I agree with Alan on all counts. I think the confusing part is that null is overloaded. Alas.
2012/11/5 Alan Gates <[email protected]> > Better in terms of semantics or terms of documentation? We can't change > the semantics of null in Pig; it's been that way the whole time. Plus this > concept of unknown data is important in data processing. If we had it to > do over again we could name it 'unknown' instead of null, but it seems late > for that now. > > Alan. > > On Nov 2, 2012, at 3:40 PM, Cheolsoo Park wrote: > > > Hi Alan, > > > > Recently, I have seen several similar confusions about nulls in Pig. For > > example, here is another discussion: > > https://issues.apache.org/jira/browse/PIG-3021. > > > > We are documenting them, but apparently, many users find it confusing. I > am > > wondering if there is anything that we can do better. > > > > Thanks, > > Cheolsoo > > > > On Fri, Nov 2, 2012 at 3:33 PM, Alan Gates <[email protected]> > wrote: > > > >> To give some context, the null semantics in Pig follow SQL's. In SQL, > >> null is viral, so any operation with null results in null. The idea is > >> that null means unknown, not empty. So concat('x', unknown) = unknown. > >> > >> Alan. > >> > >> On Nov 2, 2012, at 3:09 PM, Yang wrote: > >> > >>> looks a more intuitive result should be "something" , right? > >>> > >>> but on my system it gave null > >> > >> > >
