Gregory Stark wrote:
> I wonder if it would be more worthwhile to remove them and have a subsequent
> phase where we look for possible joins to *add*. So even if the user writes
> "select * from invoices where customer_id=?" the planner might be able to
> discover that it can find those records quicker by scanning customer, finding
> the matching <company_id,customer_id> and then using an index to look them up
> in invoices.
Yeah, that would be cool. The question is whether it's worth the
additional overhead in planner, compared to the gain in the rare case
that it's applicable. That's always the thing with planner tricks like
this. I think we'll eventually need some sort of tuning knob to control
how hard the planner tries to apply different optimizations like that.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com