Re: PQExec returns null question

Tom,
Thanks for the reply. I had thought we were testing for loss of connection before we send a query, but it doesn’t appear that we are. I’ll go back and look at the postmaster log to see if I can find more information. I’ll also check to see if there’s a way to really test connection before we send a query.

Regards,
Don

On Oct 20, 2014, at 10:31 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Donald Carlile <carlile(at)me(dot)com> writes:
>> Our OS X application uses PostgreSQL as a back end through pqlib. Some of our customers are reporting occasional PGRES_FATAL_ERRORs, but PQresultErrorMessage returns a blank string. I have looked at the sources, and as far as I can tell, this condition can only occur when PQExec returns a null. The docs say that this shouldn’t happen except in out of memory conditions. I am not using any Copy actions.
>> I have two broad questions. 1) What can I do to prevent this from happening? 2) If it does happen, how can I remedy it?
>
> There's a recent bug report
> http://www.postgresql.org/message-id/20141019003736.2662.84048@wrigleys.postgresql.org
> suggesting that this might happen after a loss of connection. It'd be a
> libpq bug that it's not providing a more useful error message in such a
> case, but probably the more interesting question from your standpoint
> is why is the server dropping the connection. Have you looked into the
> postmaster log to see if anything gets logged when this happens?
>
> If it's not a connection-loss case then you've found some new bug that
> we ought to look into, but without a reproducible test case it's hard
> to do much in that line.
>
> regards, tom lane