Re: Statistics and selectivity estimation for ranges

Alexander Korotkov <aekorotkov@gmail.com>

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From: Alexander Korotkov <aekorotkov@gmail.com>

To: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>

Cc: pgsql-hackers <pgsql-hackers@postgresql.org>

Date: 2012-08-12T21:11:51Z

Lists: pgsql-hackers

Attachments

range_stat-0.4.patch.gz (application/x-gzip) patch

On Thu, Aug 9, 2012 at 12:44 AM, Alexander Korotkov <aekorotkov@gmail.com>wrote:

> My conclusion is so, that current errors are probably ok for selectivity
> estimation. But taking into attention that generated datasets ideally fits
> assumptions of estimation, there could be room for improvement. Especially,
> it's unclear why estimate for "<@" and "@>" have much greater error than
> estimate for "&&". Possibly, it's caused by some bugs.
>

ITSM, I found reason of inaccuracy. Implementation of linear interpolation
was wrong. Fixed version is attached. Now, need to rerun tests, possible
refactoring and comments rework.

------
With best regards,
Alexander Korotkov.