Postgres Pro
Downloads
Home   >   mailing lists

Re: Statistics and selectivity estimation for ranges - Mailing list pgsql-hackers

From Alexander Korotkov
Subject Re: Statistics and selectivity estimation for ranges
Date
Msg-id CAPpHfdsPCcCERxywysaYoPUjk3OE6dM9Mm_4Yr86OkAJsSfuHA@mail.gmail.com
Whole thread Raw
In response to Re: Statistics and selectivity estimation for ranges  (Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>)
Responses Re: Statistics and selectivity estimation for ranges
Re: Statistics and selectivity estimation for ranges
Re: Statistics and selectivity estimation for ranges
List pgsql-hackers
Tree view
On Wed, Aug 15, 2012 at 12:14 PM, Heikki Linnakangas <heikki.linnakangas@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?

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

pgsql-hackers by date:

Previous
From: Heikki Linnakangas
Date:
Subject: Re: Statistics and selectivity estimation for ranges
Next
From: "Etsuro Fujita"
Date:
Subject: Don't allow relative path for copy from file