Hannu Krosing wrote:
>
> Tom Lane wrote:
> >
> >> ALTER ADD COLUMN doesn't touch any tuples, and you're right that it's
> > critically dependent on heap_getattr returning NULL when an attribute
> > beyond the number of attributes actually present in a tuple is accessed.
> > That's a fragile and unclean implementation IMHO --- see past traffic
> > on this list.
>
> Short of redesigning the whole storage format I can see no better way to
> allow
> ALTER ADD COLUMN in any reasonable time. And I cna see no place where
> this is
> more "fragile and unclean implementation" than any other in postgres --
> OTOH it is quite hard for me to "see the past traffic on this list" as
> my
> "PgSQL HACKERS" mail folder is too big for anything else then grep ;)
>
I don't remember the traffic either.
IIRC,I objected to Tom at this point in pgsql-bugs recently.
I think it's very important for dbms that ALTER ADD COLUMN
touches tuples as less as possible.
Regards.
Hiroshi Inoue