savepoint and rollback queries in postgres

We are in the process of moving to Postgres from Oracle. We were using
"savepoint xyz" and "rollback to savepoint xyz" with Oracle. Or these
supported by Postgres?, if so what are the equivalent queries in postgres
for the same.

No, they're not supported in any released version. Postgres doens't have
savepoints and hence doesn't have nested transactions. However, there are
moves afoot and such functionality may appear in 7.3 or 7.4.

Chris