It says here that CREATE CAST insists the cast function be immutable. This seems wrong to me, in view of the fact that we have numerous built-in casts that don't adhere to that rule --- for example, timestamptz(date) is not immutable because it depends on the timezone setting.
Perhaps there's a case for prohibiting volatile casts (as opposed to stable ones), but I don't really see it. I'd prefer to just remove this restriction. Comments? regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/users-lounge/docs/faq.html