code: public void open(final MutableObjectIterator<BT> buildSide, final MutableObjectIterator<PT> probeSide)
  		throws IOException {
  
  		open(buildSide, probeSide, false);
  	}
docs: Opens the hash join. This method reads the build-side input and constructs the initial
  hash table, gradually spilling partitions that do not fit into memory.
  
  @param buildSide Build side input.
  @param probeSide Probe side input.
  @throws IOException Thrown, if an I/O problem occurs while spilling a partition.