private ArrayList<ArrayDBIDs> buildOneDimIndexes(Relation<? extends NumberVector> relation){
  final int dim=RelationUtil.dimensionality(relation);
  ArrayList<ArrayDBIDs> subspaceIndex=new ArrayList<>(dim + 1);
  SortDBIDsBySingleDimension comp=new VectorUtil.SortDBIDsBySingleDimension(relation);
  for (int i=0; i < dim; i++) {
    ArrayModifiableDBIDs amDBIDs=DBIDUtil.newArray(relation.getDBIDs());
    comp.setDimension(i);
    amDBIDs.sort(comp);
    subspaceIndex.add(amDBIDs);
  }
  return subspaceIndex;
}

private ArrayList < ArrayDBIDs > buildOneDimIndexes ( Relation < ? extends NumberVector > relation ) { final int dim = RelationUtil . dimensionality ( relation ) ; ArrayList < ArrayDBIDs > subspaceIndex = new ArrayList < > ( dim + 1 ) ; SortDBIDsBySingleDimension comp = new VectorUtil . SortDBIDsBySingleDimension ( relation ) ; for ( int i = 0 ; i < dim ; i ++ ) { ArrayModifiableDBIDs amDBIDs = DBIDUtil . newArray ( relation . getDBIDs ( ) ) ; comp . setDimension ( i ) ; amDBIDs . sort ( comp ) ; subspaceIndex . add ( amDBIDs ) ; } return subspaceIndex ; }
calculates " index structures " for every attribute , i . e . sorts a modifiablearray of every dbid in the database for every dimension and stores them in a list
