PostgreSQL: How to create a foreign key on a table with inheritance - postgresql

Question

I'm trying to create the following tables structure:
create table base_auditoria (
ip_usuario_aud character varying(30) not null,
id_usuarioa_aud integer not null
);
create table pessoa (
id serial not null,
nome character varying not null,
constraint pk__pessoa__id primary key (id)
)
inherits (base_auditoria);
create table pessoa_fisica (
cpf character varying(11) not null,
nome_mae character varying not null
)
inherits (pessoa);
create table usuario (
id serial not null,
id_pessoa integer not null,
email character varying(500) not null,
constraint pk_usuario_id primary key (id)
)
inherits (base_auditoria);
After creating them, insert only one record in the table "usuario" and only one record in the table "pessoa_fisica":
INSERT INTO pessoa_fisica (cpf, nome_mae, nome, ip_usuario_aud, id_usuario_aud)
VALUES ('cpf 001', 'nome mae 001', 'pessoa.nome 001', '255.255.255.255', 0);
INSERT INTO usuario (id_pessoa, email, ip_usuario_aud, id_usuario_aud)
VALUES (
(SELECT id FROM pessoa_fisica WHERE cpf = 'cpf 001' LIMIT 1),
'test#test', '0.0.0.0', 0
);
So I update the two records to contain the correct identifiers that are foreign keys:
UPDATE usuario SET id_usuario_aud = id;
UPDATE pessoa_fisica SET id_usuario_aud = (SELECT id FROM usuario LIMIT 1);
When I run the SELECT, I get the expected answers:
db=# SELECT * FROM usuario;
ip_usuario_aud | id_usuario_aud | id | id_pessoa | email
----------------+----------------+----+-----------+-----------
0.0.0.0 | 1 | 1 | 1 | test#test
(1 registro)
db=# SELECT * FROM pessoa_fisica
ip_usuario_aud | id_usuario_aud | id | nome | cpf | nome_mae
-----------------+----------------+----+-----------------+---------+--------------
255.255.255.255 | 1 | 1 | pessoa.nome 001 | cpf 001 | nome mae 001
(1 registro)
ab=# SELECT * FROM pessoa;
ip_usuario_aud | id_usuario_aud | id | nome
-----------------+----------------+----+-----------------
255.255.255.255 | 1 | 1 | pessoa.nome 001
(1 registro)
ab=# SELECT * FROM ONLY pessoa;
ip_usuario_aud | id_usuario_aud | id | nome
----------------+----------------+----+------
(0 registro)
When I try to add a FOREIGN KEY constraint with the following command, I get the error:
alter table usuario
add constraint fk_1
foreign key (id_pessoa)
references pessoa (id)
match simple on update no action on delete no action;
ERROR: insert or update on table "usuario" violates foreign key constraint
"fk_1" DETAIL: Key (id_pessoa) = (1) is not present in the table
"pessoa".
How can I solve this problem?
Solution 1: Remove inheritance and work with foreign key relationships only;
Solution 2: Create a trigger to copy the table data "pessoa_fisica" to "pessoa" with the command:
CREATE OR REPLACE FUNCTION fn_tg_1() RETURNS trigger AS
$BODY$
BEGIN
IF tg_op = 'INSERT' THEN
INSERT INTO pessoa
SELECT ip_usuario_aud, id_usuario_aud, id, nome
FROM pessoa_fisica
WHERE id = new.id;
ELSIF tg_op = 'UPDATE' THEN
UPDATE pessoa SET
ip_usuario_aud = new.ip_usuario_aud,
id_usuario_aud = new.id_usuario_aud,
nome = new.nome
WHERE id = new.id;
ELSIF tg_op = 'DELETE' THEN
DELETE FROM pessoa WHERE id = new.id;
END IF;
END
$BODY$
LANGUAGE plpgsql VOLATILE COST 100;
CREATE TRIGGER tg_1
BEFORE INSERT OR UPDATE OR DELETE
ON pessoa_fisica FOR EACH ROW
EXECUTE PROCEDURE fn_tg_1();
Thus the foreign key "fk_1" can be created.
Is there any other alternative?