Example of using Postgres advisory locks with Rails ActiveRecord

credential.rb

class Credential < ApplicationRecord
  CredentialNotAvailableError = Class.new(StandardError)

  def self.find_and_lock_credential
    where("pg_try_advisory_lock(to_regclass('#{table_name}')::int, id::int)").first
  end

  def self.find_and_lock_credential!
    find_and_lock_credential || raise(CredentialNotAvailableError)
  end

  def self.all_locks
    connection.execute("SELECT * FROM pg_locks WHERE locktype = 'advisory' AND classid = to_regclass('#{table_name}')::int")
  end

  def locked?
    self.class.connection.execute("SELECT 1 as one FROM pg_locks WHERE locktype = 'advisory' AND classid = to_regclass('#{self.class.table_name}')::int AND objid = #{id}").ntuples > 0
  end

  def unlock
    self.class.connection.execute("SELECT pg_advisory_unlock(to_regclass('#{self.class.table_name}')::int, #{id}::int)").first["pg_advisory_unlock"]
  end

  def unlock!
    unlock while locked?
  end
end