Re: Re: Request for Patch Feedback: Lag & Lead Window Functions Can Ignore Nulls

On Fri, May 20, 2016 at 1:41 PM, David G. Johnston
<david.g.johnston@gmail.com> wrote:
> How does the relatively new FILTER clause play into this, if at all?

My interpretation of the standard is that FILTER is not allowable for
a window function, and IGNORE|RESPECT NULLS is not allowable for an
ordinary aggregate.

So if we support IGNORE|RESPECT NULLS for anything other than a window
function, we have to come up with our own semantics.

> We already have "STRICT" for deciding whether a function processes nulls.
> Wouldn't this need to exist on the "CREATE AGGREGATE"

STRICT defines behavior at DDL time. I was suggesting that we might
want a DDL-time flag to indicate whether a function can make use of
the query-time IGNORE|RESPECT NULLS option. In other words, most
functions wouldn't know what to do with IGNORE|RESPECT NULLS, but
perhaps some would if we allowed them the option.

Perhaps I didn't understand your point?