[Dbix-class] Values populated by the backend - how to pull?

[James FitzGibbon]

I'm relatively new to DBIC, so hopefully there is a simple answer for this.

Given the following two classes:

package Foo;
__PACKAGE__->primary_key( 'id' );
__PACKAGE__->has_many( bars => 'Bar' => 'foo_id' );

package Bar;
__PACKAGE__->belongs_to( foo => 'Foo' => { 'foreign.id' => 'self.foo_id' }

And the following (truncated) table DDL:

CREATE TABLE foo (
	id NUMERIC(10) NOT NULL PRIMARY KEY,
);

CREATE TABLE bar (
	id NUMERIC(10) NOT NULL PRIMARY KEY,
	foo_id NUMERIC(10) NOT NULL,
	bar NUMERIC(10) NOT NULL,
	CONSTRAINT
		bar_foo_id_fk
	FOREIGN KEY(foo_id)
	REFERENCES
		foo(id)
);

The id column on the tables is populated from a sequence *by a trigger*, not
by DBIC.

I can create a Foo object without providing any attributes, because of the
trigger and default values.  If I then try to do this:

$foo = Foo->create;
$foo->add_to_bars( { bar => 1 } );

It fails with an error like this:

DBD::Oracle::st execute failed: ORA-01400: cannot insert NULL into
("BAR"."BAR_AUDIT"."FOO_ID")

This particular error is from my audit trigger, but the underlying cause is
that the Foo object I created does not have it's id field populated.  When
Bar->create_related is called, it realizes that the foo_id attribute needs
to have the value of Foo->id.  Because the value of id is only in the
database and not in the object, it's trying to populate a Bar object whose
foo_id attribute has an undef value.

My first guess is that I need to invalidate the in-memory version of the Foo
object so that when Foo->get_column('id') is called, the value from the
sequence is pulled from the database.  But there doesn't seem to be any
query code in DBIC::Row.  It's all in DBIC::Table.

Except ... I can't even use search() to discard the $foo object I have and
replace it with one borne of the database, because the in-memory $foo object
has no identifying attributes that I can use as criteria to search() or
search_like().

Am I being dumb here?  Local policy requires that the sequence values are
assigned by the database (as in "if you try to provide your own id value,
the trigger will throw an exception"), so I can't have DBIC grab the next
sequence value (which I assume would solve this problem).

I notice that that docs for DBIC::Row->get_column() say "Currently, does not
do any queries;" - is this just a shortcoming in the early DBIC releases
that at some point will be fixed?

Thanks

-- 
j.
 
James FitzGibbon
Systems Developer, Primus Telecommunications Canada Inc.
416.644.6111

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