Re: Polyphase merge is obsolete

From: vignesh C <vignesh21(at)gmail(dot)com>
To: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Peter Geoghegan <pg(at)bowt(dot)ie>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
Subject: Re: Polyphase merge is obsolete
Date: 2021-07-14 12:12:32
Message-ID: CALDaNm3K8iZh7zGKrSNHb4crGRdn3LsudgtEa=+Oz4LQE0SJOQ@mail.gmail.com
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On Sat, Jan 23, 2021 at 3:49 AM Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
>
> On 22/10/2020 14:48, Heikki Linnakangas wrote:
> > On 11/09/2017 13:37, Tomas Vondra wrote:
> >> I planned to do some benchmarking on this patch, but apparently the
> >> patch no longer applies. Rebase please?
> >
> > Here's a rebase of this. Sorry to keep you waiting :-).
>
> Here's an updated version that fixes one bug:
>
> The CFBot was reporting a failure on the FreeBSD system [1]. It turned
> out to be an out-of-memory issue caused by an underflow bug in the
> calculation of the size of the tape read buffer size. With a small
> work_mem size, the memory left for tape buffers was negative, and that
> wrapped around to a very large number. I believe that was not caught by
> the other systems, because the other ones had enough memory for the
> incorrectly-sized buffers anyway. That was the case on my laptop at
> least. It did cause a big slowdown in the 'tuplesort' regression test
> though, which I hadn't noticed.
>
> The fix for that bug is here as a separate patch for easier review, but
> I'll squash it before committing.

The patch does not apply on Head anymore, could you rebase and post a
patch. I'm changing the status to "Waiting for Author".

Regards,
Vignesh

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