OK, I'm kind of interested now in how the variable length attributes are
actually stored on disk, that you are able to increase them, but not
decrease?
I would have thought the other way around?
Chris
> -----Original Message-----
> From: Stephan Szabo [mailto:sszabo@megazone23.bigpanda.com]
> Sent: Friday, 7 December 2001 10:05 AM
> To: Christopher Kings-Lynne
> Cc: tinar; pgsql-sql@postgresql.org
> Subject: RE: [SQL] how to chane the type
>
>
>
> On Fri, 7 Dec 2001, Christopher Kings-Lynne wrote:
>
> > What's the essential problem with changing column types in
> postgres? Is it
> > similar to the DROP COLUMN problem?
> >
> > If the answer is that the table format only has allocated
> enough space per
> > row for the existing type, then how is it possible that
> Stephen's hack below
> > will not break things?
>
> The hack below only works to change the max length of variable length
> attributes and only upward. I'd be very wary of trying to change the real
> type of a value except between ones that are bitwise compatible (like I
> think varchar and text are technically, but I'm not sure).
>
> > > The best way is to recreate the table and rename
> > > them around. If you *REALLY* don't want to do
> > > that and have a recent backup (yes, I'm serious),
> > > you can muck with pg_attribute and change
> > > atttypmod for the attribute in question
> > > (from 14 to 34).
>
