simpledb

Class HeapFile

java.lang.Object

simpledb.HeapFile

All Implemented Interfaces:

DbFile

public class HeapFile
extends java.lang.Object
implements DbFile

HeapFile is an implementation of a DbFile that stores a collection of tuples in no particular order. Tuples are stored on pages, each of which is a fixed size, and the file is simply a collection of those pages. HeapFile works closely with HeapPage. The format of HeapPages is described in the HeapPage constructor.

Author:

Sam Madden

See Also:

HeapPage.HeapPage(simpledb.HeapPageId, byte[])

Constructor Summary

Constructors

Constructor and Description
HeapFile(java.io.File f, TupleDesc td) Constructs a heap file backed by the specified file.

Method Summary

Modifier and Type	Method and Description
java.util.ArrayList<Page>	deleteTuple(TransactionId tid, Tuple t) Removes the specified tuple from the file on behalf of the specified transaction.
java.io.File	getFile() Returns the File backing this HeapFile on disk.
int	getId() Returns an ID uniquely identifying this HeapFile.
TupleDesc	getTupleDesc() Returns the TupleDesc of the table stored in this DbFile.
java.util.ArrayList<Page>	insertTuple(TransactionId tid, Tuple t) Inserts the specified tuple to the file on behalf of transaction.
DbFileIterator	iterator(TransactionId tid) Returns an iterator over all the tuples stored in this DbFile.
int	numPages() Returns the number of pages in this HeapFile.
Page	readPage(PageId pid) Read the specified page from disk.
void	writePage(Page page) Push the specified page to disk.

Methods inherited from class java.lang.Object

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

Constructor Detail

HeapFile

public HeapFile(java.io.File f,
                TupleDesc td)

Constructs a heap file backed by the specified file.

Parameters:

f - the file that stores the on-disk backing store for this heap file.

Method Detail

getFile

public java.io.File getFile()

Returns the File backing this HeapFile on disk.

Returns:

the File backing this HeapFile on disk.

getId

public int getId()

Returns an ID uniquely identifying this HeapFile. Implementation note: you will need to generate this tableid somewhere ensure that each HeapFile has a "unique id," and that you always return the same value for a particular HeapFile. We suggest hashing the absolute file name of the file underlying the heapfile, i.e. f.getAbsoluteFile().hashCode().

Specified by:

getId in interface DbFile

Returns:

an ID uniquely identifying this HeapFile.

getTupleDesc

public TupleDesc getTupleDesc()

Returns the TupleDesc of the table stored in this DbFile.

Specified by:

getTupleDesc in interface DbFile

Returns:

TupleDesc of this DbFile.

readPage

public Page readPage(PageId pid)

Description copied from interface: DbFile

Read the specified page from disk.

Specified by:

readPage in interface DbFile

writePage

public void writePage(Page page)
               throws java.io.IOException

Description copied from interface: DbFile

Push the specified page to disk.

Specified by:

writePage in interface DbFile

Parameters:

page - The page to write. page.getId().pageno() specifies the offset into the file where the page should be written.

Throws:

java.io.IOException - if the write fails

numPages

public int numPages()

Returns the number of pages in this HeapFile.

insertTuple

public java.util.ArrayList<Page> insertTuple(TransactionId tid,
                                             Tuple t)
                                      throws DbException,
                                             java.io.IOException,
                                             TransactionAbortedException

Description copied from interface: DbFile

Inserts the specified tuple to the file on behalf of transaction. This method will acquire a lock on the affected pages of the file, and may block until the lock can be acquired.

Specified by:

insertTuple in interface DbFile

Parameters:

tid - The transaction performing the update

t - The tuple to add. This tuple should be updated to reflect that it is now stored in this file.

Returns:

An ArrayList contain the pages that were modified

Throws:

DbException - if the tuple cannot be added

java.io.IOException - if the needed file can't be read/written

TransactionAbortedException

deleteTuple

public java.util.ArrayList<Page> deleteTuple(TransactionId tid,
                                             Tuple t)
                                      throws DbException,
                                             TransactionAbortedException

Description copied from interface: DbFile

Removes the specified tuple from the file on behalf of the specified transaction. This method will acquire a lock on the affected pages of the file, and may block until the lock can be acquired.

Specified by:

deleteTuple in interface DbFile

Parameters:

tid - The transaction performing the update

t - The tuple to delete. This tuple should be updated to reflect that it is no longer stored on any page.

Returns:

An ArrayList contain the pages that were modified

Throws:

DbException - if the tuple cannot be deleted or is not a member of the file

TransactionAbortedException

iterator

public DbFileIterator iterator(TransactionId tid)

Description copied from interface: DbFile

Returns an iterator over all the tuples stored in this DbFile. The iterator must use BufferPool.getPage(simpledb.TransactionId, simpledb.PageId, simpledb.Permissions), rather than DbFile.readPage(simpledb.PageId) to iterate through the pages.

Specified by:

iterator in interface DbFile

Returns:

an iterator over all the tuples stored in this DbFile.