Re: general purpose array_sort

On Tue, Oct 29, 2024 at 12:48 AM Aleksander Alekseev
<aleksander(at)timescale(dot)com> wrote:.
>
> 0001:
>
> > +{ oid => '8810', descr => 'sort array',
> > + proname => 'array_sort', provolatile => 'v', prorettype => 'anyarray',
> > + proargtypes => 'anyarray', prosrc => 'array_sort'},
>
> I would expect that array_sort() should be IMMUTABLE. Is there a
> reason for it to be VOLATILE?
>

https://www.postgresql.org/docs/current/sql-createfunction.html says:

IMMUTABLE indicates that the function cannot modify the database and always
returns the same result when given the same argument values; that is, it does
not do database lookups or otherwise use information not directly present in its
argument list. If this option is given, any call of the function with
all-constant arguments can be immediately replaced with the function value.

+ {
+ typentry = lookup_type_cache(elmtyp, TYPECACHE_LT_OPR);
+ if (!OidIsValid(typentry->lt_opr))
+ ereport(ERROR,
+ (errcode(ERRCODE_UNDEFINED_FUNCTION),
+ errmsg("could not identify ordering operator for type %s",
+ format_type_be(elmtyp))));

This error can happen. I think this conflicts with the doc IMMUTABLE
description.