Re: Odd system-column handling in postgres_fdw join pushdown patch

From: Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>
To: Robert Haas <robertmhaas(at)gmail(dot)com>, Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>
Cc: "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Odd system-column handling in postgres_fdw join pushdown patch
Date: 2016-04-14 03:21:47
Message-ID: 570F0CCB.50008@lab.ntt.co.jp
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On 2016/04/14 12:04, Etsuro Fujita wrote:
> On 2016/04/14 4:57, Robert Haas wrote:
>> 2. When a join is pushed down, deparse system columns using something
>> like "CASE WHEN r1.* IS NOT NULL THEN 0 END", except for the table OID
>> column, which gets deparsed with the table OID in place of 0. This
>> delivers the correct behavior in the presence of outer joins.

> I think that that would cause useless data transfer for such culumns.
> Why not set values locally for such columns?

At least for the table OID.

Best regards,
Etsuro Fujita

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