"David G. Johnston" <david.g.johnston@xxxxxxxxx> writes: > On Thu, Mar 26, 2015 at 1:49 PM, Timothy Garnett <tgarnett@xxxxxxxxxxx> > wrote: >> but if that is declared strict then it would take the first non-null value >> and return A in my second example, if declared non-strict then the initial >> state would be fed as null rather then the first value. Is there a way to >> declare the function non-strict (so that null values are passed) but still >> have it initialize to the first value like it would if it was strict? > You want NULL to both mean "not initialized" and "unknown value" which is > impossible and SQL does not provide any other universal literal that means > one or the other. Yeah. You need distinct representations for "nothing seen yet" and "saw a NULL"; the built-in behavior doesn't suffice for this. One idea is for the state value to be of anyarray type: initially null, and a one-element array containing the first input value once you've seen that. It strikes me though that this aggregate is ill-defined by nature. In particular, if you're going to treat NULL as being a real data value, then what're you gonna return when there were no input rows? You won't be able to distinguish "no input rows" from "first input row had a NULL". Maybe you should rethink whatever activity you were wanting it for. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
