AW: WAL does not recover gracefully from out-of-disk-sp ace

> Regardless of whether this particular behavior is fixable, this brings
> up something that I think we *must* do before 7.1 release: create a
> utility that blows away a corrupted logfile to allow the system to
> restart with whatever is in the datafiles.  Otherwise, there is no
> recovery technique for WAL restart failures, short of initdb and
> restore from last backup.  I'd rather be able to get at data of
> questionable up-to-dateness than not have any chance of recovery
> at all.

It would imho be great if this utility would also have a means to 
extend a logfile, that was not extended to the full 16Mb, and
revert the change that writes the whole file in the init phase.

Imho this write at logfile init time adds a substantial amount of IO,
that would better be avoided. If we really need this, it would imho 
be better to preallocate N logfiles and reuse them after checkpoint.

Andreas