Re: Bug in autovacuum.c?

On Fri, Apr 1, 2011 at 11:18 AM, Bruce Momjian <bruce@momjian.us> wrote:
> Robert Haas wrote:
>> Oh, quite right.  Sorry I missed that.  I suppose if we wanted to fix
>> this for real, we'd want to get:
>>
>> 105->5
>> 104->4
>> 103->3
>> 102->max_xid
>> 101->max_xid-1
>> 100->max_xid-2
>> 99->max_xid-3
>> 98->max_xid-4
>>
>> But it doesn't seem worth getting excited about.
>
> I think (?) the problem with that is the every time you wrap around you
> get more out of sync.  :-O

It's not clear to me that it matters a bit, though.

> Thinking more, the problem is that when the xid counter wraps around
> from max_xid to 3, we jump the freeze horizon by three, e.g 5000 to
> 5003.  So when, the freeze horizon wraps, we can either have that jump
> by three, e.g set it to FirstNormalTransactionId, or delay by three,
> e.g. set it to MaxTransactionId.

So what?  :-)

--
Robert Haas
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