Florian Pflug <f...@phlo.org> writes: > On Jan10, 2014, at 15:49 , Tom Lane <t...@sss.pgh.pa.us> wrote: >> Also, it might be reasonable for both the regular and the inverse >> transition functions to be strict. If a null entering the window >> does not matter, then a null exiting the window doesn't either, no?
> That's not true, I think, unless we're special-casing strict transition > functions somewhere. AFAICS, an aggregate with a strict transition function > will produce the state NULL whenever any of the inputs was NULL, i.e. we won't > ever transition out of the NULL state once we got there. Nope, not the case; read xaggr.sgml and/or the CREATE AGGREGATE reference page. An aggregate with a strict transition function essentially just ignores null input rows. I suspect the inverse transition function could just be made strict with a similar special-case rule (viz, keep the old transition value when deleting a null input from the window); but maybe I'm missing something and it has to work harder than that anyway. regards, tom lane -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers