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Re: Performance Improvement by reducing WAL for Update Operation

From: Amit Kapila <amit(dot)kapila(at)huawei(dot)com>
To: "'Heikki Linnakangas'" <hlinnakangas(at)vmware(dot)com>
Cc: <simon(at)2ndquadrant(dot)com>, "'Alvaro Herrera'" <alvherre(at)2ndquadrant(dot)com>, <noah(at)leadboat(dot)com>, <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Performance Improvement by reducing WAL for Update Operation
Date: 2013-01-29 14:11:49
Message-ID: 009e01cdfe2a$9548f340$bfdad9c0$@kapila@huawei.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Tuesday, January 29, 2013 3:53 PM Heikki Linnakangas wrote:
> On 29.01.2013 11:58, Amit Kapila wrote:
> > Can there be another way with which current patch code can be made
> better,
> > so that we don't need to change the encoding approach, as I am having
> > feeling that this might not be performance wise equally good.
> 
> The point is that I don't want to heap_delta_encode() to know the
> internals of pglz compression. You could probably make my patch more
> like yours in behavior by also passing an array of offsets in the new
> tuple to check, and only checking for matches as those offsets.

I think it makes sense, because if we have offsets of both new and old
tuple, we
can internally use memcmp to compare columns and use same algorithm for
encoding.
I will change the patch according to this suggestion.

With Regards,
Amit Kapila.




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