Package com.orientechnologies.orient.core.storage.cache

Interface OReadCache

All Known Implementing Classes:

AsyncReadCache, ODirectMemoryOnlyDiskCache

public interface OReadCache

This class is heart of OrientDB storage model it presents disk backed data cache which works with direct memory.

Model of this cache is based on page model. All direct memory area is mapped to disk files and each file is split on pages. Page is smallest unit of work. The amount of RAM which can be used for data manipulation is limited so only a subset of data will be really loaded into RAM on demand, if there is not enough RAM to store all data, part of them will by flushed to the disk. If disk cache is closed all changes will be flushed to the disk.

Since:

14.03.13

Author:

Andrey Lomakin (a.lomakin-at-orientdb.com)

Field Summary

Fields

Modifier and Type	Field	Description
static final int	MIN_CACHE_SIZE	Minimum size of memory which may be allocated by cache (in pages).

Method Summary

Modifier and Type	Method	Description
long	addFile(String fileName, long fileId, OWriteCache writeCache)
long	addFile(String fileName, OWriteCache writeCache)
OCacheEntry	allocateNewPage(long fileId, OWriteCache writeCache, OLogSequenceNumber startLSN)
void	changeMaximumAmountOfMemory(long calculateReadCacheMaxMemory)
void	clear()
void	closeFile(long fileId, boolean flush, OWriteCache writeCache)
void	closeStorage(OWriteCache writeCache)	Closes all files inside of write cache and flushes all associated data.
void	deleteFile(long fileId, OWriteCache writeCache)
void	deleteStorage(OWriteCache writeCache)
long	getUsedMemory()
OCacheEntry	loadForRead(long fileId, long pageIndex, OWriteCache writeCache, boolean verifyChecksums)
OCacheEntry	loadForWrite(long fileId, long pageIndex, OWriteCache writeCache, boolean verifyChecksums, OLogSequenceNumber startLSN)
void	releaseFromRead(OCacheEntry cacheEntry)
void	releaseFromWrite(OCacheEntry cacheEntry, OWriteCache writeCache, boolean changed)
OCacheEntry	silentLoadForRead(long extFileId, int pageIndex, OWriteCache writeCache, boolean verifyChecksums)
void	truncateFile(long fileId, OWriteCache writeCache)

Field Details

MIN_CACHE_SIZE

static final int MIN_CACHE_SIZE

Minimum size of memory which may be allocated by cache (in pages). This parameter is used only if related flag is set in constrictor of cache.

See Also:

• Constant Field Values

Method Details

addFile

long addFile(String fileName,
 OWriteCache writeCache)
      throws IOException

Throws:

IOException

addFile

long addFile(String fileName,
 long fileId,
 OWriteCache writeCache)
      throws IOException

Throws:

IOException

loadForWrite

OCacheEntry loadForWrite(long fileId,
 long pageIndex,
 OWriteCache writeCache,
 boolean verifyChecksums,
 OLogSequenceNumber startLSN)
                  throws IOException

Throws:

IOException

loadForRead

OCacheEntry loadForRead(long fileId,
 long pageIndex,
 OWriteCache writeCache,
 boolean verifyChecksums)
                 throws IOException

Throws:

IOException

silentLoadForRead

OCacheEntry silentLoadForRead(long extFileId,
 int pageIndex,
 OWriteCache writeCache,
 boolean verifyChecksums)

releaseFromRead

void releaseFromRead(OCacheEntry cacheEntry)

releaseFromWrite

void releaseFromWrite(OCacheEntry cacheEntry,
 OWriteCache writeCache,
 boolean changed)

allocateNewPage

OCacheEntry allocateNewPage(long fileId,
 OWriteCache writeCache,
 OLogSequenceNumber startLSN)
                     throws IOException

Throws:

IOException

getUsedMemory

long getUsedMemory()

clear

void clear()

truncateFile

void truncateFile(long fileId,
 OWriteCache writeCache)
           throws IOException

Throws:

IOException

closeFile

void closeFile(long fileId,
 boolean flush,
 OWriteCache writeCache)

deleteFile

void deleteFile(long fileId,
 OWriteCache writeCache)
         throws IOException

Throws:

IOException

deleteStorage

void deleteStorage(OWriteCache writeCache)
            throws IOException

Throws:

IOException

closeStorage

void closeStorage(OWriteCache writeCache)
           throws IOException

Closes all files inside of write cache and flushes all associated data.

Parameters:

writeCache - Write cache to close.

Throws:

IOException

changeMaximumAmountOfMemory

void changeMaximumAmountOfMemory(long calculateReadCacheMaxMemory)