On 12 Apr 2014 08:35, "Jan Wieck" <j...@wi3ck.info> wrote: > > On 04/12/14 03:27, Heikki Linnakangas wrote: >> >> On 04/12/2014 12:07 AM, Jan Wieck wrote: >>> >>> Hackers,
>> Hmm. Do we snapshots to be stored in tables, and included in a dump? I >> don't think we can guarantee that will work, at least not across >> versions, as the way we handle snapshot internally can change. > > > At least Londiste and Slony do store snapshots as well as xids in tables and assuming that the txid epoch is properly bumped, that information is useful and valid after a restore. As I understand it the epoch increments whenever the xid wraps. A physical restore would continue the same xid space in the same epoch which should work fine as long as no system stores any txids outside the database from the "future". A pg_restore would start a new xid space from FirstNormalXid which would obviously not work with any stored txids.
