/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*
*/
package org.apache.directory.mavibot.btree.managed;
import java.io.Closeable;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.util.Comparator;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.locks.ReentrantLock;
import net.sf.ehcache.Cache;
import net.sf.ehcache.config.CacheConfiguration;
import org.apache.directory.mavibot.btree.BTreeHeader;
import org.apache.directory.mavibot.btree.DeleteResult;
import org.apache.directory.mavibot.btree.InsertResult;
import org.apache.directory.mavibot.btree.ModifyResult;
import org.apache.directory.mavibot.btree.NotPresentResult;
import org.apache.directory.mavibot.btree.Page;
import org.apache.directory.mavibot.btree.ParentPos;
import org.apache.directory.mavibot.btree.RemoveResult;
import org.apache.directory.mavibot.btree.SplitResult;
import org.apache.directory.mavibot.btree.Transaction;
import org.apache.directory.mavibot.btree.Tuple;
import org.apache.directory.mavibot.btree.TupleCursor;
import org.apache.directory.mavibot.btree.ValueCursor;
import org.apache.directory.mavibot.btree.exception.KeyNotFoundException;
import org.apache.directory.mavibot.btree.serializer.ElementSerializer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* The B+Tree MVCC data structure.
*
* @param <K> The type for the keys
* @param <V> The type for the stored values
*
* @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
*/
public class BTree<K, V> implements Closeable
{
/** The LoggerFactory used by this class */
protected static final Logger LOG = LoggerFactory.getLogger( BTree.class );
/** The Header for a managed BTree */
private BTreeHeader btreeHeader;
/** Default page size (number of entries per node) */
public static final int DEFAULT_PAGE_SIZE = 16;
/** Default size of the buffer used to write data on disk. Around 1Mb */
public static final int DEFAULT_WRITE_BUFFER_SIZE = 4096 * 250;
/** The default journal name */
public static final String DEFAULT_JOURNAL = "mavibot.log";
/** The default data file suffix */
public static final String DATA_SUFFIX = ".db";
/** The default journal file suffix */
public static final String JOURNAL_SUFFIX = ".log";
/** The current rootPage */
protected volatile Page<K, V> rootPage;
/** The list of read transactions being executed */
private ConcurrentLinkedQueue<Transaction<K, V>> readTransactions;
/** The size of the buffer used to write data in disk */
private int writeBufferSize;
/** The Key serializer used for this tree.*/
private ElementSerializer<K> keySerializer;
/** The Value serializer used for this tree. */
private ElementSerializer<V> valueSerializer;
/** The RecordManager if the BTree is managed */
private RecordManager recordManager;
/** A lock used to protect the write operation against concurrent access */
private ReentrantLock writeLock;
/** The thread responsible for the cleanup of timed out reads */
private Thread readTransactionsThread;
/** Define a default delay for a read transaction. This is 10 seconds */
public static final long DEFAULT_READ_TIMEOUT = 10 * 1000L;
/** The read transaction timeout */
private long readTimeOut = DEFAULT_READ_TIMEOUT;
/** The cache associated with this BTree */
private Cache cache;
/** The cache size, default to 1000 elements */
private int cacheSize = DEFAULT_CACHE_SIZE;
/** The default number of pages to keep in memory */
private static final int DEFAULT_CACHE_SIZE = 1000;
/** A flag indicating if this BTree is a Sub BTree */
private boolean isSubBtree = false;
/** The number of stored Values before we switch to a BTree */
private static final int DEFAULT_VALUE_THRESHOLD_UP = 8;
/** The number of stored Values before we switch back to an array */
private static final int DEFAULT_VALUE_THRESHOLD_LOW = 1;
/** The configuration for the array <-> BTree switch */
/*No qualifier*/static int valueThresholdUp = DEFAULT_VALUE_THRESHOLD_UP;
/*No qualifier*/static int valueThresholdLow = DEFAULT_VALUE_THRESHOLD_LOW;
/**
* Create a thread that is responsible of cleaning the transactions when
* they hit the timeout
*/
private void createTransactionManager()
{
Runnable readTransactionTask = new Runnable()
{
public void run()
{
try
{
Transaction<K, V> transaction = null;
while ( !Thread.currentThread().isInterrupted() )
{
long timeoutDate = System.currentTimeMillis() - readTimeOut;
long t0 = System.currentTimeMillis();
int nbTxns = 0;
// Loop on all the transactions from the queue
while ( ( transaction = readTransactions.peek() ) != null )
{
nbTxns++;
if ( transaction.isClosed() )
{
// The transaction is already closed, remove it from the queue
readTransactions.poll();
continue;
}
// Check if the transaction has timed out
if ( transaction.getCreationDate() < timeoutDate )
{
transaction.close();
readTransactions.poll();
continue;
}
// We need to stop now
break;
}
long t1 = System.currentTimeMillis();
if ( nbTxns > 0 )
{
System.out.println( "Processing old txn : " + nbTxns + ", " + ( t1 - t0 ) + "ms" );
}
// Wait until we reach the timeout
Thread.sleep( readTimeOut );
}
}
catch ( InterruptedException ie )
{
//System.out.println( "Interrupted" );
}
catch ( Exception e )
{
throw new RuntimeException( e );
}
}
};
readTransactionsThread = new Thread( readTransactionTask );
readTransactionsThread.setDaemon( true );
readTransactionsThread.start();
}
/**
* Creates a new BTree, with no initialization.
*/
public BTree()
{
btreeHeader = new BTreeHeader();
}
/**
* Creates a new in-memory BTree using the BTreeConfiguration to initialize the
* BTree
*
* @param comparator The comparator to use
*/
public BTree( BTreeConfiguration<K, V> configuration ) throws IOException
{
String name = configuration.getName();
if ( name == null )
{
throw new IllegalArgumentException( "BTree name cannot be null" );
}
btreeHeader = new BTreeHeader();
btreeHeader.setName( name );
btreeHeader.setPageSize( configuration.getPageSize() );
isSubBtree = configuration.isSubBtree();
keySerializer = configuration.getKeySerializer();
btreeHeader.setKeySerializerFQCN( keySerializer.getClass().getName() );
valueSerializer = configuration.getValueSerializer();
btreeHeader.setValueSerializerFQCN( valueSerializer.getClass().getName() );
readTimeOut = configuration.getReadTimeOut();
writeBufferSize = configuration.getWriteBufferSize();
btreeHeader.setAllowDuplicates( configuration.isAllowDuplicates() );
cacheSize = configuration.getCacheSize();
if ( keySerializer.getComparator() == null )
{
throw new IllegalArgumentException( "Comparator should not be null" );
}
// Create the first root page, with revision 0L. It will be empty
// and increment the revision at the same time
rootPage = new Leaf<K, V>( this );
if ( isSubBtree )
{
// The subBTree inherit its cache from its parent BTree
this.cache = configuration.getParentBTree().getCache();
this.writeLock = configuration.getParentBTree().getWriteLock();
readTransactions = new ConcurrentLinkedQueue<Transaction<K, V>>();
}
// Now, initialize the BTree
init();
}
/**
* Creates a new in-memory BTree with a default page size and key/value serializers.
*
* @param comparator The comparator to use
*/
public BTree( String name, ElementSerializer<K> keySerializer, ElementSerializer<V> valueSerializer )
throws IOException
{
this( name, keySerializer, valueSerializer, false );
}
public BTree( String name, ElementSerializer<K> keySerializer, ElementSerializer<V> valueSerializer,
boolean allowDuplicates )
throws IOException
{
this( name, null, keySerializer, valueSerializer, DEFAULT_PAGE_SIZE, allowDuplicates, DEFAULT_CACHE_SIZE );
}
public BTree( String name, ElementSerializer<K> keySerializer, ElementSerializer<V> valueSerializer,
boolean allowDuplicates, int cacheSize )
throws IOException
{
this( name, null, keySerializer, valueSerializer, DEFAULT_PAGE_SIZE, allowDuplicates, cacheSize );
}
/**
* Creates a new in-memory BTree with a default page size and key/value serializers.
*
* @param comparator The comparator to use
*/
public BTree( String name, ElementSerializer<K> keySerializer, ElementSerializer<V> valueSerializer, int pageSize )
throws IOException
{
this( name, null, keySerializer, valueSerializer, pageSize );
}
/**
* Creates a new BTree with a default page size and a comparator, with an associated file.
* @param comparator The comparator to use
* @param serializer The serializer to use
*/
public BTree( String name, String path, ElementSerializer<K> keySerializer, ElementSerializer<V> valueSerializer )
throws IOException
{
this( name, path, keySerializer, valueSerializer, DEFAULT_PAGE_SIZE );
}
/**
*
* Creates a new instance of BTree with the given name and store it under the given dataDir if provided.
*
* @param name the name of the BTree
* @param dataDir the name of the data directory with absolute path
* @param keySerializer key serializer
* @param valueSerializer value serializer
* @param pageSize size of the page
* @throws IOException
*/
public BTree( String name, String dataDir, ElementSerializer<K> keySerializer,
ElementSerializer<V> valueSerializer,
int pageSize )
throws IOException
{
this( name, dataDir, keySerializer, valueSerializer, pageSize, false, DEFAULT_CACHE_SIZE );
}
public BTree( String name, String dataDir, ElementSerializer<K> keySerializer,
ElementSerializer<V> valueSerializer,
int pageSize, boolean allowDuplicates )
throws IOException
{
this( name, dataDir, keySerializer, valueSerializer, pageSize, allowDuplicates, DEFAULT_CACHE_SIZE );
}
public BTree( String name, String dataDir, ElementSerializer<K> keySerializer,
ElementSerializer<V> valueSerializer,
int pageSize, boolean allowDuplicates, int cacheSize )
throws IOException
{
btreeHeader = new BTreeHeader();
btreeHeader.setName( name );
setPageSize( pageSize );
writeBufferSize = DEFAULT_WRITE_BUFFER_SIZE;
this.cacheSize = cacheSize;
this.keySerializer = keySerializer;
btreeHeader.setKeySerializerFQCN( keySerializer.getClass().getName() );
this.valueSerializer = valueSerializer;
btreeHeader.setValueSerializerFQCN( valueSerializer.getClass().getName() );
btreeHeader.setAllowDuplicates( allowDuplicates );
// Create the first root page, with revision 0L. It will be empty
// and increment the revision at the same time
rootPage = new Leaf<K, V>( this );
// Now, call the init() method
init();
}
/**
* Initialize the BTree.
*
* @throws IOException If we get some exception while initializing the BTree
*/
public void init() throws IOException
{
if ( !isSubBtree )
{
// This is not a subBtree, we have to initialize the cache
// Create the queue containing the pending read transactions
readTransactions = new ConcurrentLinkedQueue<Transaction<K, V>>();
writeLock = new ReentrantLock();
// Initialize the caches
CacheConfiguration cacheConfiguration = new CacheConfiguration();
cacheConfiguration.setName( "pages" );
cacheConfiguration.setEternal( true );
cacheConfiguration.setOverflowToDisk( false );
cacheConfiguration.setCacheLoaderTimeoutMillis( 0 );
cacheConfiguration.setMaxElementsInMemory( cacheSize );
cacheConfiguration.setMemoryStoreEvictionPolicy( "LRU" );
cache = new Cache( cacheConfiguration );
cache.initialise();
}
// Initialize the txnManager thread
//FIXME we should NOT create a new transaction manager thread for each BTree
//createTransactionManager();
}
/**
* Return the cache we use in this BTree
*/
/* No qualifier */Cache getCache()
{
return cache;
}
/**
* Return the cache we use in this BTree
*/
/* No qualifier */ReentrantLock getWriteLock()
{
return writeLock;
}
/**
* Return the cache we use in this BTree
*/
/* No qualifier */ConcurrentLinkedQueue<Transaction<K, V>> getReadTransactions()
{
return readTransactions;
}
/**
* Close the BTree, cleaning up all the data structure
*/
public void close() throws IOException
{
// Stop the readTransaction thread
// readTransactionsThread.interrupt();
// readTransactions.clear();
rootPage = null;
}
/**
* @return the btreeOffset
*/
/* No qualifier*/long getBtreeOffset()
{
return btreeHeader.getBTreeOffset();
}
/**
* @param btreeOffset the btreeOffset to set
*/
/* No qualifier*/void setBtreeOffset( long btreeOffset )
{
btreeHeader.setBTreeOffset( btreeOffset );
}
/**
* @return the rootPageOffset
*/
/* No qualifier*/long getRootPageOffset()
{
return btreeHeader.getRootPageOffset();
}
/**
* @param rootPageOffset the rootPageOffset to set
*/
/* No qualifier*/void setRootPageOffset( long rootPageOffset )
{
btreeHeader.setRootPageOffset( rootPageOffset );
}
/**
* @return the nextBTreeOffset
*/
/* No qualifier*/long getNextBTreeOffset()
{
return btreeHeader.getNextBTreeOffset();
}
/**
* @param nextBTreeOffset the nextBTreeOffset to set
*/
/* No qualifier*/void setNextBTreeOffset( long nextBTreeOffset )
{
btreeHeader.setNextBTreeOffset( nextBTreeOffset );
}
/**
* Gets the number which is a power of 2 immediately above the given positive number.
*/
private int getPowerOf2( int size )
{
int newSize = --size;
newSize |= newSize >> 1;
newSize |= newSize >> 2;
newSize |= newSize >> 4;
newSize |= newSize >> 8;
newSize |= newSize >> 16;
newSize++;
return newSize;
}
/**
* Set the maximum number of elements we can store in a page. This must be a
* number greater than 1, and a power of 2. The default page size is 16.
* <br/>
* If the provided size is below 2, we will default to DEFAULT_PAGE_SIZE.<br/>
* If the provided size is not a power of 2, we will select the closest power of 2
* higher than the given number<br/>
*
* @param pageSize The requested page size
*/
public void setPageSize( int pageSize )
{
if ( pageSize <= 2 )
{
btreeHeader.setPageSize( DEFAULT_PAGE_SIZE );
}
else
{
btreeHeader.setPageSize( getPowerOf2( pageSize ) );
}
}
/**
* Set the new root page for this tree. Used for debug purpose only. The revision
* will always be 0;
*
* @param root the new root page.
*/
/* No qualifier */void setRoot( Page<K, V> root )
{
rootPage = root;
}
/**
* Gets the RecordManager for a managed BTree
*
* @return The recordManager if the BTree is managed
*/
/* No qualifier */RecordManager getRecordManager()
{
return recordManager;
}
/**
* Inject a RecordManager for a managed BTree
*
* @param recordManager The injected RecordManager
*/
/* No qualifier */void setRecordManager( RecordManager recordManager )
{
this.recordManager = recordManager;
}
/**
* @return the pageSize
*/
public int getPageSize()
{
return btreeHeader.getPageSize();
}
/**
* Generates a new revision number. It's only used by the Page instances.
*
* @return a new incremental revision number
*/
/** No qualifier */
long generateRevision()
{
return btreeHeader.incrementRevision();
}
/**
* Insert an entry in the BTree.
* <p>
* We will replace the value if the provided key already exists in the
* btree.
*
* @param key Inserted key
* @param value Inserted value
* @return Existing value, if any.
* @throws IOException TODO
*/
public V insert( K key, V value ) throws IOException
{
long revision = generateRevision();
V existingValue = null;
try
{
// Commented atm, we will have to play around the idea of transactions later
writeLock.lock();
InsertResult<K, V> result = insert( key, value, revision );
if ( result instanceof ModifyResult )
{
existingValue = ( ( ModifyResult<K, V> ) result ).getModifiedValue();
}
}
finally
{
// See above
writeLock.unlock();
}
return existingValue;
}
/**
* Delete the entry which key is given as a parameter. If the entry exists, it will
* be removed from the tree, the old tuple will be returned. Otherwise, null is returned.
*
* @param key The key for the entry we try to remove
* @return A Tuple<K, V> containing the removed entry, or null if it's not found.
*/
public Tuple<K, V> delete( K key ) throws IOException
{
if ( key == null )
{
throw new IllegalArgumentException( "Key must not be null" );
}
long revision = generateRevision();
Tuple<K, V> deleted = delete( key, revision );
return deleted;
}
/**
* Delete the value from an entry associated with the given key. If the value
* If the value is present, it will be deleted first, later if there are no other
* values associated with this key(which can happen when duplicates are enabled),
* we will remove the key from the tree.
*
* @param key The key for the entry we try to remove
* @param value The value to delete (can be null)
* @return A Tuple<K, V> containing the removed entry, or null if it's not found.
*/
public Tuple<K, V> delete( K key, V value ) throws IOException
{
if ( key == null )
{
throw new IllegalArgumentException( "Key must not be null" );
}
if ( value == null )
{
throw new IllegalArgumentException( "Value must not be null" );
}
long revision = generateRevision();
Tuple<K, V> deleted = delete( key, value, revision );
return deleted;
}
/**
* Delete the entry which key is given as a parameter. If the entry exists, it will
* be removed from the tree, the old tuple will be returned. Otherwise, null is returned.
*
* @param key The key for the entry we try to remove
* @return A Tuple<K, V> containing the removed entry, or null if it's not found.
*/
private Tuple<K, V> delete( K key, long revision ) throws IOException
{
return delete( key, null, revision );
}
/**
*
* Deletes the given <key,value> pair if both key and value match. If the given value is null
* and there is no null value associated with the given key then the entry with the given key
* will be removed.
*
* @param key The key to be removed
* @param value The value to be removed (can be null, and when no null value exists the key will be removed irrespective of the value)
* @param revision The revision to be associated with this operation
* @return
* @throws IOException
*/
private Tuple<K, V> delete( K key, V value, long revision ) throws IOException
{
writeLock.lock();
try
{
// If the key exists, the existing value will be replaced. We store it
// to return it to the caller.
Tuple<K, V> tuple = null;
// Try to delete the entry starting from the root page. Here, the root
// page may be either a Node or a Leaf
DeleteResult<K, V> result = rootPage.delete( revision, key, value, null, -1 );
if ( result instanceof NotPresentResult )
{
// Key not found.
return null;
}
// Keep the oldRootPage so that we can later access it
Page<K, V> oldRootPage = rootPage;
if ( result instanceof RemoveResult )
{
// The element was found, and removed
RemoveResult<K, V> removeResult = ( RemoveResult<K, V> ) result;
Page<K, V> modifiedPage = removeResult.getModifiedPage();
// Write the modified page on disk
// Note that we don't use the holder, the new root page will
// remain in memory.
PageHolder<K, V> holder = recordManager.writePage( this, modifiedPage,
revision );
// Store the offset on disk in the page in memory
( ( AbstractPage<K, V> ) modifiedPage ).setOffset( ( ( PageHolder<K, V> ) holder )
.getOffset() );
// Store the last offset on disk in the page in memory
( ( AbstractPage<K, V> ) modifiedPage )
.setLastOffset( ( ( PageHolder<K, V> ) holder )
.getLastOffset() );
// This is a new root
rootPage = modifiedPage;
tuple = removeResult.getRemovedElement();
}
// Decrease the number of elements in the current tree if the deletion is successful
if ( tuple != null )
{
btreeHeader.decrementNbElems();
// We have to update the rootPage on disk
// Update the BTree header now
recordManager.updateBtreeHeader( this, ( ( AbstractPage<K, V> ) rootPage ).getOffset() );
}
recordManager.addFreePages( this, result.getCopiedPages() );
// Store the created rootPage into the revision BTree, this will be stored in RecordManager only if revisions are set to keep
recordManager.storeRootPage( this, rootPage );
// Return the value we have found if it was modified
return tuple;
}
finally
{
// See above
writeLock.unlock();
}
}
/**
* Find a value in the tree, given its key. If the key is not found,
* it will throw a KeyNotFoundException. <br/>
* Note that we can get a null value stored, or many values.
*
* @param key The key we are looking at
* @return The found value, or null if the key is not present in the tree
* @throws KeyNotFoundException If the key is not found in the BTree
* @throws IOException TODO
*/
public V get( K key ) throws IOException, KeyNotFoundException
{
return rootPage.get( key );
}
/**
* @see Page#getValues(Object)
*/
public ValueCursor<V> getValues( K key ) throws IOException, KeyNotFoundException
{
return rootPage.getValues( key );
}
/**
* Find a value in the tree, given its key, at a specific revision. If the key is not found,
* it will throw a KeyNotFoundException. <br/>
* Note that we can get a null value stored, or many values.
*
* @param revision The revision for which we want to find a key
* @param key The key we are looking at
* @return The found value, or null if the key is not present in the tree
* @throws KeyNotFoundException If the key is not found in the BTree
* @throws IOException If there was an issue while fetching data from the disk
*/
public V get( long revision, K key ) throws IOException, KeyNotFoundException
{
// Fetch the root page for this revision
Page<K, V> revisionRootPage = getRootPage( revision );
return revisionRootPage.get( key );
}
/**
* Checks if the given key exists.
*
* @param key The key we are looking at
* @return true if the key is present, false otherwise
* @throws IOException If we have an error while trying to access the page
*/
public boolean hasKey( K key ) throws IOException
{
if ( key == null )
{
return false;
}
return rootPage.hasKey( key );
}
/**
* Checks if the given key exists for a given revision.
*
* @param revision The revision for which we want to find a key
* @param key The key we are looking at
* @return true if the key is present, false otherwise
* @throws IOException If we have an error while trying to access the page
* @throws KeyNotFoundException If the key is not found in the BTree
*/
public boolean hasKey( long revision, K key ) throws IOException, KeyNotFoundException
{
if ( key == null )
{
return false;
}
// Fetch the root page for this revision
Page<K, V> revisionRootPage = getRootPage( revision );
return revisionRootPage.hasKey( key );
}
/**
* Checks if the BTree contains the given key with the given value.
*
* @param key The key we are looking for
* @param value The value associated with the given key
* @return true if the key and value are associated with each other, false otherwise
*/
public boolean contains( K key, V value ) throws IOException
{
return rootPage.contains( key, value );
}
/**
* Checks if the BTree contains the given key with the given value for a given revision
*
* @param revision The revision we would like to browse
* @param key The key we are looking for
* @param value The value associated with the given key
* @return true if the key and value are associated with each other, false otherwise
* @throws KeyNotFoundException If the key is not found in the BTree
*/
public boolean contains( long revision, K key, V value ) throws IOException, KeyNotFoundException
{
// Fetch the root page for this revision
Page<K, V> revisionRootPage = getRootPage( revision );
return revisionRootPage.contains( key, value );
}
/**
* Creates a cursor starting at the beginning of the tree
*
* @return A cursor on the btree
* @throws IOException
*/
public TupleCursor<K, V> browse() throws IOException
{
Transaction<K, V> transaction = beginReadTransaction();
// Fetch the root page for this revision
ParentPos<K, V>[] stack = new ParentPos[32];
TupleCursor<K, V> cursor = rootPage.browse( transaction, stack, 0 );
// Set the position before the first element
cursor.beforeFirst();
return cursor;
}
/**
* Creates a cursor starting at the beginning of the tree, for a given revision
*
* @param revision The revision we would like to browse
* @return A cursor on the btree
* @throws IOException If we had an issue while fetching data from the disk
* @throws KeyNotFoundException If the key is not found in the BTree
*/
public TupleCursor<K, V> browse( long revision ) throws IOException, KeyNotFoundException
{
Transaction<K, V> transaction = beginReadTransaction();
// Fetch the root page for this revision
Page<K, V> revisionRootPage = getRootPage( revision );
// And get the cursor
TupleCursor<K, V> cursor = revisionRootPage.browse( transaction, new ParentPos[32], 0 );
return cursor;
}
/**
* Creates a cursor starting on the given key
*
* @param key The key which is the starting point. If the key is not found,
* then the cursor will always return null.
* @return A cursor on the btree
* @throws IOException
*/
public TupleCursor<K, V> browseFrom( K key ) throws IOException
{
Transaction<K, V> transaction = beginReadTransaction();
// Fetch the root page for this revision
@SuppressWarnings("unchecked")
ParentPos<K, V>[] stack = new ParentPos[32];
TupleCursor<K, V> cursor = rootPage.browse( key, transaction, stack, 0 );
return cursor;
}
/**
* Creates a cursor starting on the given key at the given revision
*
* @param The revision we are looking for
* @param key The key which is the starting point. If the key is not found,
* then the cursor will always return null.
* @return A cursor on the btree
* @throws IOException If wxe had an issue reading the BTree from disk
* @throws KeyNotFoundException If we can't find a rootPage for this revision
*/
public TupleCursor<K, V> browseFrom( long revision, K key ) throws IOException, KeyNotFoundException
{
Transaction<K, V> transaction = beginReadTransaction();
// Fetch the rootPage for this revision
Page<K, V> revisionRootPage = getRootPage( revision );
// And get the cursor
TupleCursor<K, V> cursor = revisionRootPage.browse( key, transaction, new ParentPos[32], 0 );
return cursor;
}
/**
* Insert an entry in the BTree.
* <p>
* We will replace the value if the provided key already exists in the
* btree.
* <p>
* The revision number is the revision to use to insert the data.
*
* @param key Inserted key
* @param value Inserted value
* @param revision The revision to use
* @return an instance of the InsertResult.
*/
/*No qualifier*/InsertResult<K, V> insert( K key, V value, long revision ) throws IOException
{
if ( key == null )
{
throw new IllegalArgumentException( "Key must not be null" );
}
// If the key exists, the existing value will be replaced. We store it
// to return it to the caller.
V modifiedValue = null;
// Try to insert the new value in the tree at the right place,
// starting from the root page. Here, the root page may be either
// a Node or a Leaf
InsertResult<K, V> result = rootPage.insert( revision, key, value );
if ( result instanceof ModifyResult )
{
ModifyResult<K, V> modifyResult = ( ( ModifyResult<K, V> ) result );
Page<K, V> modifiedPage = modifyResult.getModifiedPage();
// Write the modified page on disk
// Note that we don't use the holder, the new root page will
// remain in memory.
PageHolder<K, V> holder = recordManager.writePage( this, modifiedPage,
revision );
// The root has just been modified, we haven't split it
// Get it and make it the current root page
rootPage = modifiedPage;
modifiedValue = modifyResult.getModifiedValue();
}
else
{
// We have split the old root, create a new one containing
// only the pivotal we got back
SplitResult<K, V> splitResult = ( ( SplitResult<K, V> ) result );
K pivot = splitResult.getPivot();
Page<K, V> leftPage = splitResult.getLeftPage();
Page<K, V> rightPage = splitResult.getRightPage();
Page<K, V> newRootPage = null;
// If the BTree is managed, we have to write the two pages that were created
// and to keep a track of the two offsets for the upper node
PageHolder<K, V> holderLeft = recordManager.writePage( this,
leftPage, revision );
PageHolder<K, V> holderRight = recordManager.writePage( this,
rightPage, revision );
// Create the new rootPage
newRootPage = new Node<K, V>( this, revision, pivot, holderLeft, holderRight );
// If the BTree is managed, we now have to write the page on disk
// and to add this page to the list of modified pages
PageHolder<K, V> holder = recordManager
.writePage( this, newRootPage, revision );
rootPage = newRootPage;
}
// Increase the number of element in the current tree if the insertion is successful
// and does not replace an element
if ( modifiedValue == null )
{
btreeHeader.incrementNbElems();
}
// If the BTree is managed, we have to update the rootPage on disk
// Update the BTree header now
recordManager.updateBtreeHeader( this, ( ( AbstractPage<K, V> ) rootPage ).getOffset() );
// Moved the free pages into the list of free pages
recordManager.addFreePages( this, result.getCopiedPages() );
// Store the created rootPage into the revision BTree, this will be stored in RecordManager only if revisions are set to keep
recordManager.storeRootPage( this, rootPage );
// Return the value we have found if it was modified
return result;
}
/**
* Starts a Read Only transaction. If the transaction is not closed, it will be
* automatically closed after the timeout
* @return The created transaction
*/
private Transaction<K, V> beginReadTransaction()
{
Transaction<K, V> readTransaction = new Transaction<K, V>( rootPage, btreeHeader.getRevision() - 1,
System.currentTimeMillis() );
readTransactions.add( readTransaction );
return readTransaction;
}
/**
* @return the comparator
*/
public Comparator<K> getComparator()
{
return keySerializer.getComparator();
}
/**
* @param keySerializer the Key serializer to set
*/
public void setKeySerializer( ElementSerializer<K> keySerializer )
{
this.keySerializer = keySerializer;
btreeHeader.setKeySerializerFQCN( keySerializer.getClass().getName() );
}
/**
* @param valueSerializer the Value serializer to set
*/
public void setValueSerializer( ElementSerializer<V> valueSerializer )
{
this.valueSerializer = valueSerializer;
btreeHeader.setValueSerializerFQCN( valueSerializer.getClass().getName() );
}
/**
* Write the data in the ByteBuffer, and eventually on disk if needed.
*
* @param channel The channel we want to write to
* @param bb The ByteBuffer we want to feed
* @param buffer The data to inject
* @throws IOException If the write failed
*/
private void writeBuffer( FileChannel channel, ByteBuffer bb, byte[] buffer ) throws IOException
{
int size = buffer.length;
int pos = 0;
// Loop until we have written all the data
do
{
if ( bb.remaining() >= size )
{
// No flush, as the ByteBuffer is big enough
bb.put( buffer, pos, size );
size = 0;
}
else
{
// Flush the data on disk, reinitialize the ByteBuffer
int len = bb.remaining();
size -= len;
bb.put( buffer, pos, len );
pos += len;
bb.flip();
channel.write( bb );
bb.clear();
}
}
while ( size > 0 );
}
/**
* Get the rootPzge associated to a give revision.
*
* @param revision The revision we are looking for
* @return The rootPage associated to this revision
* @throws IOException If we had an issue while accessing the underlying file
* @throws KeyNotFoundException If the revision does not exist for this Btree
*/
private Page<K, V> getRootPage( long revision ) throws IOException, KeyNotFoundException
{
return recordManager.getRootPage( this, revision );
}
/**
* Flush the latest revision to disk. We will replace the current file by the new one, as
* we flush in a temporary file.
*/
public void flush() throws IOException
{
}
/**
* @return the readTimeOut
*/
public long getReadTimeOut()
{
return readTimeOut;
}
/**
* @param readTimeOut the readTimeOut to set
*/
public void setReadTimeOut( long readTimeOut )
{
this.readTimeOut = readTimeOut;
}
/**
* @return the name
*/
public String getName()
{
return btreeHeader.getName();
}
/**
* @param name the name to set
*/
public void setName( String name )
{
btreeHeader.setName( name );
}
/**
* @return the writeBufferSize
*/
public int getWriteBufferSize()
{
return writeBufferSize;
}
/**
* @param writeBufferSize the writeBufferSize to set
*/
public void setWriteBufferSize( int writeBufferSize )
{
this.writeBufferSize = writeBufferSize;
}
/**
* Create a ValueHolder depending on the kind of holder we want.
*
* @param value The value to store
* @return The value holder
*/
@SuppressWarnings("unchecked")
/* no qualifier */ValueHolder<V> createValueHolder( V value )
{
return new ValueHolder<V>( this, value );
}
/**
* Create a ValueHolder depending on the kind of holder we want.
*
* @param value The value to store
* @return The value holder
*/
/* no qualifier */PageHolder<K, V> createPageHolder( Page<K, V> value )
{
return new PageHolder<K, V>( this, value,
value.getOffset(), value.getLastOffset() );
}
/**
* @return the keySerializer
*/
public ElementSerializer<K> getKeySerializer()
{
return keySerializer;
}
/**
* @return the keySerializer FQCN
*/
public String getKeySerializerFQCN()
{
return btreeHeader.getKeySerializerFQCN();
}
/**
* @return the valueSerializer
*/
public ElementSerializer<V> getValueSerializer()
{
return valueSerializer;
}
/**
* @return the valueSerializer FQCN
*/
public String getValueSerializerFQCN()
{
return btreeHeader.getValueSerializerFQCN();
}
/**
* @return The current BTree revision
*/
public long getRevision()
{
return btreeHeader.getRevision();
}
/**
* @param revision the revision to set
*/
/* No qualifier */void setRevision( long revision )
{
btreeHeader.setRevision( revision );
}
/**
* @return The current number of elements in the BTree
*/
public long getNbElems()
{
return btreeHeader.getNbElems();
}
/**
* @param nbElems the nbElems to set
*/
/* No qualifier */void setNbElems( long nbElems )
{
btreeHeader.setNbElems( nbElems );
}
/**
* @return true if this BTree allow duplicate values
*/
public boolean isAllowDuplicates()
{
return btreeHeader.isAllowDuplicates();
}
/* No qualifier */void setAllowDuplicates( boolean allowDuplicates )
{
btreeHeader.setAllowDuplicates( allowDuplicates );
}
/**
* @see Object#toString()
*/
public String toString()
{
StringBuilder sb = new StringBuilder();
sb.append( "Managed BTree" );
sb.append( "[" ).append( btreeHeader.getName() ).append( "]" );
sb.append( "( pageSize:" ).append( btreeHeader.getPageSize() );
if ( rootPage != null )
{
sb.append( ", nbEntries:" ).append( btreeHeader.getNbElems() );
}
else
{
sb.append( ", nbEntries:" ).append( 0 );
}
sb.append( ", comparator:" );
if ( keySerializer.getComparator() == null )
{
sb.append( "null" );
}
else
{
sb.append( keySerializer.getComparator().getClass().getSimpleName() );
}
sb.append( ", DuplicatesAllowed: " ).append( btreeHeader.isAllowDuplicates() );
sb.append( ") : \n" );
sb.append( rootPage.dumpPage( "" ) );
return sb.toString();
}
}