public HeapFileIterator(TransactionId tid, HeapFile file) {
   _transactionId = tid;
   _file = file;
   _currentPageId = 0;
   _numPages = _file.numPages();
   //			System.out.println("numpages "+_numPages);
 }
 /** Unit test for HeapFile.numPages() */
 @Test
 public void numPages() throws Exception {
   assertEquals(1, hf.numPages());
   // assertEquals(1, empty.numPages());
 }