Re: CAST Within EXCLUSION constraint

On Aug 20, 2013, at 6:50 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> 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…

Thanks,

David