Re: CLUSTER and MVCC

Mike Rylander wrote:
> On 3/9/07, Florian G. Pflug <fgp@phlo.org> wrote:
>> Couldn't HOT in principle deal with this? Let's say you have two 
>> long-running
>> transactions, which see row versions A and D. While those transactions
>> are running, the row is constantly updated, leading to row versions B, 
>> C (before
>> the second long-running transaction started), D, E, F, ... Z.
>> Now, the versions B,C,E,F,...Z could be removed by HOT or vacuum, 
>> because they
>> are not currently visible, nor will they ever become visible because 
>> they are
>> already deleted.
> 
> Couldn't they (or at least one of them) become visible due to
> SAVEPOINT rollback?

You wouldn't remove tuples with an uncommited xmax, of course.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com