Re: Optimization outcome depends on the index order

On Fri, Dec 22, 2023 at 7:24 PM Andrei Lepikhov
<a(dot)lepikhov(at)postgrespro(dot)ru> wrote:
> On 22/12/2023 11:48, Alexander Korotkov wrote:
> > > Because we must trust all predictions made by the planner, we just
> > > choose the most trustworthy path. According to the planner logic, it is
> > > a path with a smaller selectivity. We can make mistakes anyway just
> > > because of the nature of estimation.
> >
> > Even if we need to take selectivity into account here, it's still not
> > clear why this should be on top of other logic later in add_path().
> I got your point now, thanks for pointing it out. In the next version of
> the patch selectivity is used as a criteria only in the case of COSTS_EQUAL.

It looks better now. But it's hard for me to judge these heuristics
in add_path(). Tom, what do you think about this?

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Regards,
Alexander Korotkov