Re: 8.2.4 Won't Build 8.1 Functional Indexes

Well, the one index:
CREATE INDEX acceptedbilling_to_date_accepted_billing_dt_idx
ON acceptedbilling
USING btree
(to_date(accepted_billing_dt::text, 'yyyymmdd'::text));.

Reject:
ERROR: functions in index expression must be marked IMMUTABLE
SQL state: 42P17

Is actually a date stored in a varchar field (stupid I know, but it's a
continual fight between the me (the dba), management, and our COBOL
programmers). I was indexing it as a date so that I can treat it as a date
in some of the non-COBOL programs/utilities that we have written.

The second index is rather stupid, it was an early index before I figured
out how to split a timestamp.

Anyway, is there a way to make the first index work? Otherwise we end up
with a seq scan on our billing table which is very painful.

Thanks,

Chris

On 6/6/07, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> > You can't do this because to_date and other functions are not immutable.
> > 8.2 seems to be more picky about this -- the date conversions of
> > timestamptz columns are dependent on the current timezone.
>
> The reason 8.2 is more picky is that the function is less immutable
> thanks to the addition of locale-dependent functionality:
> http://archives.postgresql.org/pgsql-committers/2006-11/msg00264.php
>
> I gather that the underlying column is timestamp without tz, or it would
> never have worked in 8.1 either. That being the case, these index
> definitions seem pretty darn stupid anyway --- why aren't you just
> indexing on date_trunc or a plain cast to date?
>
> regards, tom lane
>