How to remove the field key from bags tuples after a GROUP ?

[Vincent Barat]

Hi,

First, I group 2 tables using a key (named sid):
rich_sessions = GROUP sessions BY sid, activities BY sid;

After this operation, all the tuples in the bag "activities" start 
with the same "sid" field.
This field is long (64 bytes) and I would like to remove it from all 
activity tuples in order to save space before storing this 
rich_sessions in a file.

Is there any way to do this ?

Thank for your help,