Re: Function scan FDW pushdown

Álvaro Herrera писал(а) 2025-08-05 22:55:

Hello,

On 2024-Nov-05, g.kashkin@postgrespro.ru wrote:

This is a long-overdue follow-up to the original patch.
Note that this patch contains only the changes required for
function scan pushdown, examples and code related to asymmetric
join are dropped.

I've marked this as returned with feedback, as several months have
passed without a further version; the current one has a number of
gotchas, including some problematic coding detected by a compiler
warning, as well as unfinished design:

The issue with setting newrte->functions to NIL still persists.
[...]
I am aware that the rte->functions will now be copied even on
instances that don't utilize a FDW, but I don't see a way to solve it.
Any suggestions are welcome.

Feel free to reopen this CF entry[1] once you're able to figure this
out.

[1] https://commitfest.postgresql.org/patch/5470/

Hi.
I've updated patch with latest fixes, including more checks for corner
cases.
Now function pushdown is forbidden for functions, returning sets of
complex types
or which arguments contain parameters. Together with Gleb Kashkin we've
also moved
information about functions to foreign scan private data. The tricky
part here was
to get correct rti mappings after setrefs, but it seems we've managed to
do it.
Also I've removed some changes, which are required only in presence of
asymmetric
join.

Of course, I'm targeting PostgreSQL 20.
--
Best regards,
Alexander Pyhalov,
Postgres Professional