rmcgehee(at)gmail(dot)com writes:
> The lag() window function is documented to accept a default argument.
> However, if lag is applied to either a float or a real (and possibly other
> types as well), adding a default gives an error.
The default argument has to be the same type as the value argument;
in your failing example, it is not. Perhaps the documentation could be
more explicit about that.
regards, tom lane