code: public final int getDBIndex(byte[] key) {
          if(key == null) return -1;
          
          byte[] metaBytes = _index.lookup(key);
          if(metaBytes == null) return -1;
          
          IndexMeta meta = IndexMeta.parse(metaBytes);
          if(meta == null) return -1;
          
          return meta.getDataAddr();
      }
docs: Gets the underlying DB index associated with the specified <code>key</code>.
  
  @param key - the key
  @return <code>-1</code> if the specified <code>key</code> is <code>null</code> or not found.