Re: Concurrency issue under very heay loads

Raji Sridar (raji) wrote:
> Hi,
>
> 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.

without seeing your code, its hard to say where this bug is, in your
counter implementation, or in postgres.  you also don't say what version
of postgres you're using, or even what OS you're running under...

sounds like you should be using a SERIAL (which is implemented as an
INTEGER or BIGINT field with an associated SEQUENCE), as these DO work
just fine under heavy concurrency without any gotchas.