Re: pg_upgrade: How to deal with toast

Tom Lane napsal(a):
> Zdenek Kotala <Zdenek(dot)Kotala(at)Sun(dot)COM> writes:
>> Heikki Linnakangas napsal(a):
>>> Perhaps we should just add the new attid attribute to the toast table,
>>> but mark it as nullable?
>
>> Hmm, It seems to me as a good idea.
>
> No, it's a really horrid idea. Nullable attributes complicate the C
> code, and what in the world are we buying with it anyway? Just decide
> what the field should contain and put it in there.

The problem what we try to solve is to perform this change during upgrade from
8.3->8.4. Extra value is a problem because it requires extra space and there is
not free space. It is temporal solution(hack) for 8.3->8.4.

Another thing what we can do is to perform "fake" page conversion of heap which
will retoast a toasted value which are present on heap tuples. The toasted table
will contains two kind of tuples, but in normal situation only converted tuples
should be accessed.

Zdenek