In a previous version I've had to write a UDF called NOT that I invoke with
T = filter U by my.udf.NOT($2 is null); -- and T = filter U by my.udf.NOT(IsEmpty($3)); it was for an older ver of pig..., soymmv. 2010/4/21 Mridul Muralidharan <mrid...@yahoo-inc.com> > > In case of co-group, if nothing matched the group key, you get an empty > bag, not null. > > So checking for COUNT(alias) == 0 is what you need. > > > Regards, > Mridul > > > > On Wednesday 21 April 2010 03:37 PM, Alexander Schätzle wrote: > >> Hello, >> >> I want to use IS NULL in a FILTER but the behavior seems to be a Bug: >> >> I make a LeftJoin with a result of 7 tuples with fields 's' and 'nick'. >> 4 tuples have a value for 'nick', the other 3 don't have a value for >> 'nick'. >> Afterwards I want to filter so that only the 3 tuples without a nick are >> left: >> >> Filter1 = FILTER LeftJoin1 BY nick is null; >> >> But as result I get all 7 tuples but all of them now don't have a nick! >> So what's going on there!? >> If I use IS NOT NULL instead I get all 7 tuples unchanged! >> >> >> This is the complete script, input data can be found in the attachment: >> >> indata = LOAD 'foaf' USING PigStorage() AS (s,p,o); >> >> f1 = FILTER indata BY p == 'ex:type' AND o == 'ex:Person'; >> BGP1 = FOREACH f1 GENERATE s AS s; >> >> f1 = FILTER indata BY p == 'ex:nick'; >> BGP2 = FOREACH f1 GENERATE s AS s, o AS nick; >> >> lj1 = JOIN BGP1 BY s LEFT OUTER, BGP2 BY s; >> LEFTJOIN1 = FOREACH lj1 GENERATE $0 AS s, $2 AS nick; >> >> FILTER1 = FILTER LEFTJOIN1 BY nick is null; >> >> STORE FILTER1 INTO 'outfile' USING PigStorage(); >> >> >> Can anyone help me what's going wrong? >> >> Thx, >> Alex >> >> >
