Re: Freeze avoidance of very large table.

On Thu, Apr 23, 2015 at 10:42:59AM +0300, Heikki Linnakangas wrote:
> On 04/22/2015 09:24 PM, Robert Haas wrote:
> >>I would feel safer if we added a completely new "epoch" counter to the page
> >>>header, instead of reusing LSNs. But as we all know, changing the page
> >>>format is a problem for in-place upgrade, and takes some space too.
> >Yeah.  We have a serious need to reduce the size of our on-disk
> >format.  On a TPC-C-like workload Jan Wieck recently tested, our data
> >set was 34% larger than another database at the beginning of the test,
> >and 80% larger by the end of the test.  And we did twice the disk
> >writes.  See "The Elephants in the Room.pdf" at
> >https://sites.google.com/site/robertmhaas/presentations
> 
> Meh. Adding an 8-byte header to every 8k block would add 0.1% to the
> disk size. No doubt it would be nice to reduce our disk footprint,
> but the page header is not the elephant in the room.

Agreed.  Are you saying we can't find a way to fit an 8-byte value into
the existing page in a backward-compatible way?

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + Everyone has their own god. +