Re: PQexec() hangs on OOM

On Mon, Apr 6, 2015 at 10:46 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Michael Paquier <michael.paquier@gmail.com> writes:
>> Second idea: return a status with parseInput as it is not part of the APIs
>> of libpq.
>
> Yeah; most subroutines in libpq have a zero-or-EOF return convention,
> we can make parseInput do likewise.  I'm not sure if that'd need to
> propagate further down though ...

So, I have been looking at that in more details, and finished with the
patch attached that makes the problem go away for me with a nice "out
of memory" error. I have extended parseInput() to have it return a
status code to decide if parsing should be stopped or should continue.
Note that I have tried to be careful to make a clear distinction
between cases where routines return EOF because of not enough data
parsed and actual OOMs.

I have noticed as well that getCopyStart() in fe-protocol3.c needs to
be made a little bit smarter to make the difference between an OOM and
the not-enough-data type of problem.

This problem has a low probability to happen in the field, and no
people complained about that as well, so I think that patching only
HEAD is adapted.
Regards,
--
Michael