code: private LinkedHashMap<String, Long> getPrefixRefs(String field) {
      if (fieldReferences.containsKey(field)) {
        FieldReferences fr = fieldReferences.get(field);
        if (!prefixReferences.containsKey(field)) {
          LinkedHashMap<String, Long> refs = new LinkedHashMap<String, Long>();
          try {
            IndexInput inPrefix = indexInputList.get("prefix");
            inPrefix.seek(fr.refPrefix);
            for (int i = 0; i < fr.numberOfPrefixes; i++) {
              Long ref = inPrefix.getFilePointer();
              String prefix = inPrefix.readString();
              refs.put(prefix, ref);
            }
          } catch (Exception e) {
            log.error(e);
            refs.clear();
          }
          prefixReferences.put(field, refs);
          return refs;
        } else {
          return prefixReferences.get(field);
        }
      } else {
        return null;
      }
    }
docs: Gets the prefixes.
  
  @param field
  the field
  @return the prefixes