> > Anyway I like idea of StartUpID in page headers - this will help
>
> Can you please describe StartUpID for me ?
> Ideal would be a stamp that has the last (smallest open) XID, or something else
> that has more or less timestamp characteristics (without the actual need of wallclock)
> in regard to the WAL.
StartUpID counts database startups and so has timestamp characteristics.
Actually, idea is to use SUI in future to allow reusing XIDs after startup: seeing
old SUI in data pages we'll know that all transaction on this page was committed
"long ago" (ie visible from MVCC POV). This requires UNDO, of course.
> This could then also be used to scan all pages for modification since
> last backup, to make incremental backups possible. (note, that incremental
> backup is not WAL backup)
We can scan log itself to get all pages modified since last backup or whatever
point we want - thanks to your idea about data pages backup.
Vadim