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@sss.pgh.pa.us> wrote:

Timothy Garnett <tgarnett@panjiva.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