Thank you all for the answers, they covered me well.
Is this worth a bug report? I can file one if the issue is not known.
No. It's just a missing optimisation. We know about it.
It's good I shot an email first then. FWIW my usual way in other projects
would be to check the bugtracker, and
David Rowley writes:
> It would be possible to have some sort of MergeExcept operator and
> have the planner consider that. Unfortunately, since the upper planner
> was changed a few years ago to have it consider paths the same as the
> join planner does, nobody has yet come back to the union plan
On Wed, 1 Nov 2023 at 11:41, Dimitrios Apostolou wrote:
> I'm wondering why the planner doesn't see that the left table is very small
> and follow a different path.
> From an abstract computer science POV, I would
>
> 1. sort the left table (the right one is already indexed)
> 2. "merge" the two
On Tue, Oct 31, 2023 at 3:41 PM Dimitrios Apostolou wrote:
>
> Is this worth a bug report? I can file one if the issue is not known.
> Or am I misunderstanding the implications of the SELECT-EXCEPT query?
>
> In the meantime I have replaced the query with a LEFT OUTER JOIN which
> performs much b
