org.h2.store
Class PageStore

java.lang.Object
  org.h2.store.PageStore

All Implemented Interfaces:

CacheWriter

public class PageStore
extends java.lang.Object
implements CacheWriter

This class represents a file that is organized as a number of pages. Page 0 contains a static file header, and pages 1 and 2 both contain the variable file header (page 2 is a copy of page 1 and is only read if the checksum of page 1 is invalid). The format of page 0 is:

• 0-47: file header (3 time "-- H2 0.5/B -- \n")
• 48-51: page size in bytes (512 - 32768, must be a power of 2)
• 52: write version (read-only if larger than 1)
• 53: read version (opening fails if larger than 1)

The format of page 1 and 2 is:

• CRC32 of the remaining data: int (0-3)
• write counter (incremented on each write): long (4-11)
• log trunk key: int (12-15)
• log trunk page (0 for none): int (16-19)
• log data page (0 for none): int (20-23)

Page 3 contains the first free list page. Page 4 contains the meta table root page.

Field Summary

static int	PAGE_SIZE_DEFAULT The default page size.
static int	PAGE_SIZE_MAX The biggest possible page size.
static int	PAGE_SIZE_MIN The smallest possible page size.

Constructor Summary

PageStore(Database database, java.lang.String fileName, java.lang.String accessMode, int cacheSizeDefault)
Create a new page store object.

Method Summary

void	addIndex(PageIndex index) Add an index to the in-memory index map.
void	addMeta(PageIndex index, Session session) Add the meta data of an index.
int	allocatePage() Allocate a page.
void	checkpoint() Flush all pending changes to disk, and re-open the log file.
static boolean	checksumTest(byte[] d, int pageId, int pageSize) Check if the stored checksum is correct
void	close() Close the file without further writing.
void	commit(Session session) Mark a committed transaction.
void	compact(boolean fully) Shrink the file so there are no empty pages at the end.
int	copyDirect(int pageId, java.io.OutputStream out) Copy the next page to the output stream.
Data	createData() Create a data object.
void	flushLog() Flush the log file, so that entries can be removed from the cache.
void	free(int pageId) Add a page to the free list.
Cache	getCache()
int	getChangeCount() Get the current change count.
ObjectArray<InDoubtTransaction>	getInDoubtTransactions() Get the list of in-doubt transaction.
Page	getPage(int pageId) Read a page from the store.
int	getPageCount() Get the number of pages (including free pages).
int	getPageSize() Get the page size.
long	getReadCount() Get the file read count since the database was opened.
Record	getRecord(int pos) Get the record if it is stored in the file, or null if not.
int	getRootPageId(int indexId) Get the root page of an index.
int	getSystemTableHeadPos() Get the position of the system table head.
Trace	getTrace() Get the trace writer.
long	getWriteCount() Get the file write count since the database was opened.
long	getWriteCountTotal() Get the file write count since the database was created.
void	incrementChangeCount() Increment the change count.
boolean	isRecoveryRunning() Check whether the recovery process is currently running.
void	logAddOrRemoveRow(Session session, int tableId, Row row, boolean add) A record is added to a table, or removed from a table.
void	logTruncate(Session session, int tableId) A table is truncated.
void	logUndo(Record record, Data old) Write an undo log entry if required.
static SearchRow[]	newSearchRows(int entryCount) Create an array of SearchRow with the given size.
void	open() Open the file and read the header.
void	prepareCommit(Session session, java.lang.String transaction) Prepare a transaction.
Data	readPage(int pos) Read a page.
void	removeMeta(Index index, Session session) Remove the meta data of an index.
void	removeRecord(int pageId) Remove a page from the cache.
void	setInDoubtTransactionState(int sessionId, int pageId, boolean commit) Commit or rollback a prepared transaction after opening a database with in-doubt transactions.
void	setMaxLogSize(long maxSize) Set the maximum log file size in megabytes.
void	update(Page page) Update a page.
void	writeBack(CacheObject obj) Persist a record.
void	writePage(int pageId, Data data) Write a page.

Methods inherited from class java.lang.Object

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

Field Detail

PAGE_SIZE_MIN

public static final int PAGE_SIZE_MIN

The smallest possible page size.

See Also:

Constant Field Values

PAGE_SIZE_MAX

public static final int PAGE_SIZE_MAX

The biggest possible page size.

See Also:

Constant Field Values

PAGE_SIZE_DEFAULT

public static final int PAGE_SIZE_DEFAULT

The default page size.

See Also:

Constant Field Values

Constructor Detail

PageStore

public PageStore(Database database,
                 java.lang.String fileName,
                 java.lang.String accessMode,
                 int cacheSizeDefault)
          throws java.sql.SQLException

Create a new page store object.

Parameters:

database - the database

fileName - the file name

accessMode - the access mode

cacheSizeDefault - the default cache size

Throws:

java.sql.SQLException

Method Detail

copyDirect

public int copyDirect(int pageId,
                      java.io.OutputStream out)
               throws java.sql.SQLException

Copy the next page to the output stream.

Parameters:

pageId - the page to copy

out - the output stream

Returns:

the new position, or -1 if there is no more data to copy

Throws:

java.sql.SQLException

open

public void open()
          throws java.sql.SQLException

Open the file and read the header.

Throws:

java.sql.SQLException

checkpoint

public void checkpoint()
                throws java.sql.SQLException

Flush all pending changes to disk, and re-open the log file.

Throws:

java.sql.SQLException

compact

public void compact(boolean fully)
             throws java.sql.SQLException

Shrink the file so there are no empty pages at the end.

Parameters:

fully - if the database should be fully compressed

Throws:

java.sql.SQLException

getPage

public Page getPage(int pageId)
             throws java.sql.SQLException

Read a page from the store.

Parameters:

pageId - the page id

Returns:

the page

Throws:

java.sql.SQLException

close

public void close()
           throws java.sql.SQLException

Close the file without further writing.

Throws:

java.sql.SQLException

flushLog

public void flushLog()
              throws java.sql.SQLException

Description copied from interface: CacheWriter

Flush the log file, so that entries can be removed from the cache. This is only required if the cache is full and contains data that is not yet written to the log file. It is required to write the log entries to the log file first, because the log file is 'write ahead'.

Specified by:

flushLog in interface CacheWriter

Throws:

java.sql.SQLException

getTrace

public Trace getTrace()

Description copied from interface: CacheWriter

Get the trace writer.

Specified by:

getTrace in interface CacheWriter

Returns:

the trace writer

writeBack

public void writeBack(CacheObject obj)
               throws java.sql.SQLException

Description copied from interface: CacheWriter

Persist a record.

Specified by:

writeBack in interface CacheWriter

Parameters:

obj - the cache entry

Throws:

java.sql.SQLException

logUndo

public void logUndo(Record record,
                    Data old)
             throws java.sql.SQLException

Write an undo log entry if required.

Parameters:

record - the page

old - the old data (if known) or null

Throws:

java.sql.SQLException

update

public void update(Page page)
            throws java.sql.SQLException

Update a page.

Parameters:

page - the page

Throws:

java.sql.SQLException

allocatePage

public int allocatePage()
                 throws java.sql.SQLException

Allocate a page.

Returns:

the page id

Throws:

java.sql.SQLException

free

public void free(int pageId)
          throws java.sql.SQLException

Add a page to the free list. The undo log entry must have been written.

Parameters:

pageId - the page id

Throws:

java.sql.SQLException

createData

public Data createData()

Create a data object.

Returns:

the data page.

getRecord

public Record getRecord(int pos)

Get the record if it is stored in the file, or null if not.

Parameters:

pos - the page id

Returns:

the record or null

readPage

public Data readPage(int pos)
              throws java.sql.SQLException

Read a page.

Parameters:

pos - the page id

Returns:

the page

Throws:

java.sql.SQLException

getPageSize

public int getPageSize()

Get the page size.

Returns:

the page size

getPageCount

public int getPageCount()

Get the number of pages (including free pages).

Returns:

the page count

writePage

public void writePage(int pageId,
                      Data data)
               throws java.sql.SQLException

Write a page.

Parameters:

pageId - the page id

data - the data

Throws:

java.sql.SQLException

removeRecord

public void removeRecord(int pageId)

Remove a page from the cache.

Parameters:

pageId - the page id

logAddOrRemoveRow

public void logAddOrRemoveRow(Session session,
                              int tableId,
                              Row row,
                              boolean add)
                       throws java.sql.SQLException

A record is added to a table, or removed from a table.

Parameters:

session - the session

tableId - the table id

row - the row to add

add - true if the row is added, false if it is removed

Throws:

java.sql.SQLException

commit

public void commit(Session session)
            throws java.sql.SQLException

Mark a committed transaction.

Parameters:

session - the session

Throws:

java.sql.SQLException

prepareCommit

public void prepareCommit(Session session,
                          java.lang.String transaction)
                   throws java.sql.SQLException

Prepare a transaction.

Parameters:

session - the session

transaction - the name of the transaction

Throws:

java.sql.SQLException

getSystemTableHeadPos

public int getSystemTableHeadPos()

Get the position of the system table head.

Returns:

the system table head

addIndex

public void addIndex(PageIndex index)

Add an index to the in-memory index map.

Parameters:

index - the index

addMeta

public void addMeta(PageIndex index,
                    Session session)
             throws java.sql.SQLException

Add the meta data of an index.

Parameters:

index - the index to add

session - the session

Throws:

java.sql.SQLException

removeMeta

public void removeMeta(Index index,
                       Session session)
                throws java.sql.SQLException

Remove the meta data of an index.

Parameters:

index - the index to remove

session - the session

Throws:

java.sql.SQLException

setMaxLogSize

public void setMaxLogSize(long maxSize)

Set the maximum log file size in megabytes.

Parameters:

maxSize - the new maximum log file size

setInDoubtTransactionState

public void setInDoubtTransactionState(int sessionId,
                                       int pageId,
                                       boolean commit)
                                throws java.sql.SQLException

Commit or rollback a prepared transaction after opening a database with in-doubt transactions.

Parameters:

sessionId - the session id

pageId - the page where the transaction was prepared

commit - if the transaction should be committed

Throws:

java.sql.SQLException

getInDoubtTransactions

public ObjectArray<InDoubtTransaction> getInDoubtTransactions()

Get the list of in-doubt transaction.

Returns:

the list

isRecoveryRunning

public boolean isRecoveryRunning()

Check whether the recovery process is currently running.

Returns:

true if it is

newSearchRows

public static SearchRow[] newSearchRows(int entryCount)

Create an array of SearchRow with the given size.

Parameters:

entryCount - the number of elements

Returns:

the array

getWriteCountTotal

public long getWriteCountTotal()

Get the file write count since the database was created.

Returns:

the write count

getWriteCount

public long getWriteCount()

Get the file write count since the database was opened.

Returns:

the write count

getReadCount

public long getReadCount()

Get the file read count since the database was opened.

Returns:

the read count

logTruncate

public void logTruncate(Session session,
                        int tableId)
                 throws java.sql.SQLException

A table is truncated.

Parameters:

session - the session

tableId - the table id

Throws:

java.sql.SQLException

getRootPageId

public int getRootPageId(int indexId)

Get the root page of an index.

Parameters:

indexId - the index id

Returns:

the root page

getCache

public Cache getCache()

checksumTest

public static boolean checksumTest(byte[] d,
                                   int pageId,
                                   int pageSize)

Check if the stored checksum is correct

Parameters:

d - the data

pageId - the page id

pageSize - the page size

Returns:

true if it is correct

incrementChangeCount

public void incrementChangeCount()

Increment the change count. To be done after the operation has finished.

getChangeCount

public int getChangeCount()

Get the current change count. The first value is 1

Returns:

the change count