On 2011-12-20 18:44, Simon Riggs wrote:
> On Mon, Dec 19, 2011 at 11:10 AM, Simon Riggs<simon@2ndquadrant.com> wrote:
>
>> The only sensible way to handle this is to change the page format as
>> discussed. IMHO the only sensible way that can happen is if we also
>> support an online upgrade feature. I will take on the online upgrade
>> feature if others work on the page format issues, but none of this is
>> possible for 9.2, ISTM.
> I've had another look at this just to make sure.
>
> Doing this for 9.2 will change the page format, causing every user to
> do an unload/reload, with no provided mechanism to do that, whether or
> not they use this feature.
How about only calculating the checksum and setting it in the "bgwriter"
just before
flying the buffer off to disk.
Perhaps even let autovacuum do the same if it flushes pages to disk as a
part
of the process.
If someone comes along and sets a hint bit,changes data, etc. its only
job is to clear
the checksum to a meaning telling "we dont have a checksum for this page".
Unless the bgwriter becomes bottlenecked by doing it, the impact on
"foreground"
work should be fairly limited.
Jesper .. just throwing in random thoughts ..
--
Jesper
