
      versions[db] = ActiveRecord::Migrator.current_version
    end

    if versions[source] != versions[target]
      abort "Schema mismatch! #{source}: #{versions[source]}, #{target}: #{versions[target]}"
    end

    tables = ActiveRecord::Base.connection.tables - %w(schema_migrations)
    tables.sort.each do |table|
      ActiveRecord::Base.connection.execute "delete from #{table}"
      print table
      ActiveRecord::Base.establish_connection source
      fixtures = ActiveRecord::Base.connection.select_all("select * from #{table}")
      ActiveRecord::Base.establish_connection target
      fixtures.each do |fixture|
        print '.'
        ActiveRecord::Base.connection.insert_fixture fixture, table
      end
      puts
    end
  end
end