Re: cast lo to oid

"Nekta Katz" <nekta_k(at)hotmail(dot)com> writes:
> I have the following table

> create table scan_docs (
> docid serial,
> shipno numeric(10),
> scan lo,
> type text
> );

> when I try to create the following rule

> create rule "delete_scan_docs_lo" as
> on delete to "scan_docs"
> do select lo_unlink (old.scan);

Why aren't you using the trigger that type LO provides for this purpose?
Seems rather pointless to use a nonstandard type and then ignore the
primary (sole) feature it provides...

> create rule "delete_scan_docs_lo" as
> on delete to "scan_docs"
> do select lo_unlink (old.scan::oid);

> "psql:scan_docs_rule.sql:3: ERROR: Cannot cast type 'lo' to 'oid' "

Curious, as contrib/lo provides a function that's supposed to work
for that:

-- same function, named to allow it to be used as a type coercion, eg:
-- CREATE TABLE a (image lo);
-- SELECT image::oid FROM a;
--
CREATE FUNCTION oid(lo)
RETURNS oid
AS 'MODULE_PATHNAME', 'lo_oid'
LANGUAGE 'C';

What PG version are you using?

regards, tom lane