Re: Foreign join pushdown vs EvalPlanQual

From: Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>
To: Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, 花田茂 <shigeru(dot)hanada(at)gmail(dot)com>
Subject: Re: Foreign join pushdown vs EvalPlanQual
Date: 2015-10-05 08:55:37
Message-ID: 56123B09.30906@lab.ntt.co.jp
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On 2015/09/29 16:36, Etsuro Fujita wrote:
> For the foreign table case (scanrelid>0), I imagined an approach
> different than yours. In that case, I thought the issue would be
> probably addressed by just modifying the remote query performed in
> RefetchForeignRow, which would be of the form "SELECT ctid, * FROM
> remote table WHERE ctid = $1", so that the modified query would be of
> the form "SELECT ctid, * FROM remote table WHERE ctid = $1 AND *remote
> quals*".

Sorry, I was wrong. I noticed that the modifieid query (that will be
sent to the remote server during postgresRefetchForeignRow) should be of
the form "SELECT * FROM (SELECT ctid, * FROM remote table WHERE ctid =
$1) ss WHERE *remote quals*". (I think the query of the form "SELECT
ctid, * FROM remote table WHERE ctid = $1 AND *remote quals*" would be
okay if using a TID scan on the remote side, though.)

Best regards,
Etsuro Fujita

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