Synchronized scanning - response (9) by AdamL

All AMP join step, by way of row hash match scan,using merger join .After that, explain says the input tables for joins will not be cached in memory, but they are eligible for synchronized scanning. Then we sort to order Spool1 by rowhash.
>> Just curious whats the role of rowhash match scan here?
Does it help in doing piggyback, under synchronized scanning?