recursive ids

CREATE TABLE mboxes (
    id INTEGER NOT NULL,
    -- ...
    is_login_alias BOOLEAN DEFAULT FALSE NOT NULL,
    parent_id INTEGER
);

CREATE SEQUENCE seq_mboxes_id
  START WITH 1 INCREMENT BY 1 NO MINVALUE NO MAXVALUE CACHE 1;

ALTER SEQUENCE seq_mboxes_id
  OWNED BY mboxes.id;

ALTER TABLE mboxes
  ALTER COLUMN id SET DEFAULT nextval('seq_mboxes_id'::regclass);

ALTER TABLE mboxes
  ADD CONSTRAINT mboxes_pkey PRIMARY KEY (id);

ALTER TABLE mboxes
  ADD CONSTRAINT mboxes_fkey_self
  FOREIGN KEY (parent_id) REFERENCES mboxes(id) ON DELETE CASCADE;