Re: Problem Using PQcancel in a Synchronous Query

Tom,

That was it! My implementation of cancel() was swallowing the result
message. Thanks so much, I've got it working now.

--
Eric Simon
The IQ Group, Inc.

-----Original Message-----
From: pgsql-hackers-owner(at)postgresql(dot)org
[mailto:pgsql-hackers-owner(at)postgresql(dot)org] On Behalf Of Tom Lane
Sent: Monday, August 23, 2010 7:06 PM
To: Eric Simon
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: [HACKERS] Problem Using PQcancel in a Synchronous Query

"Eric Simon" <esimon(at)theiqgroup(dot)com> writes:
> Now that I've established some context, here's where I'm at: I've written
> $sth->cancel() for DBD::Pg using PQcancel(), and it works (it returns the
> status 57014: QUERY CANCELED). The problem is that the $sth->execute call
> (which resides between the two alarm() calls above) doesn't continue on,
but
> rather stays frozen, waiting for data. Does PQcancel not communicate back
> to the execute statement so that it unblocks?

Um ... PQcancel returns no such thing, only true or false. I'm guessing
you've coded your signal handler in such a way that it eats the query
result message intended for the mainline execute code. You should not
be calling anything except PQcancel itself in the signal handler.

regards, tom lane