SAP Lucene Sorting Optimization - readCounter for Full Table Scans

private long readCounter;
private Object[] allValues; 
InternalFieldComparator2(int numHits, String fieldP, final LuceneFieldSorter sorter)
{
  readCounter = 0;
  allValues = null;
}
/*
For each read access to a Lucene document the counter is increased. If the counter is higher than 4000,  a full table scan is assumed, and the old approach of retrieving all Lucene index documents is used. The old approach is faster if all documents have to be read anyway. 
*/
public Object getValueFromDoc(int doc)
{
  readCounter ++;
  if (readCounter > 4000) 
  {      
    if (allValues == null) {
     try 
     {
       allValues = getLuceneValues(field, reader);
     } 
     catch (IOException e) 
     {
        allValues = new Object[reader.maxDoc()];
    }
}
 else ...