I see a sort is called when DISTINCT is used on aggregates, also for
the LIST aggregate. Some quick tests reveal that ordering is
preserved. Is this assumption reliable in v2.1.2? I know it says
"ordering is implementation defined" on LIST, but I don't want the
official answer, just want to know if it's reliable to use this as a
workaround (in v2.1.2) until something better comes up. Thank you.