On 2013-08-29 18:29:34 -0400, Tom Lane wrote: > Andres Freund <and...@2ndquadrant.com> writes: > > On 2013-08-29 15:55:13 -0400, Tom Lane wrote: > >> For context see the thread starting here: > >> http://www.postgresql.org/message-id/aanlktikv5ok2ts8t6v+gsapte3n6tjq1jpphmzhg2...@mail.gmail.com > >> In that thread we agreed that this "policy" might be rather squishy, > >> but we should at least think hard about whether it would be wise to create > >> built-in aggregates with the same name and different numbers of arguments. > > > I vote for abolishing that policy or maybe weakinging it. As you comment > > somewhere downthread the policy just prohibits core functions, but even > > for those it looks too strong for me. There are some useful variadic > > aggregates I'd like to see and I don't think that the kind of errors > > prevented by the policy are frequent enough to warrant a blanket > > prohibition. > > Well, I dunno. We had two different "bug reports" caused by this type of > confusion before string_agg even got out of beta, both from intelligent > people. So I'm not about to discount the potential for confusion. > > As we said originally, this is a policy that might be broken for > sufficiently strong cause --- but I don't want to just forget about > the risks.
> > I'd say we let the check in there but have a list of exceptions in it so > > that one has to explicitly think about the issue before adding the > > function. > > That's pretty much how the tests in opr_sanity work now. I basically mean that we should adapt the paragraph you quoted upthread to roughly say something like: -- Check that there are not aggregates with the same name and different -- numbers of arguments. For many aggregates - look for string_agg in -- the archives for an example - the risk of confusing novices, which -- place ORDER BY in the wrong place, seems too big. If an aggregate is -- deemed not to be likely to cause such a problem or provides a feature -- which doesn't seem possibly to provide in another way that, add an -- excception for it. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
