David Fetter <david@fetter.org> writes:
> Apart from the medians, which "median-like" aggregates do you have in
> mind to start with? If you can provide examples of "median-like"
> aggregates that people might need to implement as user-defined
> aggregates, or other places where people would use this machinery, it
> will make your case stronger for this refactoring.
There would be plenty of scope to re-use the machinery without any
SQL-level extensions. All you need is a polymorphic aggregate
transition function that maintains a tuplestore or whatever.
I don't see that extra syntax in CREATE AGGREGATE is really buying
much of anything.
regards, tom lane