On Sun, Feb 5, 2012 at 10:23 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Simon Riggs <simon@2ndQuadrant.com> writes:
>> Please post the patch rather than fixing directly. There's some subtle
>> stuff there and it would be best to discuss first.
>
> Here's a proposed patch for the issues around unlocked updates of
> shared-memory state. After going through this I believe that there is
> little risk of any real problems in the current state of the code; this
> is more in the nature of future-proofing against foreseeable changes.
> (One such is that we'd discussed fixing the age() function to work
> during Hot Standby.) So I suggest applying this to HEAD but not
> back-patching.
All looks very good to me. Agreed.
> Except for one thing. I realized while looking at the NEXTOID replay
> code that it is completely broken: it only advances
> ShmemVariableCache->nextOid when that's less than the value in the WAL
> record. So that comparison fails if the OID counter wraps around during
> replay. I've fixed this in the attached patch by just forcibly
> assigning the new value instead of trying to be smart, and I think
> probably that aspect of it needs to be back-patched.
Ouch! Well spotted.
Suggest fixing that as a separate patch; looks like backpatch to 8.0.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
