id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
15682	Postgresql last_insert_id() failing when using custom schemas	Anssi Kääriäinen	nobody	"Define a table like this:

{{{
create sequence foobar;
CREATE TABLE test (
    id integer not null primary key default nextval('foobar')
);
}}}

And a model like this:

{{{
class TestM(models.Model):
    pass
    class Meta:
         db_table = 'test'
}}}

In the shell, try this:

{{{
>>> t = TestM()
>>> t.save()
>>> t.id is None
True
}}}

The error here is that postgresql's last_insert_id is defined like this:
{{{
def last_insert_id(self, cursor, table_name, pk_name):
        # Use pg_get_serial_sequence to get the underlying sequence name
        # from the table name and column name (available since PostgreSQL 8)
        cursor.execute(""SELECT CURRVAL(pg_get_serial_sequence('%s','%s'))"" % (
            self.quote_name(table_name), pk_name))
        return cursor.fetchone()[0]
}}}

Now, what happens here is that pg_get_serial_sequence('test', 'id') will return NULL, and so will currval(NULL).

This is backwards incompatible as the same code would have worked in 1.2. Though I don't think it is documented anywhere that the above should work.

One possible fix is to throw an error if None is returned by cursor.fetchone()[0] above and also document in the release notes that if you have a database defined like this, you should issue a query:

ALTER SEQUENCE foobar OWNED BY test, id;

This will unfortunately not work if the sequence is used by multiple tables, as a sequence can only be owned by one column at a time.

The best fix would be to allow setting the sequence name as an Meta option in the table (as in #13295), but it is way too late for 1.3.

Related open tickets are at least #13179, #1946, #13295"	Bug	closed	Database layer (models, ORM)	1.3	Normal	duplicate	regression	inactivist@…	Unreviewed	0	0	0	0	0	0