> If PostgreSQL wants to stay MVCC, then we should imho forget
> "overwriting smgr" very fast.
> 
> Let me try to list the pros and cons that I can think of:
> Pro:
> 	no index modification if key stays same
> 	no search for free space for update (if tuple still
>         fits into page)
> 	no pg_log
> Con:
> 	additional IO to write "before image" to rollback segment
> 		(every before image, not only first after checkpoint)
> 		(also before image of every index page that is updated !)

I don't think that Oracle writes entire page as before image - just
tuple data and some control info. As for additional IO - we'll do it
anyway to remove "before image" (deleted tuple data) from data files.

Vadim

Thu, 24 May 2001 10:30:39 -0700
"Mikheev, Vadim" <vmikheev@SECTORBASE.COM>
RE: Plans for solving the VACUUM problem