Re: Simple postgresql.conf wizard

Jonah H. Harris wrote:
> Oracle already thought of that a long time ago, which is why the plan
> has to come out better for it to take effect.

Huh? We would never willingly choose a worse plan, of course, but the 
point is that what looks like a better plan, with a smaller cost 
estimate, is sometimes actually worse.

>  As for bad plans, you
> obviously haven't used Postgres in production enough to deal with it
> continually changing plans for the worse due to index bloat, data
> skew, phase of the moon, etc. :)

You're right, I haven't, but yes I know that's a problem. We've chatted 
about that with Greg sometimes. It would be nice to have more stable 
plans. My favorite idea is to stop using the current relation size in 
the planner, and use the value snapshotted at ANALYZE instead. That way, 
the planner would be completely deterministic, based on the statistics. 
Then, we could have tools to snapshot the statistics, move them to a 
test system, store them, revert back to old statistics etc.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com