SQLDA or UPDATE WHERE CURRENT OF

Hello,

I have some problems with Postgresql. I have to update much data in a
table. There are two solution for this problem in Oracle or Informix.
These two solution are SQLDA structure, or a cursor which is updatable
by using UPDATE WHERE CURRENT OF  statement. As I know, there hasn't
implemented any of these two methods yet. How can I solve my problem?
The solution must be very fast.

Thank you in advance!

Gyuri