Re: BUG #18007: age(timestamp, timestamp) is marked as immutable, but using age(date, date) says it's not - Mailing list pgsql-bugs

> On Jun 29, 2023, at 11:29, Braiam <braiamp@gmail.com> wrote:
> Function age(timestamp with time zone, timestamp with time zone) is
> marked as immutable. Postgres shouldn't complain about it.

It's not the age() function as such that is the problem, but the (stable) cast from date to timestamptz.  Stable or
volatileinputs to an immutable function make the expression result non-immutable. 

For example, abs() is marked as immutable, but you can't do this:

xof=# CREATE TABLE t (i integer);
CREATE TABLE
xof=# CREATE INDEX ON t((abs(random()+i)));
ERROR:  functions in index expression must be marked IMMUTABLE