Re: Append with naive multiplexing of FDWs

On Thu, Dec 5, 2019 at 05:45:24PM +1300, Thomas Munro wrote:
> My patch set (rebased upthread) was extremely primitive, with no new
> planner concepts, and added only a very simple new executor node
> method: ExecReady(). Append used that to try to ask its children if
> they'd like some time to warm up. By default, ExecReady() says "I
> don't know what you're talking about, go away", but FDWs can provide
> an implementation that says "yes, please call me again when this fd is
> ready" or "yes, I am ready, please call ExecProc() now". It doesn't
> deal with anything more complicated than that, and in particular it
> doesn't work if there are extra planner nodes in between Append and
> the foreign scan. (It also doesn't mix particularly well with
> parallelism, as mentioned.)
>
> The reason I reposted this unambitious work is because Stephen keeps
> asking me why we don't consider the stupidly simple thing that would
> help with simple foreign partition-based queries today, instead of
> waiting for someone to redesign the entire executor, because that's
> ... really hard.

I agree with Stephen's request. We have been waiting for the executor
rewrite for a while, so let's just do something simple and see how it
performs.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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