code: public boolean setMetadata(int iid, Object metaData) {
  		if (iid < 0 || iid > loadCounter) {
  			System.out.println("Internal id " + iid + " is out of range!");
  			return false;
  		}
  		MetaDataEntity mde = new MetaDataEntity(iid, metaData);
  		PrimaryIndex<Integer, MetaDataEntity> primaryIndex = iidToMetadataDB.getPrimaryIndex(Integer.class,
  				MetaDataEntity.class);
  
  		if (primaryIndex.contains(iid)) {
  			primaryIndex.put(null, mde);
  			return true;
  		} else {
  			return false;
  		}
  	}
docs: This method is used to set the metadata of a previously indexed vector. If the metadata is already set,
  this methods replaces it.
  
  @param iid
  The internal id of the vector
  @param metaData
  A java object of any class with the @persistent annotation
  @return true if metadata is successfully set, false otherwise