In SQLServer, you can use syntax "(nolock)" to ensure the query doesn't lock the table or isn't blocked by other queries locking the same table. e.g.
SELECT * FROM mytable (nolock) WHERE id = blah
What's the equivalent syntax in Postgres? I found some documentation on table locking in PG (http://www.postgresql.org/docs/8.1/interactive/sql-lock.html), but it all seems geared at how to lock a table, not ensure it's not locked.
A SELECT doesn't lock any table in PostgreSQL, unless you want a lock:
SELECT * FROM tablename FOR UPDATE;
PostgreSQL uses MVCC to minimize lock contention in order to allow for reasonable performance in multiuser environments. Readers do not conflict with writers nor other readers.