Re: Partial aggregates pushdown

Fujii.Yuki@df.MitsubishiElectric.co.jp писал 2023-09-28 07:40:

>> I'm not sure that I like this mechanics of adding sort group clauses -
>> it seems we do in core additional work, which is of use only for
>> one extension, but at least it seems to be working.
> We cannot deparse the original sort group clauses and pathtarget
> when performing partial aggreggate pushdown by any FDWs.
> So I think the additional sort group clauses and pathtarget are
> needed by any FDWs, not only postgres_fdw.
> 

Hi.
It seems to me that *fdw postfixes don't clarify things, but just make 
naming more ugly.

+ * Adding these Vars and PlaceHolderVars to PathTarget,
+ * FDW cannot deparse this by the original List of SortGroupClauses.
+ * So, before this adding process,
+ * setGroupClausePartial generates another Pathtarget and another
+ * List of SortGroupClauses for FDW.

It seems that something like:

/*
  * Modified PathTarget cannot be used by FDW as-is to deparse this 
statement.
  * So, before modifying PathTarget, setGroupClausePartial generates
  * another Pathtarget and another list List of SortGroupClauses
  * to make deparsing possible.
  */

sounds better.

-- 
Best regards,
Alexander Pyhalov,
Postgres Professional