State of the art for foreign keys to child tables?

From: François Beausoleil <francois(at)teksol(dot)info>
To: Postgres List <pgsql-general(at)postgresql(dot)org>
Subject: State of the art for foreign keys to child tables?
Date: 2012-09-18 03:15:05
Message-ID: FCA911B9-63F8-4E21-92B4-E93BB39063E7@teksol.info
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What's the state of the art for foreign keys on child tables?

My use case is this:

CREATE TABLE parties(party_id serial primary key);
CREATE TABLE positions( PRIMARY KEY(party_id) ) INHERITS(parties);
CREATE TABLE organizations( PRIMARY KEY(party_id) ) INHERITS(parties);
CREATE TABLE party_names( party_id int REFERENCES parties, surname text, PRIMARY KEY(party_id, surname) );

INSERT INTO organizations VALUES (1);
INSERT INTO party_names VALUES (1, 'foo');

This currently fails with:

ERROR: insert or update on table "party_names" violates foreign key constraint "party_names_party_id_fkey"
DETAIL: Key (party_id)=(1) is not present in table "parties".

I found http://stackoverflow.com/questions/10252603/parent-and-child-table-foreign-key which suggests using something like this:

CREATE RULE parties_ref
AS ON INSERT TO party_names
WHERE new.party_id NOT IN (SELECT party_id FROM parties)
DO INSTEAD NOTHING;

When using that and no foreign key reference, then the INSERT "succeeds" in inserting 0 records, which doesn't raise an exception... Then I found older posts on this mailing list:

http://postgresql.1045698.n5.nabble.com/Foreign-keys-to-inherited-tables-td1900234.html
http://postgresql.1045698.n5.nabble.com/Inheritance-on-foreign-key-td1924951.html
http://postgresql.1045698.n5.nabble.com/Partitioned-Tables-Foreign-Key-Constraints-Problem-td2066267.html

These mention using triggers to reproduce foreign key checks.

Is that information still current as of 9.2?

Thanks!
François

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