Re: Polyphase merge is obsolete

From: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
To: Jaime Casanova <jcasanov(at)systemguards(dot)com(dot)ec>
Cc: vignesh C <vignesh21(at)gmail(dot)com>, 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Subject: Re: Polyphase merge is obsolete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: 2021-09-15 21:35:16
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On 16/09/2021 00:12, Jaime Casanova wrote:
> On Sat, Sep 11, 2021 at 01:35:27AM -0500, Jaime Casanova wrote:
>> On Wed, Jul 14, 2021 at 06:04:14PM +0300, Heikki Linnakangas wrote:
>>> On 14/07/2021 15:12, vignesh C wrote:
>>>> On Sat, Jan 23, 2021 at 3:49 AM Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
>>>>> 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".
>>> Here's a rebased version. I also squashed that little bug fix from previous
>>> patch set.
>> Hi,
>> This patch does not apply, can you submit a rebased version?
> BTW, I'm marking this one as "waiting on author"

Thanks, here's another rebase.

- Heikki

Attachment Content-Type Size
v5-0001-Refactor-LogicalTapeSet-LogicalTape-interface.patch text/x-patch 67.8 KB
v5-0002-Replace-polyphase-merge-algorithm-with-a-simple-b.patch text/x-patch 40.8 KB

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