-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 10/14/06 14:35, Michael Fuhr wrote: > On Sat, Oct 14, 2006 at 11:35:12AM -0700, Joshua D. Drake wrote: >> What is the use case for a READ ONLY transaction? > > I use read-only transactions as a safety net for interactive sessions > when I want to avoid modifying anything accidentally. Here's an > example: > > CREATE ROLE foo LOGIN PASSWORD 'password'; > CREATE ROLE foo_ro LOGIN PASSWORD 'password'; > ALTER ROLE foo_ro SET default_transaction_read_only TO on; > GRANT foo TO foo_ro; > > The foo_ro role now has the same privileges as foo but it can't > modify anything because its transactions are read-only by default. Another benefit (with ISOLATION LEVEL SERIALIZABLE) is that you are guaranteed to have unchanging source data, no matter how many ways you aggregate, join and WHERE it. As Tom notes, other RDBMSs do pre-query optimizations. SET TRANS READ ONLY tells the engine that these statements won't have to take out concurrent write locks, and can thus take a different, faster code path. - -- Ron Johnson, Jr. Jefferson LA USA Is "common sense" really valid? For example, it is "common sense" to white-power racists that whites are superior to blacks, and that those with brown skins are mud people. However, that "common sense" is obviously wrong. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (GNU/Linux) iD8DBQFFMUbHS9HxQb37XmcRAu1FAJ9jBwddmyS5V0IQgbeZYS8Jv85W/wCgpeAf j3jNyYxx7RWT74ed5YrfNLA= =rLJe -----END PGP SIGNATURE-----
