Finding PrimaryKey columns of a table

The following may help, substitiuting "tablename";

select a.attname
from pg_index i, pg_attribute a
where i.indrelid =
(select oid as class_oid from pg_class where relname = 'tablename')
and i.indkey[0] = a.attnum
and a.attrelid = i.indrelid
and i.indisprimary = 't';

swalker writes:

Is there a query I can run against the pg system tables to figure out what
columns of the table make up the primary key?

I've messed around w/ psql -E (which is very cool btw) and can't seem to
find the exact query I'm looking for. I can get all indexes for a table,
but I can't seem to limit the result set to only the primary key.

Am I missing something obvious ?

Thanks
Steve

--
Rex McMaster rex@mcmaster.wattle.id.au
http://www.compsoft.com.au/~rmcm/pgp-pk