On 1/26/06, Eric B. Ridge <ebr@xxxxxxxx> wrote: > Outside of "VACUUM FREEZE", is there any way the "xmin" column in a > relation can change, assuming of course the tuple is never updated > again? I'm considering using this as a way to identify all tuples > modified in the same transaction (in an effort to group them > together), and am wondering if there's any way tuples from different > transactions could end up with the same xmin value. I had the same problem - how to identify rows by transaction. I solved it by using the xxid from Slony-I and making it 8-byte. http://gborg.postgresql.org/pipermail/slony1-general/2006-January/003668.html http://gborg.postgresql.org/pipermail/slony1-general/2006-January/003685.html It has only 2 slight gotchas: - the function will fail if there are more than 2G tx'es between calls - you need to bump epoch if you reload dump. otherwise seems to work fine. Btw it uses TopTransactionId, so subtransactions should not be problem. -- marko
