On Thu, Dec 7, 2023 at 4:12 PM Bruce Momjian <bruce@momjian.us> wrote:
> Second, the patch already has a mechanism to check the remote server
> version to see if it is the same or newer. Here is the version check
> documentation patch:
Right. This feature can certainly be implemented in a
backward-compatible way. I'm not sure that we have as much control
over what does and does not get pushed down as we really want here,
but it's completely possible to do this in a way that doesn't break
other use cases.
> However, functions don't have pre-created records, and internal
> functions don't see to have an SQL-defined structure, but as I remember
> the internal aggregate functions all take the same internal structure,
> so I guess we only need one fixed input and one output that would
> output/input such records. Performance might be an issue, but at this
> point let's just implement this and measure the overhead since there are
> few/any(?) other viable options.
IMHO records will be the easiest approach, but it will be some work to try it.
> Fourth, going with #2 where we do the pushdown using an SQL keyword also
> allows extensions to automatically work, while requiring partial
> aggregate functions for every non-partial aggregate will require work
> for extensions, and potentially lead to more version mismatch issues.
Yeah.
> Finally, I am now concerned that this will not be able to be in PG 17,
> which I was hoping for.
Getting it ready to ship by March seems very difficult. I'm not saying
it couldn't happen, but I think more likely it won't.
--
Robert Haas
EDB: http://www.enterprisedb.com