From: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Philip Warner <pjw(at)rhyme(dot)com(dot)au> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Zeugswetter Andreas IZ5 <Andreas(dot)Zeugswetter(at)telecom(dot)at>, pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: Selectivity of "=" (Re: [HACKERS] Index not used on simple se lect) |
Date: | 1999-07-29 02:39:03 |
Message-ID: | 199907290239.WAA27377@candle.pha.pa.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
> FWIW, statisticians often seem worried about three values: the mean, median
> and mode. I don't really know which is which, but they are:
>
> o The average of all values
> o The average of the min and max value
We have this value. Good for > and < comparisons.
> o The most common value.
We know the number of times the most common value occurs, but not the
actual value.
>
> Someone who knows a lot more about this stuff than me can probably tell us
> how these values will affect the trust we place in the index statistics.
> Someone on this list must be able to give us some insight???
>
>
> ----------------------------------------------------------------
> Philip Warner | __---_____
> Albatross Consulting Pty. Ltd. |----/ - \
> (A.C.N. 008 659 498) | /(@) ______---_
> Tel: +61-03-5367 7422 | _________ \
> Fax: +61-03-5367 7430 | ___________ |
> Http://www.rhyme.com.au | / \|
> | --________--
> PGP key available upon request, | /
> and from pgp5.ai.mit.edu:11371 |/
>
--
Bruce Momjian | http://www.op.net/~candle
maillist(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
From | Date | Subject | |
---|---|---|---|
Next Message | Ryan Kirkpatrick | 1999-07-29 03:18:23 | Re: [PORTS] RedHat6.0 & Alpha |
Previous Message | Philip Warner | 1999-07-29 02:37:05 | Re: Selectivity of "=" (Re: [HACKERS] Index not used on simple se lect) |