Re: Rollback using WAL files?

On Jan 26, 9:45 am, t(dot)(dot)(dot)(at)sss(dot)pgh(dot)pa(dot)us (Tom Lane) wrote:
> Florian Weimer <fwei(dot)(dot)(dot)(at)bfk(dot)de> writes:
> > In theory, this should be possible (especially if you haven't switched
> > off full page writes).Not really --- the WAL records are not designed to carry full
> information about the preceding state of the page, so you can't use them
> to undo. (Example: a DELETE record says which tuple was deleted, but
> not what was in it.)

It would be really useful if one had the option of allowing the WAL
records to keep track of what was in a tuple as evidenced here. I use
triggers on every production table to record every change to log tables
(which have rules to prevent deleting and updating). Allowing the
option of having the WAL do this seems like a good idea...

regards,
karen