Re: 16-bit page checksums for 9.2

On 29.02.2012 19:54, Simon Riggs wrote:
> I'm beginning to lose faith that objections are being raised at a
> rational level. It's not a panel game with points for clever answers,
> its an engineering debate about how to add features real users want.
> And they do want, so let me solve the problems by agreeing something
> early enough to allow it to be implemented, rather than just
> discussing it until we run out of time.

I thought my view on how this should be done was already clear, but just
in case it isn't, let me restate: Enlarge the page header to make room
for the checksum. To handle upgrades, put code in the backend to change
the page format from old version to new one on-the-fly, as pages are
read in. Because we're making the header larger, we need to ensure that
there's room on every page. To do that, write a utility that you run on
the cluster before running pg_upgrade, which moves tuples to ensure
that. To ensure that the space doesn't get used again before upgrading,
change the old version so that it reserves those N bytes in all new
insertions and updates (I believe that approach has been discussed
before and everyone is comfortable with backpatching such a change). All
of this in 9.3.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com