AW: Vacuum only with 20% old tuples

> >> We can't "drop and recreate" without a solution to the relation
> >> versioning issue (unless you are prepared to accept a nonfunctional
> >> database after a failure partway through index rebuild on a system
> >> table).  I think we should do this, but it's not all that simple...
> 
> > Is this topic independent of WAL in the first place ?
> 
> Sure, unless Vadim sees some clever way of using WAL to eliminate
> the need for versioned relations.  But as far as I've seen in the
> discussions, versioned relations are independent of WAL.

WAL can solve the versioned relations problem.
Remember that a sure new step in postmaster startup will be a rollforward of
the WAL,
since that will have the only sync write of our last txn's. Thus in this
step it can also 
do any pending rename or delete of files. If a rename or delete fails we 
bail out, since we don't want postmaster running under such circumstances
anyway.

Andreas