RE: Query bombed: why?

Thanks for your reply.
I was expecting not much more than 50 rows to be returned, with an absolute
maximum of 70.
I was trying to simulate an outer join by using the "where not exists"
clause, so that I would get back my full list of 70 and be able to see the
unmatched entries...

> -----Original Message-----
> From: Tom Lane [SMTP:tgl(at)sss(dot)pgh(dot)pa(dot)us]
> Sent: Tuesday, May 09, 2000 12:35 PM
> To: Jeff Eckermann
> Cc: pgsql-general(at)postgresql(dot)org
> Subject: Re: [GENERAL] Query bombed: why?
>
> Jeff Eckermann <jeckermann(at)verio(dot)net> writes:
> > After about 25 minutes of running a query with a "where not exists
> > 'correlated subquery'", I got a whole bunch of lines printing out:
> "Backend
> > sent D message without prior T".
> > Could someone give me an idea of what that means, and how to deal with
> it?
>
> How many rows were you expecting the query to produce? (It might be
> worth redoing it as a SELECT count(*) FROM ... to find out how many it
> really produced.) My first bet is that your frontend application ran
> out of memory while trying to absorb the query result. libpq is
> designed to collect the whole result before handing it back to the
> application, which is nice for some things but starts to look like a bad
> idea when you have a huge query result. Also, libpq doesn't react very
> gracefully to running out of memory :-( --- the symptoms you describe
> sound like one likely failure mode. (We need to fix that...)
>
> You might be able to increase your process memory limit; otherwise,
> consider using DECLARE CURSOR and FETCH to retrieve the query result
> a few hundred rows at a time.
>
> regards, tom lane