Re: Plans for solving the VACUUM problem

On Fri, May 18, 2001 at 06:10:10PM -0700, Mikheev, Vadim wrote:
> > Vadim, can you remind me what UNDO is used for?
> 
> Ok, last reminder -:))
> 
> On transaction abort, read WAL records and undo (rollback)
> changes made in storage. Would allow:
> 
> 1. Reclaim space allocated by aborted transactions.
> 2. Implement SAVEPOINTs.
>    Just to remind -:) - in the event of error discovered by server
>    - duplicate key, deadlock, command mistyping, etc, - transaction
>    will be rolled back to the nearest implicit savepoint setted
>    just before query execution; - or transaction can be aborted by
>    ROLLBACK TO <savepoint_name> command to some explicit savepoint
>    setted by user. Transaction rolled back to savepoint may be continued.
> 3. Reuse transaction IDs on postmaster restart.
> 4. Split pg_log into small files with ability to remove old ones (which
>    do not hold statuses for any running transactions).

I missed the original discussions; apologies if this has already been
beaten into the ground.  But... mightn't sub-transactions be a 
better-structured way to expose this service?

Nathan Myers
ncm@zembu.com