Re: Confusing docs about GetForeignUpperPaths in fdwhandler.sgml

From: Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Confusing docs about GetForeignUpperPaths in fdwhandler.sgml
Date: 2016-08-31 09:01:41
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On 2016/08/01 21:14, Etsuro Fujita wrote:
> I noticed that the following note about direct modification via
> GetForeignUpperPaths in fdwhandler.sgml is a bit confusing. We have
> another approach using PlanDirectModify, so that should be reflected in
> the note as well. Please find attached a patch.
> <function>PlanForeignModify</> and the other callbacks described in
> <xref linkend="fdw-callbacks-update"> are designed around the
> assumption
> that the foreign relation will be scanned in the usual way and then
> individual row updates will be driven by a local
> <literal>ModifyTable</>
> plan node. This approach is necessary for the general case where an
> update requires reading local tables as well as foreign tables.
> However, if the operation could be executed entirely by the foreign
> server, the FDW could generate a path representing that and insert it
> into the <literal>UPPERREL_FINAL</> upper relation, where it would
> compete against the <literal>ModifyTable</> approach.

I'll add this to the upcoming CF.

Best regards,
Etsuro Fujita

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