Richard Guo <guofengli...@gmail.com> writes:
> On Fri, Nov 17, 2023 at 11:38 AM Tom Lane <t...@sss.pgh.pa.us> wrote:
>> That line of argument also leads to the conclusion that it'd be
>> okay to expose info about the ordering of the CTE result to the
>> upper planner.
> In the light of this conclusion, I had a go at propagating the pathkeys
> from CTEs up to the outer planner and came up with the attached.
Oh, nice! I remembered we had code already to do this for regular
SubqueryScans, but I thought we'd need to do some refactoring to
apply it to CTEs. I think you are right though that
convert_subquery_pathkeys can be used as-is. Some thoughts:
* Do we really need to use make_tlist_from_pathtarget? Why isn't
the tlist of the cteplan good enough (indeed, more so)?
* I don't love having this code assume that it knows how to find
the Path the cteplan was made from. It'd be better to make
SS_process_ctes save that somewhere, maybe in a list paralleling
root->cte_plan_ids.
Alternatively: maybe it's time to do what the comments in
SS_process_ctes vaguely speculate about, and just save the Path
at that point, with construction of the plan left for createplan()?
That might be a lot of refactoring for not much gain, so not sure.
regards, tom lane
