@Override
    public boolean equals(Object obj) {
        VdsHit rhs = (VdsHit)obj;
        return super.equals(obj) &&
               docId.equals(rhs.docId) &&
               summary.equals(rhs.summary);
    }
Obtain the local document id of this hit.

@return The local document id.
searchlib/src/main/java/com/yahoo/searchlib/aggregation/VdsHit.java