David Rowley <dgrowleyml@gmail.com> writes:
> On Thu, 24 Jun 2021 at 10:38, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I strongly disagree. That's essentially betting the whole farm on
>> our always being able to optimize parent-level operations fully,
>> which I do not think we are anywhere close to.
> Did you have anything in particular in mind here?
I don't think it's very hard to make up WHERE conditions that a person can
see select only one partition, but PG won't be able to figure that out.
> But... maybe there are some cases where a user can be certain that all
> interesting records are contained in a single partition but
> partitioning pruning cannot prove it...So maybe what you say is right.
> The workaround there would be to add a qual that allows pruning to
> work.
[ shrug... ] It's about as easy to just name the partition you want.
When planning overhead is considered, maybe it's a lot easier.
regards, tom lane