2010/8/18 Tom Lane <t...@sss.pgh.pa.us>: > David Fetter <da...@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. >
Have we to use a transisdent function? If we implement median as special variant of aggregate - because we need to push an sort, then we can skip a transident function function - and call directly final function. This mechanism is used for aggregates with ORDER BY now. So there can be a special path for direct call of final func. There is useles to call transident function. Regards Pavel > regards, tom lane > -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
