Re: Speed dblink using alternate libpq tuple storage

On Wed, Apr 04, 2012 at 06:41:00PM -0400, Tom Lane wrote:
> Marko Kreen <markokr@gmail.com> writes:
> > On Wed, Apr 4, 2012 at 10:17 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> >> Given the lack of consensus around the suspension API, maybe the best
> >> way to get the underlying libpq patch to a committable state is to take
> >> it out --- that is, remove the "return zero" option for row processors.
>
> > Agreed.
>
> Done that way.

Minor cleanups:

* Change callback return value to be 'bool': 0 is error.
  Currently the accepted return codes are 1 and -1,
  which is weird.

  If we happen to have the 'early-exit' logic in the future,
  it should not work via callback return code.  So keeping the 0
  in reserve is unnecessary.

* Support exceptions in multi-statement PQexec() by storing
  finished result under PGconn temporarily.  Without doing it,
  the result can leak if callback longjmps while processing
  next result.

* Add <caution> to docs for permanently keeping custom callback.

  This API fragility is also reason why early-exit (if it appears)
  should not work via callback - instead it should give safer API.

--
marko