Records timestamps on insert/update helper for PostgreSQL

pg_record_timestamps.sql

CREATE OR REPLACE FUNCTION add_timestamps_to_table(_table text, _type text) RETURNS void AS $$
BEGIN
  EXECUTE format('ALTER TABLE %I ADD COLUMN IF NOT EXISTS created_at %s', _table, _type);
  EXECUTE format('ALTER TABLE %I ADD COLUMN IF NOT EXISTS updated_at %s', _table, _type);
END;
$$ LANGUAGE 'plpgsql';

CREATE OR REPLACE FUNCTION set_timestamps_not_null_on_table(_table text) RETURNS void AS $$
BEGIN
  EXECUTE format('ALTER TABLE %I ALTER COLUMN created_at SET NOT NULL', _table);
  EXECUTE format('ALTER TABLE %I ALTER COLUMN updated_at SET NOT NULL', _table);
END;
$$ LANGUAGE 'plpgsql';

-------------
-- TRIGGER --
-------------
CREATE OR REPLACE FUNCTION record_creation_time() RETURNS TRIGGER AS $$
DECLARE force boolean;
BEGIN
  force = false;
  if TG_NARGS > 0 then
    force = TG_ARGV[0];
  end if;

  if NEW.created_at is null or force is true then
    NEW.created_at = NOW();
  end if;
  if NEW.updated_at is null or force is true then
    NEW.updated_at = NOW();
  end if;
  return NEW;
END;
$$ LANGUAGE 'plpgsql';

CREATE OR REPLACE FUNCTION record_update_time() RETURNS TRIGGER AS $$
DECLARE force boolean;
BEGIN
  force = false;
  if TG_NARGS > 0 then
    force = TG_ARGV[0];
  end if;

  if NEW.updated_at is null or force is true then
    NEW.updated_at = NOW();
  end if;
  return NEW;
END;
$$ LANGUAGE 'plpgsql';

--------------------
-- CREATE TRIGGER --
--------------------
CREATE OR REPLACE FUNCTION record_timestamps_on_update(_table text, _force boolean = false) RETURNS void AS $$
BEGIN
  EXECUTE format('DROP TRIGGER IF EXISTS update_updated_at ON %I', _table);
  EXECUTE format(
    'CREATE TRIGGER record_update_time BEFORE UPDATE ON %I FOR EACH ROW EXECUTE PROCEDURE record_update_time(%L)',
    _table, _force
  );
END;
$$ LANGUAGE 'plpgsql';

CREATE OR REPLACE FUNCTION record_timestamps_on_create(_table text, _force boolean = false) RETURNS void AS $$
BEGIN
  EXECUTE format('DROP TRIGGER IF EXISTS record_creation_time ON %I', _table);
  EXECUTE format(
    'CREATE TRIGGER record_creation_time BEFORE INSERT ON %I FOR EACH ROW EXECUTE PROCEDURE record_creation_time(%L)',
    _table, _force
  );
END;
$$ LANGUAGE 'plpgsql';

CREATE OR REPLACE FUNCTION record_timestamps_for_table(_table text, _force boolean = false) RETURNS void AS $$
BEGIN
  PERFORM record_timestamps_on_update(_table, _force);
  PERFORM record_timestamps_on_create(_table, _force);
END;
$$ LANGUAGE 'plpgsql';