Re: Page-level version upgrade (was: Block-level CRC checks)

Robert Haas wrote:
> On Tue, Dec 1, 2009 at 5:15 PM, Greg Stark <gsstark@mit.edu> wrote:
> > On Tue, Dec 1, 2009 at 9:58 PM, decibel <decibel@decibel.org> wrote:
> >> What happened to the work that was being done to allow a page to be upgraded
> >> on the fly when it was read in from disk?
> >
> > There were no page level changes between 8.3 and 8.4.
> 
> That's true, but I don't think it's the full and complete answer to
> the question.  Zdenek submitted a page for CF 2008-11 which attempted
> to add support for multiple page versions.  I guess we're on v4 right
> now, and he was attempting to add support for v3 pages, which would
> have allowed reading in pages from old PG versions.  To put it
> bluntly, the code wasn't anything I would have wanted to deploy, but
> the reason why Zdenek gave up on fixing it was because several
> community members considerably senior to myself provided negative
> feedback on the concept.

Well, there were quite a number of open issues relating to page
conversion:
o  Do we write the old version or just convert on read?o  How do we write pages that get larger on conversion to the
newformat?
 

As I rember the patch allowed read/wite of old versions, which greatly
increased its code impact.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +