Yeah, you've got the right idea. Specifically, functions that operate on TIMESTAMPTZ aren't typically marked as IMMUTABLE (because their output implicitly depen

Yeah, you've got the right idea. Specifically, functions that operate on TIMESTAMPTZ aren't typically marked as IMMUTABLE (because their output implicitly depends on the connection-level time zone setting), and that IMMUTABLE flag is required for functions used in indexed expressions. https://www.postgresql.org/docs/current/xfunc-volatility.html https://www.postgresql.org/docs/current/xfunc-volatility.htm...