> You need more parentheses -- (source::text) would've worked.
Alas, no, same problem as for CAST():
ERROR: functions in index expression must be marked IMMUTABLE
>> No problem, I can use CAST(), right? So I try: >> EXCLUDE USING gist (CAST(source AS text) WITH =, within WITH &&) >> Not so much: >> try.sql:13: ERROR: functions in index expression must be marked IMMUTABLE >> I guess it's because locale settings might change, and therefore change the text representation? Seems unlikely, though. > > Not locale, just renaming one of the values would be enough to break that. > Admittedly we don't provide an official way to do that ATM, but you can do > an UPDATE on pg_enum.
Ah, right. Maybe if there was a way to get at some immutable numeric value…
It seems reasonable to me to cast enum to oid. However, creating casts without function isn't allowed for enums.
test=# create cast (source as oid) without function;
ERROR: enum data types are not binary-compatible
However, this restriction can be avoided either by writing dummy C-function or touching catalog directly:
test=# insert into pg_cast values ((select oid from pg_type where typname = 'source'), (select oid from pg_type where typname = 'oid'), 0, 'e', 'b');
INSERT 341001 1
Then you can define desired restriction.
CREATE TABLE things (
source source NOT NULL,
within tstzrange NOT NULL,
EXCLUDE USING gist ((source::oid) WITH =, within WITH &&)
);
Probably, I'm missing something and casting enum to oid is somehow unsafe?
