Re: ANALYZE sampling is too good

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