RE: [HACKERS] Some notes on optimizer cost estimates

> -----Original Message-----
> From: owner-pgsql-hackers@postgreSQL.org
> [mailto:owner-pgsql-hackers@postgreSQL.org]On Behalf Of Tom Lane
> 
> I have been spending some time measuring actual runtimes for various
> sequential-scan and index-scan query plans, and have learned that the
> current Postgres optimizer's cost estimation equations are not very
> close to reality at all.
> 

Thanks for your good analysis.

I also have said current cost estimation for index-scan is too low.
But I have had no concrete numerical values.

I've wondered why we cound't analyze database without vacuum.
We couldn't run vacuum light-heartedly because it acquires an
exclusive lock for the target table. 
In addition,vacuum error occurs with analyze option in most
cases AFAIK. 

Regards.

Hiroshi Inoue
Inoue@tpf.co.jp