Re: Performance Improvement by reducing WAL for Update Operation

From: Amit kapila <amit(dot)kapila(at)huawei(dot)com>
To: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, "hlinnakangas(at)vmware(dot)com" <hlinnakangas(at)vmware(dot)com>, "noah(at)leadboat(dot)com" <noah(at)leadboat(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Performance Improvement by reducing WAL for Update Operation
Date: 2013-01-11 17:30:16
Message-ID: 6C0B27F7206C9E4CA54AE035729E9C383BEAFFB1@szxeml509-mbs
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On Friday, January 11, 2013 7:59 PM Alvaro Herrera wrote:
Simon Riggs wrote:
> On 28 December 2012 10:21, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>

> I was also worried about the high variance in the results. Those
> averages look rather meaningless. Which would be okay, I think, because
> it'd mean that performance-wise the patch is a wash,

For larger tuple sizes (>1000 && < 1800), the performance gain will be good.
Please refer performance results by me and Kyotaro-san in below links:

http://archives.postgresql.org/message-id/6C0B27F7206C9E4CA54AE035729E9C383BEAAE32@szxeml509-mbx
http://archives.postgresql.org/message-id/20121228.170748.90887322.horiguchi.kyotaro@lab.ntt.co.jp

In fact, I believe for all tuples with length between 200 to 1800 bytes and changed values around 15~20%, there will be both performance gain as well as WAL reduction.
The reason for keeping the logic same for smaller tuples (<=128 bytes) also same, that there is no much performance difference but still WAL reduction gain is visible.

> but it is still achieving a lower WAL volume, which is good.

With Regards,
Amit Kapila.

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