Обсуждение: AW: Re: Backup and Recovery

> > In other words, we keep the page images and row records in one file so
> > we can do one fsync, but once we have written the page, we don't want to
> > store them for later point-in-time recovery.
> 
> What we'd want to do is strip the page images from the version of the
> logs that's archived for recovery purposes.  Ideally the archiving
> process would also discard records from aborted transactions, but I'm
> not sure how hard that'd be to do.

Unless we have UNDO we also need to roll forward the physical changes of 
aborted transactions, or later redo records will "sit on a wrong physical image".

Andreas

Zeugswetter Andreas SB <ZeugswetterA@wien.spardat.at> writes:
>> Ideally the archiving
>> process would also discard records from aborted transactions, but I'm
>> not sure how hard that'd be to do.

> Unless we have UNDO we also need to roll forward the physical changes of 
> aborted transactions, or later redo records will "sit on a wrong physical image".

Wouldn't it be the same as the case where we *do* have UNDO?  How is a
removed tuple different from a tuple that was never there?
        regards, tom lane