Re: Faster methods for getting SPI results

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Chapman Flack <chap(at)anastigmatix(dot)net>
Cc: Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Joe Conway <mail(at)joeconway(dot)com>, Craig Ringer <craig(at)2ndquadrant(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>, Andres Freund <andres(at)anarazel(dot)de>
Subject: Re: Faster methods for getting SPI results
Date: 2017-09-12 21:00:18
Message-ID: 13677.1505250018@sss.pgh.pa.us
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Chapman Flack <chap(at)anastigmatix(dot)net> writes:
> On 09/12/2017 03:41 PM, Tom Lane wrote:
>> So the conclusion at the end of the last commitfest was that this patch
>> should be marked Returned With Feedback, and no new work appears to have
>> been done on it since then. Why is it in this fest at all? There
>> certainly doesn't seem to be any reason to review it again.

> I'm not sure how to read the history of the CF entry. Could it
> have rolled over to 2017-09 by default if its status was simply
> never changed to Returned with Feedback as intended in the last
> one? The history doesn't seem to show anything since 2017-03-19.

Maybe, or whoever was closing out the last CF didn't notice Andres'
recommendation to mark it RWF.

> I would still advocate for a fast-callback/slow-callback distinction,
> as in
> https://www.postgresql.org/message-id/59813946.40508%40anastigmatix.net
> if that does not seem overcomplicated to more experienced hands.

I did not see any reason given in the thread why we should need that.
If you want to accumulate tuples ten at a time before you do something
with them, you can do that now, by calling ExecutorRun with count=10.
(plpgsql does something much like that IIRC.) The only reason not to
just use count=1 is that ExecutorRun and ExecutePlan have accumulated
assorted startup/shutdown cruft on the assumption that their runtime
didn't particularly matter. It still doesn't look that awful, but
it might be noticeable.

regards, tom lane

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