Re[4]: [GENERAL] Joins and links

Hello Bruce,

Tuesday, July 06, 1999 you wrote:

>>
>> Maybe it is a silly question, but what are "more than one version
>> of a record"? In my opinion record is a atomic unique entity.
>> Isn't it?

B> Read how MVCC works in the manuals.

Ah, you mean MVCC! That's what I replied to Tom Lane:

> This problem can be solved. An offhand solution is to have
> an additional system field which will point to new tuple left after
> update. It is filled at the same time as the original tuple is
> marked invalid.  So the scenario is as follows: we follow the link,
> and if we find that in the tuple where we arrived this system field
> is not NULL, we go to (the same table of course) where it is pointing
> to. Sure VACUUM will eliminate these. Performance penalty is small.

Best regards, Leon