Re: Statistics and selectivity estimation for ranges

On Thu, Aug 16, 2012 at 4:40 PM, Heikki Linnakangas <
heikki(dot)linnakangas(at)enterprisedb(dot)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.