On 03/04/2013 12:19 PM, Greg Smith wrote:
> On 3/3/13 10:52 PM, Craig Ringer wrote:
>> I also suspect that at least in the first release it might be desirable
>> to have an option that essentially says "something's gone horribly wrong
>> and we no longer want to check or write checksums, we want a
>> non-checksummed DB that can still read our data from before we turned
>> checksumming off".
>
> I see that as being something that involves disabling the cluster-wide
> flag that turns checksumming on, the one that is reported by
> pg_controldata. I think it would have to be a one-way, system down
> kind of change, which I think is fair given the ugly (but feasible)
> situation you're describing. It would need to be something stronger
> than a GUC. Once you start writing out pages without checksums, you're
> back into the fuzzy state where some pages have them, others don't,
> and there's no good way to deal with that yet.
Agreed, I was envisioning a one-way process where re-enabling checksums
would involve be a re-initdb and reload. A DB restart seems perfectly
reasonable, it's just a full dump and reload before they can get running
again that I feel must be avoided.
-- Craig Ringer http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services
