Re: Partial aggregates pushdown

On Thu, Oct 26, 2023 at 11:11:09AM +0000, Fujii.Yuki@df.MitsubishiElectric.co.jp wrote:
> >        and checks if the remote server version is older than the local server version.
> >        If so,
> >        <filename>postgres_fdw</filename>
> > -->       assumes that for each built-in aggregate function, the partial aggregate function is not defined
> > -->       on the remote server unless the partial aggregate function and the aggregate
> > -->       function match.
> >        Otherwise <filename>postgres_fdw</filename> assumes that for each built-in aggregate function,
> >        the partial aggregate function is defined on the remote server.
> >        The default is <literal>false</literal>.
> >       </para>
> >      </listitem>
> >     </varlistentry>
> > 
> > What does that marked sentence mean?  What is match?  Are one or both of these remote?  It sounds like you are
> > checking the local aggregate against the remote partial aggregate, but I don't see any code that does this in the
patch.
> This sentence means that
> "If the partial aggregate function has the same OID as the aggregate function,
> then postgres_fdw assumes that for each built-in aggregate function, the partial aggregate function is not defined
>  on the remote server."
> "Match" means that the partial aggregate function has the same OID as the aggregate function in local server.
> But, in v30, there is no code which checks the partial aggregate function has the same OID as the aggregate function
inlocal server.
 
> So I modified the code of is_builtin_aggpartialfunc_shippable().
> Also, I modified wording postgres-fdw.sgml.

Yes, that is what I needed.  Attached is a modification of your v31
patch (the most recent) that mostly improves the documentation and
comments.  What else needs to be done before committers start to review
this?

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

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