Craig Ringer <craig@xxxxxxxxxxxxxxx> writes: > I was looking through the latest spec drafts I have access to and > couldn't find any reference to Pg's optimisation-fence-for-CTEs > behaviour being required by the standard, though I've repeatedly seen it > said that there is such a requirement. I don't believe it's required by the standard (it's hard to see how it could be, when query optimization is a topic outside the spec to start with). However, we allow INSERT/UPDATE/DELETE RETURNING inside WITH, and for those I think you really need to treat WITH as an optimization fence. It's a lot more debatable for SELECT; there are some advantages to providing a fence this way but there are definitely downsides too. I could see adjusting that definition in the future, as we get more experience with use of CTEs. regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
