simpledb

Class HeapFile

java.lang.Object

simpledb.HeapFile

All Implemented Interfaces:

java.io.Serializable, 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[]), Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	HeapFile.HeapFileIterator Class for iterating over all tuples of this file

Field Summary

Fields

Modifier and Type	Field and Description
private java.io.File	file
private TupleDesc	tupleDesc

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
Page	deleteTuple(TransactionId tid, Tuple t) Removes the specifed 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 iterator to all the tuples in this file
int	numPages() Returns the number of pages in this HeapFile.
Page	readPage(PageId pid) Reads page from the file with given id
void	writePage(Page page) Write given page to disk

Methods inherited from class java.lang.Object

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

Field Detail

file

private java.io.File file

tupleDesc

private TupleDesc tupleDesc

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.

td - the tuple desc of the 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 eachfor a particular HeapFile. We suggest hashing the absolute file name of the HeapFile has a "unique id," and that you always return the same value 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)

Reads page from the file with given id

Specified by:

readPage in interface DbFile

Parameters:

pid - Page ID

Returns:

Page the read page

writePage

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

Write given page to disk

Specified by:

writePage in interface DbFile

Parameters:

page - Page to write

Throws:

java.io.IOException

numPages

public int numPages()

Returns the number of pages in this HeapFile.

Returns:

The number of pages

insertTuple

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

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 Page deleteTuple(TransactionId tid,
                        Tuple t)
                 throws DbException,
                        TransactionAbortedException

Description copied from interface: DbFile

Removes the specifed 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

Throws:

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

TransactionAbortedException

iterator

public DbFileIterator iterator(TransactionId tid)

Returns iterator to all the tuples in this file

Specified by:

iterator in interface DbFile

Parameters:

tid -

Returns:

DBFileIterator iterator to the tuples