apache pig - Concatenate fields from different relations -

there 2 relations

r1: {f1: chararray, f2: chararray} r2: {f3: chararray, f4: chararray} 

there no unique key in either of relations, number of tuples same.

is there way concatenate corresponding fields of relations output f2, f4 ?

if tuples in right order, can use rank.

r1a = rank r1 * dense; r2a = rank r2 * dense;  r1r2 = join r1a $0, r2a $0;