From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jan Wieck <JanWieck(at)Yahoo(dot)com>, btober(at)seaworthysys(dot)com, scrawford(at)pinpointresearch(dot)com, kleptog(at)svana(dot)org, m_tessier(at)sympatico(dot)ca, pgsql-general(at)postgresql(dot)org |
Subject: | Re: How many fields in a table are too many |
Date: | 2003-06-28 18:06:07 |
Message-ID: | 200306281806.h5SI67I08307@candle.pha.pa.us |
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Lists: | pgsql-general |
Alvaro Herrera wrote:
> On Sat, Jun 28, 2003 at 01:43:32PM -0400, Tom Lane wrote:
> > Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > > Is this a TODO?
> > > When columns can be reordered, move varlena columns to the end?
> >
> > I believe that really what you want is fixed-width NOT NULL columns
> > first, then fixed-width nullable, then var-width. This ordering will
> > improve the odds of actually being able to use the fixed offset for
> > a particular column.
>
> This means that when you do ALTER TABLE ... SET/DROP NOT NULL the table
> may have to be completely rewritten? Altering the physical order is
> sure to provoke a rewrite, but I think people will expect a change in
> constraints to be a fast operation.
I don't think we would change any physical ordering with ALTER TABLE ---
just do it when the table is created, if possible.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
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