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 16:36:30 |
Message-ID: | 20060828163630.GN27526@alvh.no-ip.org |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers pgsql-patches |
Zoltan Boszormenyi wrote:
> Alvaro Herrera írta:
> >Remember that we were talking about supporting views, not tables. And
> >if a view uses a slow query then you are in immediate danger of having a
> >slow COPY. This may not be a problem but it needs to be discussed and
> >an agreement must be reached before introducing such a change (and not
> >during feature freeze).
>
> COPY relname TO meant tables _and_ views to me.
> My previous tsting showed no difference between
> COPY table TO and COPY (SELECT * FROM table) TO.
> Similarly a slow query defined in the view should show
> no difference between COPY view TO and
> COPY (SELECT * FROM view) TO.
The difference is that we are giving a very clear distinction between a
table and a view. If we don't support the view in the direct COPY, but
instead insist that it be passed via a SELECT query, then the user will
be aware that it may be slow.
"relname" at this point may mean anything -- are you supporting
sequences and toast tables as well?
> And remember, Bruce put the original COPY view TO
> patch into the unapplied queue, without the SELECT
> feature.
All sort of junk enters that queue so that's not an argument. (Not
meant to insult Bruce -- I'm just saying that he doesn't filter stuff.
We've had patches rejected from the queue before plenty of times.)
> Rewriting COPY view TO internally to
> COPY (SELECT * FROM view) TO is very
> straightforward, even if you think it's ugly.
> BTW, why is it ugly if I call raw_parser()
> from under src/backend/parser/*.c ?
> It is on a query distinct to the query the parser
> is currently running. Or is it the recursion
> that bothers you? It's not a possible infinite
> recursion.
It's ugly because you are forcing the system to parse something that
was already parsed.
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.
--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
From | Date | Subject | |
---|---|---|---|
Next Message | Alvaro Herrera | 2006-08-28 16:44:08 | Re: [HACKERS] Performance testing of COPY (SELECT) TO |
Previous Message | Hans-Juergen Schoenig | 2006-08-28 16:26:52 | Re: [HACKERS] Performance testing of COPY (SELECT) TO |
From | Date | Subject | |
---|---|---|---|
Next Message | Alvaro Herrera | 2006-08-28 16:44:08 | Re: [HACKERS] Performance testing of COPY (SELECT) TO |
Previous Message | Hans-Juergen Schoenig | 2006-08-28 16:26:52 | Re: [HACKERS] Performance testing of COPY (SELECT) TO |