On 2013-07-20 00:49:11 +0900, Hiroshi Inoue wrote: > (2013/07/18 21:46), Robert Haas wrote: > >There seems to be a consensus that we should try to get rid of > >SnapshotNow entirely now that we have MVCC catalog scans, so I'm > >attaching two patches that together come close to achieving that goal: > > ... > > >With that done, the only remaining uses of SnapshotNow in our code > >base will be in currtid_byreloid() and currtid_byrelname(). So far no > >one on this list has been able to understand clearly what the purpose > >of those functions is, so I'm copying this email to pgsql-odbc in case > >someone there can provide more insight. If I were a betting man, I'd > >bet that they are used in contexts where the difference between > >SnapshotNow and SnapshotSelf wouldn't matter there, either. > > Using SnapshotSelf instead of SnapshotNow for currtid_ () wouldn't > matter.
I think it actually might. You could get into dicey situations if you use currtid_ in a query performing updates or inserts because it would see the to-be-inserted tuple... Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
