bda20adf_Cascading_2_1_User_Guide__Pipe_type
[Purpose] sort/group on field values; optionally merge two or more streams with identical fields [Input] two or more tuple streams with identical fields [Output] a single tuple stream, grouped on key field(s) with optional secondary sort [Pipe type] 
GroupBy
P i p e
S u b A s s e m b l y
E a c h
M e r g e
G r o u p B y
E v e r y
C o G r o u p
H a s h J o i n
Cascading 2.1 User Guide
Pipe type