2009/12/20 Tom Lane <t...@sss.pgh.pa.us>: > Pavel Stehule <pavel.steh...@gmail.com> writes: >> I am thinking about implementation of median function. This function >> should be implemented in two ways: > >> a) direct entering an ORDER BY clause for median funcall in gram.y >> b) general support for "preordered aggregates". > >> I prefer plan b, because there are more similar aggregates - like >> Quantiles. > > This seems like a great deal of mechanism to solve a very localized > problem. >
plan a doesn't block plan b - it is very simple. So we can start with a. > I think that we've already expanded the capabilities of aggregates > a great deal for 8.5, and we should let it sit as-is for a release > or two and see what the real user demand is for additional features. > > I'm particularly concerned by the fact that the feature set is already > far out in front of what the planner can optimize effectively (e.g., > there's no ability to combine the work when multiple aggregates need the > same sorted data). The more features we add on speculation, the harder > it's going to be to close that gap. I didn't thing about this optimalisation, but this point could not be impossible. Bigger problem is using of indexes. > > Another risk is that features added now might preclude adding others > later. > sure. It was my question, what is preferred. 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
