Re: ALTER TABLE DROP COLUMN

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>, PostgreSQL Development <pgsql-hackers(at)postgreSQL(dot)org>
Subject: Re: ALTER TABLE DROP COLUMN
Date: 2000-10-09 23:38:30
Message-ID: Pine.BSF.4.21.0010092038030.625-100000@thelab.hub.org
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On Mon, 9 Oct 2000, Bruce Momjian wrote:

> > The Hermit Hacker <scrappy(at)hub(dot)org> writes:
> > > hrmm .. mvcc uses a timestamp, no? is there no way of using that
> > > timestamp to determine which columns have/haven't been cleaned up
> > > following a crash? maybe some way of marking a table as being in a 'drop
> > > column' mode, so that when it gets brought back up again, it is scan'd for
> > > any tuples older then that date?
> >
> > WAL would provide the framework to do something like that, but I still
> > say it'd be a bad idea. What you're describing is
> > irrevocable-once-it-starts DROP COLUMN; there is no way to roll it back.
> > We're trying to get rid of statements that act that way, not add more.
> >
> > I am not convinced that a 2x penalty for DROP COLUMN is such a huge
> > problem that we should give up all the normal safety features of SQL
> > in order to avoid it. Seems to me that DROP COLUMN is only a big issue
> > during DB development, when you're usually working with relatively small
> > amounts of test data anyway.
> >
>
> Bingo!

you are jumping on your 'I agree/Bingo' much much too fast :)

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