On Tue, Aug 13, 2019 at 3:18 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> Robert Haas <robertmhaas@gmail.com> writes:
> > Being able to do that sort of thing was one of my goals in designing
> > the ExecShutdownNode stuff. Unfortunately, it's clear from this bug
> > report that it's still a few bricks short of a load, and Tom doesn't
> > seem real optimistic about how easy it will be to buy those bricks at
> > discount prices. But I hope we persist in trying to get there, because
> > I don't like the idea of saying that we'll never be smart enough to
> > know we're done with any part of the plan until we're definitely done
> > with the whole thing. I think that's leaving too much money on the
> > table.
>
> To clarify my position --- I think it's definitely possible to improve
> the situation a great deal. We "just" have to pass down more information
> about whether rescans are possible.
>
Right, you have speculated above that it is possible via adding some
eflag bits. Can you please describe a bit more about that idea, so
that somebody else can try to write a patch? I think if someone other
than you try to write a patch without having some sort of upfront
design, it might lead to a lot of re-work. It would be great if you
have an interest in doing the leg work which can then be extended to
fix the issue in the parallel query, but if not at least let us know
the idea you have in mind in a bit more detail.
> What I don't believe is that that
> leads to a bug fix that would be sane to back-patch as far as 9.6.
>
Fair enough. In such a situation, we can plan to revert the earlier
fix for Limit node and tell people that the same will be fixed in
PG-13.
--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com