Why does this foreign key using inheritance not work? [duplicate] - postgresql

Question

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PostgreSQL foreign key not existing, issue of inheritance?
(2 answers)
Closed 8 years ago.
create table abstract_addresses (
address_id int primary key
);
create table phone_numbers (
phone_number text not null unique
) inherits (abstract_addresses) ;
create table contacts (
name text primary key,
address_id int not null references abstract_addresses(address_id)
);
insert into phone_numbers values (1, '18005551212'); --works
select * from abstract_addresses;
address_id
1
select * from phone_numbers;
address_id phone_number
1 18005551212
insert into contacts values ('Neil', 1); --error
I get this error message:
ERROR: insert or update on table "contacts" violates foreign key constraint "contacts_address_id_fkey"
SQL state: 23503
Detail: Key (address_id)=(1) is not present in table "abstract_addresses".
Just a bad use-case for postgresql table inheritance?

Answer 1

Per the caveats in the docs:
A serious limitation of the inheritance feature is that indexes (including unique constraints) and foreign key constraints only apply to single tables, not to their inheritance children. This is true on both the referencing and referenced sides of a foreign key constraint.
http://www.postgresql.org/docs/current/static/ddl-inherit.html
To do what you want:
Create a table with only an id — like you did.
Don't use inheritance. Really don't. It's useful to partition log tables; not for what you're doing.
Make phone number ids default to nextval('abstract_addresses_address_id_seq'), or whatever the sequence name is.
Add a foreign key in phone_numbers referencing abstract_addresses (address_id). Make it deferrable, initially deferred.
Add an after insert trigger on phone_numbers that inserts a new row in abstract_addresses when needed.
If appropriate, add an after delete trigger on phone_numbers that cascade deletes abstract_addresses — make sure it occurs after the delete, else affected rows will report incorrect values when you delete from phone_numbers.
That way, you'll have an abstract_address for use in occasional tables that need such a thing, while still being able to have a hard reference to phone_numbers where the latter is what you actually want.
One caveat to be aware of: it doesn't play well with ORMs.