On 01/07/2013 04:19 PM, Tom Lane wrote:
Robert Haas <robertmh...@gmail.com> writes:
On Mon, Jan 7, 2013 at 11:16 AM, Tom Lane <t...@sss.pgh.pa.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.
Hm ... one of us is reading those results backwards, then.
I just went back and looked. Unless I'm misreading it he has about a 2.5
times speed improvement but about a 20% worse compression result.
What would be interesting would be to see if the knobs he's tweaked
could be tweaked a bit more to give us substantial speedup without
significant space degradation.
cheers
andrew
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