* Scott Marlowe: > On Thu, Jan 19, 2012 at 7:54 AM, Florian Weimer <fweimer@xxxxxx> wrote: >> * Gnanakumar: >> >>>> Just create a unique index on EMAIL column and handle error if it comes >>> >>> Thanks for your suggestion. Of course, I do understand that this could be >>> enforced/imposed at the database-level at any time. But I'm trying to find >>> out whether this could be solved at the application layer itself. Any >>> thoughts/ideas? >> >> If you use serializable transactions in PostgreSQL 9.1, you can >> implement such constraints in the application without additional >> locking. However, with concurrent writes and without an index, the rate >> of detected serialization violations and resulting transactions aborts >> will be high. > > No, you sadly can't. PostgreSQL doesn't yet support proper predicate > locking to allow the application to be sure that the OP's original > statement, and ones like it, don't have a race condition. A unique > index is the only way to be sure. Huh? This was one of the major new features in PostgreSQL 9.1. -- Florian Weimer <fweimer@xxxxxx> BFK edv-consulting GmbH http://www.bfk.de/ Kriegsstraße 100 tel: +49-721-96201-1 D-76133 Karlsruhe fax: +49-721-96201-99 -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
