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From: Alexander Pyhalov <[email protected]>
To: [email protected] <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Cc: Bruce Momjian <[email protected]>
Cc: Finnerty, Jim <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: Tomas Vondra <[email protected]>
Cc: Julien Rouhaud <[email protected]>
Cc: Daniel Gustafsson <[email protected]>
Subject: Re: Partial aggregates pushdown
Date: Thu, 28 Sep 2023 09:15:43 +0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <OS3PR01MB6660E61EB659850022B9607195C1A@OS3PR01MB6660.jpnprd01.prod.outlook.com>
References: <[email protected]>
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[email protected] 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






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