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Subject: Re: PQExec returns null question
From: Donald Carlile <carlile@me.com>
In-reply-to: <2666.1413826268@sss.pgh.pa.us>
Date: Mon, 20 Oct 2014 12:28:46 -0700
Cc: pgsql-interfaces@postgresql.org
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Message-id: <1C7ADC29-7929-4D53-AB0B-A6CC5A8263CB@me.com>
References: <D2BB3EEC-5FA7-4EB3-B232-ADBBC06590B0@me.com>
 <2666.1413826268@sss.pgh.pa.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
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Sender: pgsql-interfaces-owner@postgresql.org

Tom,
Thanks for the reply. I had thought we were testing for loss of connection =
before we send a query, but it doesn=92t appear that we are. I=92ll go back=
 and look at the postmaster log to see if I can find more information. I=92=
ll also check to see if there=92s 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 o=
f our customers are reporting occasional PGRES_FATAL_ERRORs, but PQresultEr=
rorMessage 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. T=
he docs say that this shouldn=92t 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 happen=
ing? 2) If it does happen, how can I remedy it?
>=20
> There's a recent bug report
> http://www.postgresql.org/message-id/20141019003736.2662.84048@wrigleys.p=
ostgresql.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?
>=20
> 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.
>=20
> 			regards, tom lane


--=20
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