hello, thanks for replies, Adrian, Steven.
>So calling it can advance the xid manually. Some testing here showed >that what xmin or xmax is created depends on when you call txid_current >in either the original session or the concurrent sessions. I understand this and I am executing my statements inside a Transaction block so the xid is not incremented when calling it. >Also worth noting that an UPDATE in Postgres is a DELETE/INSERT process. >The clue is the ctid value. In Session 2 you are looking at the >original row(ctid=(0, 2) which has been marked as deleted(non-zero >xmax). In Session 3 you are looking at the new row(ctid(0, 4)). Yes. But why (ctid(0,4)) in *Session 3* carries the xmax of the txid 519115 in which the update failed with *UPDATE 0* . This is where I can not understand, 1. Row (0,4) is updated with correct value and (0,3) is not visible in Session 2, which is good. 2. but in *Session 3* (0,4) also carries xmax which means what? Is it also marked for deletion? It can't be, right? ----- -- Thanks, Rajan. -- View this message in context: http://www.postgresql-archive.org/Re-have-trouble-understanding-xmin-and-xmax-with-update-operations-from-two-different-sessions-tp5969644p5969656.html Sent from the PostgreSQL - general mailing list archive at Nabble.com. -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
