On Wed, Dec 20, 2017 at 4:20 PM, Jeff Janes <jeff.ja...@gmail.com> wrote: > > It is not obvious to me that the parabola is wrong. I've certainly seen > cases where reading every 2nd or 3rd block (either stochastically, or > modulus) actually does take longer than reading every block, because it > defeats read-ahead. But it depends on a lot on your kernel version and > your kernel settings and your file system and probably other things as well. >
Well, that's an interesting point, too. Maybe we need another graph that also shows the actual runtime of a bitmap scan and a sequential scan. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
