
171Large-Scale RDF Processing with MapReduce
multisets of mappings are brought together such that all compatible mappings can
be processed on the same machine. Our MAPSIN join technique computes the join
between p
1
and p
2
in a single map phase. At the beginning, the map phase is ini-
tialized with a parallel distributed HBase table scan for the rst triple pattern p
1
where each machine retrieves only those mappings that are locally available. This
is achieved by utilizing a mechanism for allocating local records to map functions,
which is supported by the MapReduce input format for HBase. The map function is
invoked for each retrieved mapping ...