On Friday 13 October 2006 12:46, Gregory Stark wrote:
> Josh Berkus <josh@agliodbs.com> writes:
> >> > I actually think the way to attack this issue is to discuss the kinds
> >> > of errors the planner makes, and what tweaks we could do to correct
> >> > them. Here's the ones I'm aware of:
> >> >
> >> > -- Incorrect selectivity of WHERE clause
> >> > -- Incorrect selectivity of JOIN
> >> > -- Wrong estimate of rows returned from SRF
> >> > -- Incorrect cost estimate for index use
> >> >
> >> > Can you think of any others?
>
> -- Incorrect estimate for result of DISTINCT or GROUP BY.
Yeah, that one is bad. I also ran into one the other day where the planner
did not seem to understand the distinctness of a columns values across table
partitions...
--
Robert Treat
Build A Brighter LAMP :: Linux Apache {middleware} PostgreSQL