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Re: Statistics and selectivity estimation for ranges

From: Alexander Korotkov <aekorotkov(at)gmail(dot)com>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Statistics and selectivity estimation for ranges
Date: 2012-08-12 21:11:51
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Lists: pgsql-hackers
On Thu, Aug 9, 2012 at 12:44 AM, Alexander Korotkov <aekorotkov(at)gmail(dot)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.

Attachment: range_stat-0.4.patch.gz
Description: application/x-gzip (10.4 KB)

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