Thank you, Merlin Moncure.
On Mon, Jun 10, 2013 at 10:13 AM, Merlin Moncure <mmonc...@gmail.com> wrote: > On Sun, Jun 9, 2013 at 10:59 AM, Gustavo Amarilla Santacruz > <gusama...@gmail.com> wrote: > > Hello, all. > > > > In the PostgreSQL documentation I found "currval: Return the value most > > recently obtained by nextval for this sequence in the current session > ...." > > > > In other documentations (pgpool, for example), I found "Connection > Pooling > > pgpool-II saves connections to the PostgreSQL servers, and reuse them > > whenever a new connection with the same properties (i.e. username, > database, > > protocol version) comes in. It reduces connection overhead, and improves > > system's overall throughput" > > > > Then, I have the following question: PostgreSQL differentiates between > > sessions created for the same user? > > Connection pooling means you have to carefully consider using feature > of the database that is scoped to the session. This includes > currval(), prepared statements, listen/notify, advisory locks, 3rd > party libraries that utilize backend private memory, etc. > > For currval(), one solution is to only use those features > 'in-transaction', and make sure your pooler is fully transaction aware > -- pgbouncer does this and I think (but I'm not sure) that pgpool does > as well. > > Another solution is to stop using currval() and cache the value on the > client side. postgres 8.2 RETURNING facilities this: > > INSERT INTO foo (...) RETURNING foo_id; > > This is a better way to deal with basis CRUD -- it also works for all > default values, not just sequences. The only time I use currval() etc > any more is inside server side functions. > > merlin > -- ------------------------ Gustavo Amarilla
