Package org.eclipse.rdf4j.sail.nativerdf.btree

Class BTree

java.lang.Object

org.eclipse.rdf4j.sail.nativerdf.btree.BTree

All Implemented Interfaces:

Closeable, AutoCloseable

public class BTree
extends Object
implements Closeable

Implementation of an on-disk B-Tree using the java.nio classes that are available in JDK 1.4 and newer. Documentation about B-Trees can be found on-line at the following URLs:

• http://cis.stvincent.edu/swd/btree/btree.html
,
• http://bluerwhite.org/btree/
, and
• http://semaphorecorp.com/btp/algo.html
.

The first reference was used to implement this class.

Author:

Arjohn Kampman, Enrico Minack

Constructor Summary

Constructors

Constructor	Description
BTree(File dataDir, String filenamePrefix, int blockSize, int valueSize)	Creates a new BTree that uses an instance of DefaultRecordComparator to compare values.
BTree(File dataDir, String filenamePrefix, int blockSize, int valueSize, boolean forceSync)	Creates a new BTree that uses an instance of DefaultRecordComparator to compare values.
BTree(File dataDir, String filenamePrefix, int blockSize, int valueSize, RecordComparator comparator)	Creates a new BTree that uses the supplied RecordComparator to compare the values that are or will be stored in the B-Tree.
BTree(File dataDir, String filenamePrefix, int blockSize, int valueSize, RecordComparator comparator, boolean forceSync)	Creates a new BTree that uses the supplied RecordComparator to compare the values that are or will be stored in the B-Tree.

Method Summary

Modifier and Type	Method	Description
void	clear()	Removes all values from the B-Tree.
void	close()	Closes any opened files and release any resources used by this B-Tree.
boolean	delete()	Closes the BTree and then deletes its data files.
byte[]	get(byte[] key)	Gets the value that matches the specified key.
File	getFile()	Gets the file that this BTree operates on.
long	getValueCountEstimate()	Returns an estimate for the number of values stored in this BTree.
long	getValueCountEstimate(byte[] minValue, byte[] maxValue)	Gives an estimate of the number of values between minValue and maxValue.
byte[]	insert(byte[] value)	Inserts the supplied value into the B-Tree.
RecordIterator	iterateAll()	Returns an iterator that iterates over all values in this B-Tree.
RecordIterator	iterateRange(byte[] minValue, byte[] maxValue)	Returns an iterator that iterates over all values between minValue and maxValue, inclusive.
RecordIterator	iterateRangedValues(byte[] searchKey, byte[] searchMask, byte[] minValue, byte[] maxValue)	Returns an iterator that iterates over all values between minValue and maxValue (inclusive) and returns the values that match the supplied searchKey after searchMask has been applied to the value.
RecordIterator	iterateValues(byte[] searchKey, byte[] searchMask)	Returns an iterator that iterates over all values and returns the values that match the supplied searchKey after searchMask has been applied to the value.
void	print(PrintStream out)
byte[]	remove(byte[] key)	Removes the value that matches the specified key from the B-Tree.
void	sync()	Writes any changes that are cached in memory to disk.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Details

BTree

public BTree(File dataDir,
 String filenamePrefix,
 int blockSize,
 int valueSize)
      throws IOException

Creates a new BTree that uses an instance of DefaultRecordComparator to compare values.

Parameters:

dataDir - The directory for the BTree data.

filenamePrefix - The prefix for all files used by this BTree.

blockSize - The size (in bytes) of a file block for a single node. Ideally, the size specified is the size of a block in the used file system.

valueSize - The size (in bytes) of the fixed-length values that are or will be stored in the B-Tree.

Throws:

IOException - In case the initialization of the B-Tree file failed.

See Also:

• DefaultRecordComparator

BTree

public BTree(File dataDir,
 String filenamePrefix,
 int blockSize,
 int valueSize,
 boolean forceSync)
      throws IOException

Creates a new BTree that uses an instance of DefaultRecordComparator to compare values.

Parameters:

dataDir - The directory for the BTree data.

filenamePrefix - The prefix for all files used by this BTree.

blockSize - The size (in bytes) of a file block for a single node. Ideally, the size specified is the size of a block in the used file system.

valueSize - The size (in bytes) of the fixed-length values that are or will be stored in the B-Tree.

forceSync - Flag indicating whether updates should be synced to disk forcefully by calling FileChannel.force(boolean). This may have a severe impact on write performance.

Throws:

IOException - In case the initialization of the B-Tree file failed.

See Also:

• DefaultRecordComparator

BTree

public BTree(File dataDir,
 String filenamePrefix,
 int blockSize,
 int valueSize,
 RecordComparator comparator)
      throws IOException

Creates a new BTree that uses the supplied RecordComparator to compare the values that are or will be stored in the B-Tree.

Parameters:

dataDir - The directory for the BTree data.

filenamePrefix - The prefix for all files used by this BTree.

blockSize - The size (in bytes) of a file block for a single node. Ideally, the size specified is the size of a block in the used file system.

valueSize - The size (in bytes) of the fixed-length values that are or will be stored in the B-Tree.

comparator - The RecordComparator to use for determining whether one value is smaller, larger or equal to another.

Throws:

IOException - In case the initialization of the B-Tree file failed.

BTree

public BTree(File dataDir,
 String filenamePrefix,
 int blockSize,
 int valueSize,
 RecordComparator comparator,
 boolean forceSync)
      throws IOException

Creates a new BTree that uses the supplied RecordComparator to compare the values that are or will be stored in the B-Tree.

Parameters:

dataDir - The directory for the BTree data.

filenamePrefix - The prefix for all files used by this BTree.

blockSize - The size (in bytes) of a file block for a single node. Ideally, the size specified is the size of a block in the used file system.

valueSize - The size (in bytes) of the fixed-length values that are or will be stored in the B-Tree.

comparator - The RecordComparator to use for determining whether one value is smaller, larger or equal to another.

forceSync - Flag indicating whether updates should be synced to disk forcefully by calling FileChannel.force(boolean). This may have a severe impact on write performance.

Throws:

IOException - In case the initialization of the B-Tree file failed.

Method Details

getFile

public File getFile()

Gets the file that this BTree operates on.

delete

public boolean delete()
               throws IOException

Closes the BTree and then deletes its data files.

Returns:

true if the operation was successful.

Throws:

IOException

close

public void close()
           throws IOException

Closes any opened files and release any resources used by this B-Tree. Any pending changes will be synchronized to disk before closing. Once the B-Tree has been closed, it can no longer be used.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException

sync

public void sync()
          throws IOException

Writes any changes that are cached in memory to disk.

Throws:

IOException

get

public byte[] get(byte[] key)
           throws IOException

Gets the value that matches the specified key.

Parameters:

key - A value that is equal to the value that should be retrieved, at least as far as the RecordComparator of this BTree is concerned.

Returns:

The value matching the key, or null if no such value could be found.

Throws:

IOException

iterateAll

public RecordIterator iterateAll()

Returns an iterator that iterates over all values in this B-Tree.

iterateRange

public RecordIterator iterateRange(byte[] minValue,
 byte[] maxValue)

Returns an iterator that iterates over all values between minValue and maxValue, inclusive.

iterateValues

public RecordIterator iterateValues(byte[] searchKey,
 byte[] searchMask)

Returns an iterator that iterates over all values and returns the values that match the supplied searchKey after searchMask has been applied to the value.

iterateRangedValues

public RecordIterator iterateRangedValues(byte[] searchKey,
 byte[] searchMask,
 byte[] minValue,
 byte[] maxValue)

Returns an iterator that iterates over all values between minValue and maxValue (inclusive) and returns the values that match the supplied searchKey after searchMask has been applied to the value.

getValueCountEstimate

public long getValueCountEstimate()
                           throws IOException

Returns an estimate for the number of values stored in this BTree.

Throws:

IOException

getValueCountEstimate

public long getValueCountEstimate(byte[] minValue,
 byte[] maxValue)
                           throws IOException

Gives an estimate of the number of values between minValue and maxValue.

Parameters:

minValue - the lower bound of the range.

maxValue - the upper bound of the range,

Returns:

an estimate of the number of values in the specified range.

Throws:

IOException

insert

public byte[] insert(byte[] value)
              throws IOException

Inserts the supplied value into the B-Tree. In case an equal value is already present in the B-Tree this value is overwritten with the new value and the old value is returned by this method.

Parameters:

value - The value to insert into the B-Tree.

Returns:

The old value that was replaced, if any.

Throws:

IOException - If an I/O error occurred.

remove

public byte[] remove(byte[] key)
              throws IOException

Removes the value that matches the specified key from the B-Tree.

Parameters:

key - A key that matches the value that should be removed from the B-Tree.

Returns:

The value that was removed from the B-Tree, or null if no matching value was found.

Throws:

IOException - If an I/O error occurred.

clear

public void clear()
           throws IOException

Removes all values from the B-Tree.

Throws:

IOException - If an I/O error occurred.

print

public void print(PrintStream out)
           throws IOException

Throws:

IOException

toString

public String toString()

Overrides:

toString in class Object