Re: ALTER TABLE DROP COLUMN

Chris Bitmead <chris@bitmead.com> writes:
> I don't know if this is one of the 5, but my idea of a good
> implementation is to do the fast invisible approach, and then update
> individual tuples to the new format the next time they happen to be
> UPDATEd.

How would you tell whether a particular tuple has been updated or not?

Furthermore, how would you remember the old tuple format (or formats)
so that you'd know how to make the conversion?

Seems to me this approach would require adding some sort of table
version number to every tuple header, plus storing a complete set of
system catalog entries for every past version of each table's schema.
That's a heck of a high price, in both storage and complexity, for a
feature of dubious value...

			regards, tom lane