On Tue, Aug 18, 2009 at 10:32:35AM +0200, Daniel Verite wrote: > Sam Mason wrote: > > I've just realized another case where it's not consistent; why does the > > following return true: > > > > SELECT row(null) IS NULL; > > > > and yet the following false: > > > > SELECT row(row(null)) IS NULL; > > You're intentionally assuming that row(null) IS NULL evaluating to true > implies that row(null) can be replaced by NULL. As discussed upthread, this > is not the case. But you've still not said how is this useful! I can reformulate maths so that 1+0 <> 1+(0), but this is not useful behavior. Programmers need logical abstractions upon which to build and without them you end up with even more bugs. > > I think I'm saying that PG should be deliberately breaking specified > > behavior and go back to pre-8.2 behavior in this regard. > > But let's run your example with 8.1: > > # SELECT row(null) IS NULL; > ?column? > ---------- > t > > # SELECT row(row(null)) IS NULL; > ?column? > ---------- > f > > These are the same results that you say are inconsistant, so pre-8.2 behavior > doesn't help here... Doh, that'll learn me--I never actually tried older versions. I was just repeating what the docs said about the behavior changing in 8.2. http://www.postgresql.org/docs/current/static/functions-comparison.html#AEN7444 and was mis-interpreting what it was saying. -- Sam http://samason.me.uk/ -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
