Re: [PERFORM] Concurrency issue under very heay loads

>-----Original Message-----
>From: pgsql-performance-owner(at)postgresql(dot)org
>
>We use a typical counter within a transaction to generate
>order sequence number and update the next sequence number.
>This is a simple next counter - nothing fancy about it. When
>multiple clients are concurrently accessing this table and
>updating it, under extermely heavy loads in the system (stress
>testing), we find that the same order number is being
>generated for multiple clients. Could this be a bug? Is there
>a workaround? Please let me know.

Are you using "for update" in your select statements? Are you setting
an appropriate transaction isolation level?

A better way to do this is with a sequence instead. This is guaranteed
to give you a unique value:
select nextval('address_serial_num_seq');

eric