Re: Enabling Checksums

On Mon, Nov 12, 2012 at 04:42:57PM -0800, Josh Berkus wrote:
> Jeff,
>
> > OK, so here's my proposal for a first patch (changes from Simon's
> > patch):
> >
> > * Add a flag to the postgres executable indicating that it should use
> > checksums on everything. This would only be valid if bootstrap mode is
> > also specified.
> > * Add a multi-state checksums flag in pg_control, that would have
> > three states: OFF, ENABLING, and ON. It would only be set to ON during
> > bootstrap, and in this first patch, it would not be possible to set
> > ENABLING.
> > * Remove GUC and use this checksums flag everywhere.
> > * Use the TLI field rather than the version field of the page header.
> > * Incorporate page number into checksum calculation (already done).
> >
> > Does this satisfy the requirements for a first step? Does it interfere
> > with potential future work?
>
> So the idea of this implementation is that checksums is something you
> set at initdb time, and if you want checksums on an existing database,
> it's a migration process (e.g. dump and reload)?
>
> I think that's valid as a first cut at this.

pg_upgrade will need to check for the checksum flag and throw an error
if it is present in the new cluster but not the old one.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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