Re: User's responsibility when using a chain of "immutable" functions?

[Christophe Pettus]

> On Jun 28, 2022, at 23:42, Laurenz Albe <laurenz.a...@cybertec.at> 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.