Re: WIP patch: add (PRE|POST)PROCESSOR options to COPY

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>, Craig Ringer <ringerc(at)ringerc(dot)id(dot)au>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: WIP patch: add (PRE|POST)PROCESSOR options to COPY
Date: 2012-11-14 16:32:58
Message-ID: 50A3C7BA.7030000@dunslane.net
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On 11/14/2012 11:20 AM, Tom Lane wrote:
> I disagree with Simon's objection also, because neither reading from
> nor writing to an external program is likely to fit the model of
> reading/updating a table very well. For instance, there's no good
> reason to suppose that reading twice will give the same results. So
> force-fitting this usage into the FDW model is not going to work well.
>
> Nor do I really see the argument why a "pipe_fdw" module is cleaner
> than a "COPY TO/FROM pipe" feature.
>
>

Yeah, I agree, although the syntax looks a bit unclean.

Maybe something like

COPY foo FROM wherever WITH (FILTER '/path/to/program')

might work better. You'd hook up the source to the filter as its stdin
and read its stdout. Not sure what we'd do for \copy though.

cheers

andrew

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