Re: Append with naive multiplexing of FDWs

At Fri, 6 Dec 2019 10:03:44 +1300, Thomas Munro <thomas.munro@gmail.com> wrote in 
> On Fri, Dec 6, 2019 at 9:20 AM Robert Haas <robertmhaas@gmail.com> wrote:
> > I don't know whether this patch has that kind of problem. If it
> > doesn't, I would consider that a promising sign.
> 
> I'll look into that.  If there is a measurable impact, I suspect it
> can be avoided by, for example, installing a different ExecProcNode
> function.

Replacing ExecProcNode perfectly isolates additional process in
ExecAppendAsync. Thus, for pure local appends, the patch can impact
performance through only planner and execinit. But I don't believe it
cannot be as large as observable in a large scan.

As the mail pointed upthread, the patch acceleartes all remote cases
when fetch_size is >= 200. The problem was that local scans seemed
slightly slowed down. I dusted off the old patch (FWIW I attached it)
and.. will re-run on the current development environment. (And
re-check the code.).

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center