fetching unique pins in a high-transaction environment...

Hi,

We are in the process of porting an application from SQL Server to
PostgresQL.

We have a table which contains a bunch of prepaid PINs. What is the
best way to fetch the next available unique pin from the table in a
high-traffic environment with lots of concurrent requests?

For example, our PINs table might look like this and contain thousands
of records. (FYI, the PIN numbers are generated by a third party and
loaded into the table):

ID PIN USED_BY DATE_USED
....
100 1864678198
101 7862517189
102 6356178381
....

10 users request a pin at the same time. What is the easiest/best way
to ensure that the 10 users will get 10 unique pins, while eliminating
any waiting?

SQL Server supports the notion of a SELECT FOR UPDATE with a READPAST
hint which tells SQL Server to skip over locked rows instead of waiting
until the lock is lifted. This guarantees a unique pin will be
acquired every time without hampering performance.

Is there any equivalent in Postgres?

Any help would be greatly appreciated...