Re: Duplicate key issue in a transaction block

On Mon, Jun 8, 2009 at 12:25 PM, Ioana Danes<ioanasoftware(at)yahoo(dot)ca> wrote:
>
> Well, I guess I have my answer...
>
> I tried to narrow down an issue I get on one of the production sites, where using a similar transaction I get the same error.
>
> In my production environment the group id is actually a unique number for the terminal (terminalid) and the same transaction CANNOT be called for the same terminalid. So this should never happen because each terminal has its own ID and this procedure is called on login operation for each terminal... At least that's what I thought so...
>
> But it does happen during the nightly online backup (pg_dump).
> It looks like when the client logs in, the request is sent from the client to the db, the backup (pg_dump) slows down the server (or holds the lock on that table?) and the user does not have patience and restarts the client and logs in again.
> In this case I can get two parallel transactions for the same terminal...

You mentioned earlier you're using slony for replication, so the
answer is obvious, run the backup against a read slave, and set the
users, during backup, to only have access to the written to master.