Rails: kill all PostgreSQL connections.

db.rake

namespace :db do
  desc "Kick out PostgreSQL users from the database."
  task kick: [:environment] do
    begin
      ActiveRecord::Base.connection.execute <<-SQL
      SELECT pg_terminate_backend(pg_stat_activity.pid)
      FROM pg_stat_activity
      WHERE pg_stat_activity.datname = '#{ActiveRecord::Base.connection.current_database}';
    SQL
    rescue ActiveRecord::StatementInvalid
      puts "All connections killed."
    end
  end
end