Обсуждение: Creating an index on a timestamp with time zone cast to a date-- possible?

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Creating an index on a timestamp with time zone cast to a date-- possible?

От
Wells Oliver
Дата:
Seems you can't do this:

create index on someschema.sometable ((modified_at::date));

If modified_at is a timestamp with a time zone:

ERROR:  functions in index expression must be marked IMMUTABLE

But you can if it's a timestamp without a time zone. Anyway, any way of casting that as to use it as an index?

--

Re: Creating an index on a timestamp with time zone cast to a date-- possible?

От
Tom Lane
Дата:
Wells Oliver <wells.oliver@gmail.com> writes:
> Seems you can't do this:
> create index on someschema.sometable ((modified_at::date));
> If modified_at is a timestamp with a time zone:
> ERROR:  functions in index expression must be marked IMMUTABLE
> But you can if it's a timestamp without a time zone. Anyway, any way of
> casting that as to use it as an index?

The problem is that casting a timestamptz to a date (or a timestamp
for that matter) depends on your current timezone setting.

You could do something like

create index on sometable (((modified_at at time zone 'UTC')::date));

            regards, tom lane