Re: Planner hints in Postgresql

* Atri Sharma (atri(dot)jiit(at)gmail(dot)com) wrote:
> Isnt using a user given value for selectivity a pretty risky situation as
> it can horribly screw up the plan selection?
>
> Why not allow the user to specify an alternate plan and have the planner

Uh, you're worried about the user given us a garbage selectivity, but
they're going to get a full-blown plan perfect?

> assign a higher preference to it during plan evaluation? This shall allow
> us to still have a fair evaluation of all possible plans as we do right now
> and yet have a higher preference for the user given plan during evaluation?

What exactly would such a "preference" look like? A cost modifier?
We'd almost certainly have to make that into a GUC or a value passed in
as part of the query, with a high likelihood of users figuring out how
to use it to say "use my plan forever and always"..

Thanks,

Stephen