Marsh Ray escribió: > On Mon, May 18, 2009 at 6:20 PM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > > Marsh Ray <marsh5143@xxxxxxxxx> writes: > >> The central question: So if I successfully commit an update > >> transaction on one connection, then instantaneously issue a select on > >> another previously-opened connection, under what circumstances am I > >> guaranteed that the select will see the effects of the update? > > > > If the select is using a snapshot taken later than the commit, it will > > see the effects of the update. > > Great! Just the kind of definitive answer I was looking for. > > Now I just need to find a comprehensive list of all the things that > could cause an older snapshot to be retained, and ensure that none of > them could possibly be occurring on this connection. On a serializable transaction all queries will use the same snapshot taken when the first query is executed. Otherwise (read committed), a new query always gets a fresh one. (Old snapshots are also used for stuff like cursors that remain open, but that's not the case here.) -- Alvaro Herrera http://www.CommandPrompt.com/ PostgreSQL Replication, Consulting, Custom Development, 24x7 support -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
