AW: AW: [HACKERS] ALTER TABLE DROP COLUMN

[Zeugswetter Andreas SB]

> > My conclusion would be that we need both:
> > 1. a fast system table only solution with physical/logical column id
> > 2. a tool that does the cleanup (e.g. vacuum) 
> 
> But the peak space usage during cleanup must still be 2X.

The difference for a cleanup would be, that it does not need to 
be rolled back as a whole (like current vacuum).
A cleanup could be partly done, and resumed later, thus a sofisticated 
cleanup could avoid 2X.

Andreas