Bruce Momjian <bruce@momjian.us> writes:
> I was wondering why we mark to_date() as stable and not immutable?
Do you really want to guarantee that it isn't, and never will be,
affected by timezone, datestyle, lc_time, etc? In particular it seems
likely that somebody will eventually complain that since to_char can
output localized month/day names according to lc_time, to_date should be
able to read them.
> Are there people using to_date in indexes or partition functions where
> changing it to immutable would be useful?
By definition, there are not, and I don't recall many complaints from
people trying to. On the other hand, if we mark it immutable and then
in future wish to go back to allowing environment dependencies, we will
have to risk breaking working applications.
regards, tom lane