什么导致加入Pig的空结果？

Question

我有这样的脚本：

E1 = LOAD 'dictionaries.txt' using PigStorage() as (id : int, src_id : int, source_code : chararray, src_code  : chararray , src_description  : chararray, group_code  : chararray);
iboa_dict = FILTER E1 by source_code == 'IBOA';

iboa_events = LOAD 'stage.iboa_events' USING org.apache.hcatalog.pig.HCatLoader();
iboa_events_join = join iboa_events by inst_inno_id, iboa_dict by src_id;

我正在尝试：

a =                 foreach iboa_events_join generate iboa_events::cont_phone_number as phone_number, iboa_events::inst_start_ts as event_date;

但我得到空洞的结果。

获得anythig的唯一方法是只生成一列：

a = foreach iboa_events_join generate iboa_events::cont_phone_number as phone_number; 

你知道什么会导致这种奇怪的行为吗？

此致 的Pawel