Re: pg_upgrade: How to deal with toast

Tom Lane napsal(a):
> Zdenek Kotala <Zdenek.Kotala@Sun.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