From: | The Hermit Hacker <scrappy(at)hub(dot)org> |
---|---|
To: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Hiroshi Inoue <Inoue(at)tpf(dot)co(dot)jp>, Peter Eisentraut <peter_e(at)gmx(dot)net>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: [HACKERS] Well, then you keep your darn columns |
Date: | 2000-01-25 01:34:48 |
Message-ID: | Pine.BSF.4.21.0001242133440.362-100000@thelab.hub.org |
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Lists: | pgsql-hackers |
On Mon, 24 Jan 2000, Bruce Momjian wrote:
> > > The only drawback of this scheme is that the space occupied by the
> > > deleted column wouldn't go away immediately (in any given tuple,
> > > it'd be reclaimed on the next UPDATE of the tuple). On the other hand,
> > > you could construe that as a feature --- you don't have to wait around
> > > for a DROP COLUMN to finish. Anyone who did want to reclaim space
> > > immediately could do
> > > UPDATE table SET someothercolumn = someothercolumn;
> > > followed by a VACUUM. But I bet a lot of people would be just as
> > > happy to let it happen in background.
> >
> > Hey Bruce ... Look here ^^^^ :)
> >
> > Oh, there is a second drawback to it though ...
> >
> > DROP COLUMN name
> > ADD COLUMN name <of a different type>
> >
> > Then what? :(
>
> Double-yikes. There goes that idea, or does it? Attributes are
not necessarily, just playing devil's advocate ... :)
> numbered. How does a missing attribute get handled for new rows?
> My guess is that we have to keep this thing around forever. Can you
> imagine having all those user apps tha query pg_attribute supress that
> column. Sound like too much work to me.
I *still* think the best is the "re-write the table in place" method
... we already have most of the logic, I would think, from VACUUM ...
Marc G. Fournier ICQ#7615664 IRC Nick: Scrappy
Systems Administrator @ hub.org
primary: scrappy(at)hub(dot)org secondary: scrappy(at){freebsd|postgresql}.org
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