core/src/main/java/com/orientechnologies/orient/core/iterator/ORecordIteratorClusters.java
@Override
  public ORecordIteratorClusters<REC> begin() {
    if (clusterIds.length == 0)
      return this;

    browsedRecords = 0;
    currentClusterIdx = 0;
    current.setClusterId(clusterIds[currentClusterIdx]);

    updateClusterRange();

    resetCurrentPosition();
    nextPosition();

    final ORecord record = getRecord();
    currentRecord = readCurrentRecord(record, 0);

    if (currentRecord != null && !include(currentRecord)) {
      currentRecord = null;
      hasNext();
    }

    return this;
  }
@Override
  public ORecordIteratorClusters<REC> begin() {
    if (clusterIds.length == 0)
      return this;

    browsedRecords = 0;
    currentClusterIdx = 0;
    current.setClusterId(clusterIds[currentClusterIdx]);

    updateClusterRange();

    resetCurrentPosition();
    nextPosition();

    final ORecord record = getRecord();
    currentRecord = readCurrentRecord(record, 0);

    if (currentRecord != null && !include(currentRecord)) {
      currentRecord = null;
      hasNext();
    }

    return this;
  }
Move the iterator to the begin of the range. If no range was specified move to the first record of the cluster.

@return The object itself