Re: Optimizer questions

On Wed, Jan 6, 2016 at 12:08 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> konstantin knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru> writes:
> > 1. The cost compared in grouping_planner doesn't take in account price
> of get_authorized_users - it is not changed when I am altering function
> cost. Is it correct behavior?
>
> The general problem of accounting for tlist eval cost is not handled very
> well now, but especially not with respect to the idea that different paths
> might have different tlist costs. I'm working on an upper-planner rewrite
> which should make this better, or at least make it practical to make it
> better.
>

Hmm... Besides costing it would be nice to postpone calculation of
expensive tlist functions after LIMIT.

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company