Re: Is it possible to specify minimum number of rows planner should consider?

Here is a commit that accomplishes this with a configuration parameter.

https://github.com/labkey-matthewb/postgres/commit/b1fd99f4deffbbf3db2172ccaba51a34f18d1b1a

On Mon, Sep 28, 2020 at 2:07 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Timothy Garnett <tgarnett(at)panjiva(dot)com> writes:
> > Is there some way to tell the planner that unless it's guaranteed by a
> > constraint or some such it shouldn't guess that the selectivity of a
> > filter/anti-join is 1 row (e.g. minimum to consider is 2 rows unless it's
> > guaranteed to be 1 row) or somehow otherwise make it more conservative
> > around the worst case possibilities.
>
> There's been some discussion in that area, but it's a hard problem
> to solve in general, and especially so if you'd like to not break
> a ton of queries that work nicely today.
>
> regards, tom lane
>
>
>