David Rowley <dgrowle...@gmail.com> writes:
> On Wed, 12 Jul 2023 at 14:50, David Rowley <dgrowle...@gmail.com> wrote:
>> On Wed, 12 Jul 2023 at 14:23, Tom Lane <t...@sss.pgh.pa.us> wrote:
>>> I did think about that, but "shallow copy a Path" seems nontrivial
>>> because the Path structs are all different sizes. Maybe it is worth
>>> building some infrastructure to support that?
>> It seems a reasonable thing to have to do. It seems the minimum thing
>> we could do to ensure each Path is only mentioned in at most 1
>> RelOptInfo.
> ...
> I also didn't do anything about ExtensibleNode types. I assume just
> copying the ExtensibleNode isn't good enough. To flat copy the actual
> node I think would require adding a new function to
> ExtensibleNodeMethods.
Yeah, the problem I've got with this approach is that flat-copying
FDW and Custom paths would require extending the respective APIs.
While that's a perfectly reasonable ask if we only need to do this
in HEAD, it would be a nonstarter for released branches. Is it
okay to only fix this issue in HEAD?
> I was also unsure what we should do when shallow copying a List.
The proposal is to shallow-copy a Path node. List is not a kind
of Path, so how does List get into it? (Lists below Paths would
not get copied, by definition.)
regards, tom lane
