On Tue, Jul 2, 2013 at 5:19 AM, 高健 <luckyjackgao@xxxxxxxxx> wrote: > Hello: > I looked into the source code, and I think I now understand it: > cmin and cmax are same! The documentation is too old now. Yes, you figured it out. For short: cmin and cmax are overlapped fields and are used within the same transaction to identify the command that changed a tuple, so that in-transaction commands can be ordered and, therefore, tuple visibility can be calculated. Luca -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
