On 02/26/2017 07:56 AM, Geoff Winkless wrote: > On 26 February 2017 at 10:09, Sven R. Kunze <srkunze@mail.de > <mailto:srkunze@mail.de>>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.
