On 15.08.2012 11:34, Alexander Korotkov wrote:
On Wed, Aug 15, 2012 at 12:14 PM, Heikki Linnakangas<
heikki.linnakan...@enterprisedb.com> wrote:
Histogram of upper bounds would be both more
accurate and natural for some operators. However, it requires collecting
additional statistics while AFAICS it doesn't liberate us from having
histogram of range lengths.
Hmm, if we collected a histogram of lower bounds and a histogram of upper
bounds, that would be roughly the same amount of data as for the "standard"
histogram with both bounds in the same histogram.
Ok, we've to decide if we need "standard" histogram. In some cases it can
be used for more accurate estimation of< and> operators.
But I think it is not so important. So, we can replace "standard" histogram
with histograms of lower and upper bounds?
Yeah, I think that makes more sense. The lower bound histogram is still
useful for < and > operators, just not as accurate if there are lots of
values with the same lower bound but different upper bound.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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