On Thu, Aug 16, 2012 at 4:40 PM, Heikki Linnakangas < heikki.linnakan...@enterprisedb.com> wrote:
> On 15.08.2012 11:34, Alexander Korotkov wrote: > >> 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. New version of patch. * Collect new stakind STATISTIC_KIND_BOUNDS_HISTOGRAM, which is lower and upper bounds histograms combined into single ranges array, instead of STATISTIC_KIND_HISTOGRAM. * Selectivity estimations for >, >=, <, <=, <<, >>, &<, &> using this histogram. ------ With best regards, Alexander Korotkov.
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