Re: ALTER TABLE DROP COLUMN

On Mon, 9 Oct 2000, Bruce Momjian wrote:

> > On Mon, 9 Oct 2000, Bruce Momjian wrote:
> > 
> > > > The Hermit Hacker <scrappy@hub.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 :)  
> 
> You know this DROP COLUMN is a hot button for me.

Ya, but in one email, you appear to agree with me ... then Tom posts a
good point and you jump over to that side ... at least pick a side? :)  I
too wish to see it implemented, I just don't want to have to double my
disk space if at some point I decide to upgrade an application and find
out that they decided to change their schema(s) :(