Re: ANALYZE sampling is too good

On 12/12/13 08:31, Kevin Grittner wrote:
> Gavin Flower <GavinFlower@archidevsys.co.nz> wrote:
>
>> For example, assume 1000 rows of 200 bytes and 1000 rows of 20 bytes,
>> using 400 byte pages.  In the pathologically worst case, assuming
>> maximum packing density and no page has both types: the large rows would
>> occupy  500 pages and the smaller rows 50 pages. So if one selected 11
>> pages at random, you get about 10 pages of large rows and about one for
>> small rows!
> With 10 * 2 = 20 large rows, and 1 * 20 = 20 small rows.
>
> --
> Kevin Grittner
> EDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
Sorry, I've simply come up with well argued nonsense!

Kevin, you're dead right.


Cheers,
Gavin