alter table drop column

I read the transcript of the alter table drop column discussion (old
discussion) at http://www.postgresql.org/docs/pgsql/doc/TODO.detail/drop,
and I have something to add:

People mentioned such ideas as a hidden column and a really deleted column,
and it occurred to me that perhaps "vacuum" would be a good option to use.
When a delete was issued, the column would be hidden (by a negative/invalid
logical column number, it appears was the consensus). Upon issuing a
vacuum, it could perform a complete deletion. This method would allow users
to know that the process may take a while (I think the agreed method for a
complete delete was to "select into..." the right columns and leave out the
deleted ones, then delete the old table).

Furthermore, I liked the idea of some kind of "undelete", as long as it was
just hidden. This could apply to anything that is cleaned out with a vacuum
(before it is cleaned out), although I am not sure how feasible this is,
and it isn't particularly important to me.

Regards,
Jeff

--
Jeff Davis
Dynamic Works
jdavis(at)dynworks(dot)com
http://dynworks.com