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

On 14 November 2012 16:20, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Alvaro Herrera <alvherre@2ndquadrant.com> writes:
>> Simon Riggs escribió:
>>> On 14 November 2012 15:09, Fujii Masao <masao.fujii@gmail.com> wrote:
>>>> Here, progname for COPY IN is the user-supplied program that takes filename as
>>>> its argument and that writes on standard output.
>
>>> I think we should be using FDWs/SRFs here, not inventing new
>>> syntax/architectures for executing external code, so -1 from me.
>
>> Hmm, but then you are forced to write C code, whereas the "external
>> program" proposal could have you writing a only shell script instead.
>
> 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.

Perhaps not cleaner, but we do need

COPY table FROM (SELECT * FROM foo)

So we will then have both ways.

-- Simon Riggs                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services