Re: Plans for solving the VACUUM problem

> Another thought: do we need WAL UNDO at all to implement savepoints?
> Is there some way we could do them like nested transactions, wherein
> each savepoint-to-savepoint segment is given its own transaction number?
> Committing multiple xact IDs at once might be a little tricky, but it
> seems like a narrow, soluble problem.  Implementing UNDO without
> creating lots of performance issues looks a lot harder.

I am confused why we can't implement subtransactions as part of our
command counter?  The counter is already 4 bytes long.  Couldn't we
rollback to counter number X-10?

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