heap
Class Scan

java.lang.Object
  heap.Scan

All Implemented Interfaces:

GlobalConst

public class Scan

extends java.lang.Object

implements GlobalConst

A Scan object is created ONLY through the function openScan of a HeapFile. It supports the getNext interface which will simply retrieve the next record in the heapfile. An object of type scan will always have pinned one directory page of the heapfile.

Field Summary

Fields inherited from interface global.GlobalConst

INVALID_PAGE, MAX_NAME, MAX_SPACE, MAXATTRNAME, MAXFILENAME, MAXINDEXNAME, MINIBASE_BUFFER_POOL_SIZE, MINIBASE_DB_SIZE, MINIBASE_DEFAULT_SHAREDMEM_SIZE, MINIBASE_MAX_TRANSACTIONS, MINIBASE_MAXARRSIZE, MINIBASE_PAGESIZE, NUMBUF

Constructor Summary

Scan(Heapfile hf)
The constructor pins the first directory page in the file and initializes its private data members from the private data member from hf

Method Summary

void	closescan() Closes the Scan object
Tuple	getNext(RID rid) Retrieve the next record in a sequential scan
boolean	position(RID rid) Position the scan cursor to the record with the given rid.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Scan

public Scan(Heapfile hf)
     throws InvalidTupleSizeException,
            java.io.IOException

The constructor pins the first directory page in the file and initializes its private data members from the private data member from hf

Parameters:

hf - A HeapFile object

Throws:

InvalidTupleSizeException - Invalid tuple size

java.io.IOException - I/O errors

Method Detail

getNext

public Tuple getNext(RID rid)
              throws InvalidTupleSizeException,
                     java.io.IOException

Retrieve the next record in a sequential scan

Parameters:

rid - Record ID of the record

Returns:

the Tuple of the retrieved record.

Throws:

InvalidTupleSizeException - Invalid tuple size

java.io.IOException - I/O errors

position

public boolean position(RID rid)
                 throws InvalidTupleSizeException,
                        java.io.IOException

Position the scan cursor to the record with the given rid.

Parameters:

rid - Record ID of the given record

Returns:

true if successful, false otherwise.

Throws:

InvalidTupleSizeException - Invalid tuple size

java.io.IOException - I/O errors

closescan

public void closescan()

Closes the Scan object