@Override
    public ByteSegmentRef first() {
      if (!hasRows) {
        return null;
      }

      // Position to beginning.
      readIndex = 0;
      isNextEof = false;

      return internalRead();
    }
Setup for a match outright.
@param hashMapStore
@param refWord
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/mapjoin/fast/VectorMapJoinFastBytesHashMapStore.java