Email domain type for postgres

email.sql

CREATE EXTENSION IF NOT EXISTS citext;

-- http://www.rfc-editor.org/errata_search.php?rfc=3696&eid=1690 
CREATE DOMAIN email AS citext
CHECK (
  VALUE IS NULL OR (
    -- is not more than 254 chars
    length(VALUE) <= 254 AND

    -- vaguely looks like an email address
    VALUE ~ '.@.' AND

    -- local part is not more than 64 chars
    length(split_part(VALUE, '@', 1)) <= 64 AND

    -- domain part is not more than 255 chars
    length(split_part(VALUE, '@', 2)) <= 255
  )
);

Field type allows for null values because the column in a table can still be NOT NULL if need be.

https://github.com/petere/pgemailaddr would be even better, but not currently available on Heroku's Postgres offering.