Rake task to dump PostgreSQL structure using a compatible pg_dump

pg.rake

namespace :pg do
  namespace :structure do
    # Does exactly the same as db:structure:dump but with one important
    # difference. It tries to use a compatible version of pg_dump. If you see
    # the following error message, use pg:structure:dump instead.
    #
    #   pg_dump: server version: 9.1.0; pg_dump version: 9.0.4
    #   pg_dump: aborting because of server version mismatch
    #   rake aborted!
    #   Error dumping database
    #
    # The pg:structure:dump task overrides the PATH before invoking the regular
    # database structure dump. By default it looks for PostgreSQL 9.1 at
    # /opt/local/lib/postgresql91 where MacPorts places it. But you can override
    # this using POSTGRESQL_PATH on the rake command line.
    desc "Dump the PostgreSQL database structure to an SQL file"
    task :dump => :environment do
      path_to_postgresql = ENV['POSTGRESQL_PATH'] || '/opt/local/lib/postgresql91'
      ENV['PATH'] = File.join(path_to_postgresql, 'bin') + ':' + ENV['PATH']
      Rake::Task['db:structure:dump'].invoke
    end
  end
end