Re: Enabling Checksums

Bruce Momjian <bruce@momjian.us>

From: Bruce Momjian <bruce@momjian.us>

To: Tom Lane <tgl@sss.pgh.pa.us>

Cc: Greg Stark <stark@mit.edu>, Florian Pflug <fgp@phlo.org>, Ants Aasma <ants@cybertec.at>, Andres Freund <andres@2ndquadrant.com>, Jeff Davis <pgsql@j-davis.com>, Heikki Linnakangas <hlinnakangas@vmware.com>, Simon Riggs <simon@2ndquadrant.com>, Greg Smith <greg@2ndquadrant.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>

Date: 2013-04-17T18:10:17Z

Lists: pgsql-hackers

On Wed, Apr 17, 2013 at 01:29:18PM -0400, Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> > Uh, not sure how pg_upgrade would detect that as the version number is
> > not stored in pg_controldata, e.g.:
> 
> > 	Data page checksums:                  enabled/disabled
> 
> That seems pretty shortsighted.  The field probably ought to be defined
> as containing a checksum algorithm ID number, not a boolean.
> 
> But having said that, I'm not sure why this would be pg_upgrade's
> problem.  By definition, we do not want pg_upgrade running around
> looking at individual data pages.  Therefore, whatever we might do
> about checksum algorithm changes would have to be something that can be
> managed on-the-fly by the newer server.

Well, my idea was that pg_upgrade would allow upgrades from old clusters
with the same checksum algorithm version, but not non-matching ones. 
This would allow the checksum algorithm to be changed and force
pg_upgrade to fail.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +