public interface VertexIdDataIterator<I extends org.apache.hadoop.io.WritableComparable,T>
extends VertexIdIterator<I>
Special iterator that reuses vertex ids and data objects so that the
lifetime of the object is only until next() is called.
Vertex id ownership can be released if desired through
releaseCurrentVertexId(). This optimization allows us to cut down
on the number of objects instantiated and garbage collected.