Date: Wed, 27 Nov 2019 10:42:17 +0100
From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
	Andrey Borodin <x4mmm@yandex-team.ru>,
	Alvaro Herrera <alvherre@2ndquadrant.com>,
	Gasper Zejn <zejn@owca.info>, pgsql-hackers@lists.postgresql.org
Subject: Re: pglz performance
Message-ID: <20191127094217.5caghrkttntybugj@development>
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 <20191125080309.GK99720@paquier.xyz>
 <13C6049A-C3D9-4021-9934-41488DE38BE9@yandex-team.ru>
 <20191125082940.GP99720@paquier.xyz>
 <20191126094324.7y2n3n3houetavwd@development>
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On Wed, Nov 27, 2019 at 05:01:47PM +0900, Michael Paquier wrote:
>On Tue, Nov 26, 2019 at 09:05:59PM +0100, Tomas Vondra wrote:
>> Yeah, although the difference is minimal. We could probably construct a
>> benchmark where #2 wins, but I think these queries are fairly realistic.
>> So I'd just go with #1.
>
>Nice results.  Using your benchmarks it indeed looks like patch 1 is a
>winner here.
>
>> Code-wise I think the patches are mostly fine, although the comments
>> might need some proof-reading.
>>
>> 1) I wasn't really sure what a "nibble" is, but maybe it's just me and
>> it's a well-known term.
>>
>> 2) First byte use lower -> First byte uses lower
>>
>> 3) nibble contain upper -> nibble contains upper
>>
>> 4) to preven possible uncertanity -> to prevent possible uncertainty
>>
>> 5) I think we should briefly explain why memmove would be incompatible
>> with pglz, it's not quite clear to me.
>>
>> 6) I'm pretty sure the comment in the 'while (off < len)' branch will be
>> badly mangled by pgindent.
>>
>> 7) The last change moving "copy" to the next line seems unnecessary.
>
>Patch 1 has a typo as well here:
>+   * When offset is smaller than lengh - source and
>s/lengh/length/
>
>Okay, if we are reaching a conclusion here, Tomas or Peter, are you
>planning to finish brushing the patch and potentially commit it?

I'd like some feedback from Andrey regarding the results and memmove
comment, ant then I'll polish and push.

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services