Hi,
I'm aware that this is a manifestation of the problem mentioned in the
Caveats subsection of the Inheritance section. I want to emphasize it,
and maybe rattle your cage a bit.
I find the Postgres notion of inheritance very compelling. Conceptually
it does what I want, when I create tables of related, but different kinds
of things.
Unfortunately these little ommissions really foul up implementations
using inheritance.
For instance: a field that REFERENCES a field in an inherited table is
unaware that records have been added to the inherited table, by way of
records being added to inheriting tables.
This is awful. One is forced to make choices between various evils.
EXAMPLE:
============================================================================
CREATE TABLE a (
a_id SERIAL PRIMARY KEY
);
CREATE TABLE a1 (
) INHERITS( a );
CREATE TABLE a2 (
) INHERITS( a );
CREATE TABLE b (
b_id SERIAL PRIMARY KEY,
a_id INTEGER,
FOREIGN KEY (a_id) REFERENCES a(a_id)
);
-- ---------------------------------------
INSERT INTO a1 VALUES( DEFAULT );
-- The following results in a foreign key violation, saying
-- no row with a_id=1 is present in table "a":
INSERT INTO b VALUES( DEFAULT, CURRVAL('a_a_id_seq') );
-- However this indicates that table "a" has a row with a_id=1:
SELECT * FROM a;
============================================================================
Cheers!
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