> On Jun 28, 2022, at 23:42, Laurenz Albe <laurenz.albe@xxxxxxxxxxx> wrote: > That is not enough in the general case. You are not allowed to redefine > an IMMUTABLE function in a way that changes its behavior [...] I think "not allowed" is putting it too strongly. It would be a bit much to ask that every single user-written immutable function be 100% perfect when it is rolled out, and never have to fix any bugs in them. However, you definitely *do* have to understand that there are administrative consequences for doing so, like rebuilding indexes and invalidating session caches. I think that the OP's statement that you can't ever use user-defined functions from an immutable function is too strong, too; you need to be aware of the consequences if you change an immutable function in a way that alters the return result for a previously-valid set of arguments.
