Pig Difference between inner bag and outer bag

Question

Can someone explain to me the difference between inner bag and outer bag with example? Thanks in advance

Answer 1

Outer Bag:

An outer bag is nothing but a relation. In the below example, A is a relation or bag of tuples. You can think of this bag as an outer bag.

A = LOAD 'data' as (f1:int, f2:int, f3:int); 
DUMP A; 

(1,2,3) 
(4,2,1) 
(8,3,4) 
(4,3,3)

Inner bag:

An inner bag is a relation inside any other bag.

Example:

Now, suppose we group relation A by the first field to form relation X.

In this example, X is a relation or bag of tuples. The tuples in relation X have two fields. The first field is type int. The second field is type bag; you can think of this bag as an inner bag.

X = GROUP A BY f1; 
DUMP X; 
(1,{(1,2,3)}) 
(4,{(4,2,1),(4,3,3)}) 
(8,{(8,3,4)})