* Tom Lane ([EMAIL PROTECTED]) wrote: > That's not really the flavor of solution I'd like to have. Ideally, > it'd actually *work* to write > > my_ffunc(my_sfunc(my_sfunc(null, 1), 2)) > > and get the same result as aggregating over the values 1 and 2. The > trick is to make sure that my_sfunc and my_ffunc can only be used > together. Maybe we do need a type for each such aggregate ...
In general I like this idea but there are some complications, the main one being where would the memory be allocated? I guess we could just always use the QueryContext. The other issue is, in the above scenario is it acceptable to modify the result of my_sfunc(null, 1) in the ,2 call? Normally it's unacceptable to modify your input, aggregates get a special exception when called as an aggregate, but in this case you'd have to copy the entire custom structure underneath, I'd think. As for a type for each such aggregate, that seems reasonable to me, honestly. I'd like for the type creation to be reasonably simple though, if possible. ie: could we just provide NULLs for the input/output functions instead of having to implement functions that just return an error? Or perhaps have a polymorphic function which can be reused that just returns an error. Additionally, we'd have to be able to mark the types as being polymorhpic along the same lines as anyelement/anyarray. Hopefully that's already easy, but if not it'd be nice if it could be made easy... Thanks, Stephen
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