Обсуждение: Inheritance

Hi, I'm new on postgres and I've just installed postgres 7.4.7 on a
debian sarge. I'm interested on using inheritance. I've tried a simple code:

CREATE TABLE t_main (
    id              serial          primary key
);

CREATE TABLE t_derived1 (
    field1          varchar(128)    default NULL
) INHERITS (t_main);

Now I have to create another table having a field having a reference to
t_derived1. If I use the code
CREATE TABLE t_table1 (
    id              serial          primary key,
    id_derived1     int             references t_derived1
);
I got an error:  t_derived1 have no primary key... and in effect is
t_main that have the primary key... So I modified the code in
CREATE TABLE t_table1 (
    id              serial          primary key,
    id_derived1     int             references t_main
);
and now all seems to work so I inserted a record on t_derived1

INSERT INTO t_derived1
    (field1) VALUES ('field1 content of derived1 table');

and a record in t_table1 that have a reference to the record I've just
inserted:

INSERT INTO t_table1
    (id_derived1) VALUES (1);

but I've got the error 'ERROR:  insert or update on table "t_table1"
violates foreign key constraint "$1"
DETAIL:  Key (id_derived1)=(1) is not present in table "t_main".'

So I ask you: there is a way to reference a record to an hinherited table?

Thank you very much

Piviul

Jebus scrisse in data 03/27/06 19:03:

>I could be wrong but primary keys and other constraints are not inherited.
>
>
Thank you very much Jebus; in effect I've found in the mailing list
archives a 2003 thread "INHERITS and Foreign keys" that claim the same
problem. Someone (Stephan Szabo) answered saying that "At some point in
the future, that's likely to change"
(http://archives.postgresql.org/pgsql-sql/2003-12/msg00101.php). Now I'm
using postgres 7.4.7 and I've found the same problem; do you know if
this problem is solved in postgres 8.1?

Thank you very much

Piviul

> Jebus scrisse in data 03/27/06 19:03:
>
> >I could be wrong but primary keys and other constraints are not inherited.
do you know if
> this problem is solved in postgres 8.1?

No it isn't.  But I remember reading on one of the lists that it was on the to-do list for 8.2.
However, I do not know how high it is on the list of things to do.  So I imagine that there is the
potential that it might not be added.

Regards,

Richard Broersma Jr.

Richard Broersma Jr scrisse in data 03/28/06 15:18:

>No it isn't.  But I remember reading on one of the lists that it was on the to-do list for 8.2.
>However, I do not know how high it is on the list of things to do.  So I imagine that there is the
>potential that it might not be added.
>
I'll wait 8.2 or 8.3.

Thank you very much.

Piviul