(forgot to answer this question)
On 05/30/2014 06:27 PM, Andres Freund wrote:
> On 2014-05-30 17:59:23 +0300, Heikki Linnakangas wrote:
>> * I expanded pg_clog to 64-bits per XID, but people suggested keeping
>> pg_clog as is, with two bits per commit, and adding a new SLRU for the
>> commit LSNs beside it. Probably will need to do something like that to avoid
>> bloating the clog.
>
> It also influences how on-disk compatibility is dealt with. So: How are
> you planning to deal with on-disk compatibility?
Have pg_upgrade read the old clog and write it out in the new format.
- Heikki