> If "pre-page WAL write" means the value of the page before the current
> changes, then there is generally another reason for writing it out.

Bruce, "*pre*-page" is confusing - we write "after-change" page
image to WAL.

> When the system comes back up, we need to do a rollback on
> transaction B since it did not commit and we need the "pre-page"
> to know how to undo the change for B that got saved in step 6 above.

Brian, PGSQL still uses non-overwriting storage manager -
removing rows inserted by aborted transactions is not required.

Vadim

Thu, 20 Dec 2001 16:03:58 -0800
"Mikheev, Vadim" <vmikheev@SECTORBASE.COM>
Re: TOAST performance (was Re: [GENERAL] Delete Perform
> > If "pre-page WAL write" means the value of the page before the current
> > changes, then there is generally another reason for writing it out.
> 
> Bruce, "*pre*-page" is confusing - we write "after-change" page
> image to WAL.

Yes, I didn't like pre-page either.  Changed.


-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

Thu, 20 Dec 2001 22:56:06 -0500 (EST)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: TOAST performance (was Re: [GENERAL] Delete Perform