Re: Checksums, state of play

On Tue, Mar 6, 2012 at 11:50 AM, Simon Riggs <simon@2ndquadrant.com> wrote:
> On Tue, Mar 6, 2012 at 4:06 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
>> On Tue, Mar 6, 2012 at 3:31 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
>>
>>> I'll keep an open mind for now about database/table level. I'm not
>>> sure how possible/desirable each is.
>>
>> Table level sounds great, but how will it work with recovery? We don't
>> have a relcache in Startup process.
>>
>> So either database or tablespace level seems doable.
>
> Even db or ts level is problematic.
>
> Options
>
> (1) Recovery ignores checksums until db in consistent state
>
> (2) Recovery ignores checksums until all databases are enabled, when
> we set flag in pg_control
>
> (3) Recovery checks blocks marked as having a checksum, no matter the
> overall state

How about combining #1 and #3?  If the database isn't consistent yet
(and thus we can't look at pg_database) then we rely on the blocks
themselves to tell us whether they have checksums.  Once we reach
consistency we can do better.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company