Re: Summary and Plan for Hot Standby

On Fri, Nov 20, 2009 at 7:31 AM, Heikki Linnakangas
<heikki.linnakangas@enterprisedb.com> wrote:
> Simon Riggs wrote:
>> On Fri, 2009-11-20 at 06:47 +0000, Greg Stark wrote:
>>> I missed the original discussion of this problem, do you happen to
>>> remember the subject or url for the details?
>>
>> December 2008; hackers; you, me and Heikki.
>
> Yep:
> http://archives.postgresql.org/message-id/494B5FFE.4090909@enterprisedb.com

And I can see I failed to understand the issue at the time.

From the list it looks like the last word was Simon's:
http://archives.postgresql.org/message-id/1229710177.4793.567.camel@ebony.2ndQuadrant

From discussions in the bar it sounds like this was actually a false
start however as the RecentGlobalXmin in the backend doing the split
could be less aggressive than the RecentGlobalXmin used by some other
backend to hit the hint bits leading to inconsistent results :(

I'm leaning towards having the backend actually go fetch all the
xmin/xmaxes of the pointers being pruned. It ought to be possible to
skip that check in any database with no live snapshots so recovery
performance would be unaffected on replicas not actively being used in
hot mode.

-- 
greg