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
appearthat we are. I’ll go back and look at the postmaster log to see if I can find more information. I’ll also check
tosee 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@sss.pgh.pa.us> wrote:

> Donald Carlile <carlile@me.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
memoryconditions. 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