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Re: [HACKERS] Performance testing of COPY (SELECT) TO

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Zoltan Boszormenyi <zboszor(at)dunaweb(dot)hu>
Cc: Andrew Dunstan <andrew(at)dunslane(dot)net>, Bruce Momjian <bruce(at)momjian(dot)us>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-patches(at)postgresql(dot)org
Subject: Re: [HACKERS] Performance testing of COPY (SELECT) TO
Date: 2006-08-28 17:00:13
Message-ID: 20060828170013.GS27526@alvh.no-ip.org (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
Zoltan Boszormenyi wrote:
> Alvaro Herrera írta:

> But COPY view (col1, col2, ...) TO may still be
> useful even if the COPY (SELECT ...) (col1, col2, ...) TO
> is pointless. [1]

Hum, I don't understand what you're saying here -- are you saying that
you can't do something with the first form, that you cannot do with the
second?


> >It's ugly because you are forcing the system to parse something that
> >was already parsed.
> 
> Well, to be true to the word, during parsing COPY view TO
> the parser never saw SELECT * FROM view.

Hmm!

The COPY view stuff stopped working when I changed back the "relation"
case.  Your patch changed it so that instead of flowing as RangeVar all
the way to the copy.c code, the parser changed it into a "select * from
%s" query, and then stashed the resulting Query node into the "query"
%case.  (So what was happening was that the Relation case was never
%used).  I reverted this.


> >On the other hand I don't see why you are arguing in favor of a useless
> >feature whose coding is dubious; you can have _the same thing_ with nice
> >code and no discussion.
> 
> Because of [1] and because Mr. Schoenig's arguments
> about changing schemas.

Yeah, that argument makes sense to me as well.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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