Thread

Re: Function scan FDW pushdown

Alexander Pyhalov <a.pyhalov@postgrespro.ru> — 2026-05-06T06:59:15Z

Alexander Pyhalov писал(а) 2026-03-18 15:08:
> 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.

Hi.  Updated patch to apply cleanly after recent changes.
-- 
Best regards,
Alexander Pyhalov,
Postgres Professional