Re: Performance Improvement by reducing WAL for Update Operation

On Friday, January 11, 2013 7:59 PM Alvaro Herrera wrote:
Simon Riggs wrote:
> On 28 December 2012 10:21, Simon Riggs <simon@2ndquadrant.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.