ohh, or in this case... T = filter U by IsEmpty(alias);
would do the trick. On Wed, Apr 21, 2010 at 10:25 AM, hc busy <hc.b...@gmail.com> wrote: > 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 >>> >>> >> >
