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Re: Improve compression speeds in pg_lzcompress.c

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Takeshi Yamamuro <yamamuro(dot)takeshi(at)lab(dot)ntt(dot)co(dot)jp>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Improve compression speeds in pg_lzcompress.c
Date: 2013-01-07 21:07:51
Message-ID: CA+TgmobGAf30i-FJkQfjsjQ6OYdn7b_eg+6Wk8R91sqMjispkA@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Mon, Jan 7, 2013 at 11:16 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Why would that be a good tradeoff to make?  Larger stored values require
> more I/O, which is likely to swamp any CPU savings in the compression
> step.  Not to mention that a value once written may be read many times,
> so the extra I/O cost could be multiplied many times over later on.

I agree with this analysis, but I note that the test results show it
actually improving things along both parameters.

I'm not sure how general that result is.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


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