On 02/26/2017 07:56 AM, Geoff Winkless wrote:
> On 26 February 2017 at 10:09, Sven R. Kunze <srkunze@xxxxxxx
> <mailto:srkunze@xxxxxxx>>wrote:
>
> >>># create index docs_birthdate_idx ON docs using btree
> (((meta->>'birthdate')::date));
> ERROR: functions in index _expression_ must be marked IMMUTABLE
>
> So, what is the problem here?
>
>
> Date functions are inherently not immutable because of timezones. Your
> solution of using to_timestamp doesn't help because it automatically
> returns a value in WITH TIMESTAMP. Do you get anywhere by using
> "::timestamp without time zone" instead, as suggested here?
Of course I meant "WITH TIMEZONE" here, finger slippage.
My attempts at working the OP's problem passed through that:
Apologies, I don't have that reply in the thread in my mailbox.
test=> create index docs_birthdate_idx ON docs using btree (((meta->>'birthdate')::timestamp));
ERROR: functions in index _expression_ must be marked IMMUTABLE
Isn't the point that casting to ::timestamp will still keep the timezone? Hence casting to "without timezone".
This works:
test=> create index docs_birthdate_idx ON docs using btree ((meta->>'birthdate'));
CREATE INDEX
It is the act of casting that fails. Other then the OP's own suggestion of creating
a function that wraps the operation and marks it immutable I don't have a solution at
this time
I can imagine that without a cast, depending on the way birthdate is stored, it may behave differently to a cast index for ordering.
Geoff
