org.h2.mvstore
Class MVMap<K,V>

java.lang.Object
  java.util.AbstractMap<K,V>
      org.h2.mvstore.MVMap<K,V>

Type Parameters:

K - the key class

V - the value class

All Implemented Interfaces:

java.util.concurrent.ConcurrentMap<K,V>, java.util.Map<K,V>

Direct Known Subclasses:

MVMapConcurrent, MVRTreeMap, SequenceMap

public class MVMap<K,V>
extends java.util.AbstractMap<K,V>
implements java.util.concurrent.ConcurrentMap<K,V>

A stored map.

Read operations can happen concurrently with all other operations, without risk of corruption.

Write operations first read the relevant area from disk to memory concurrently, and only then modify the data. The in-memory part of write operations is synchronized. For scalable concurrent in-memory write operations, the map should be split into multiple smaller sub-maps that are then synchronized independently.

Nested Class Summary

static class	MVMap.Builder<K,V> A builder for this class.
static interface	MVMap.MapBuilder<M extends MVMap<K,V>,K,V> A builder for maps.

Nested classes/interfaces inherited from class java.util.AbstractMap

java.util.AbstractMap.SimpleEntry<K,V>, java.util.AbstractMap.SimpleImmutableEntry<K,V>

Nested classes/interfaces inherited from interface java.util.Map

java.util.Map.Entry<K,V>

Field Summary

protected Page	root The current root page (may not be null).
protected MVStore	store The store.
protected long	writeVersion The version used for writing.

Constructor Summary

protected

MVMap(DataType keyType, DataType valueType)

Method Summary

boolean	areValuesEqual(java.lang.Object a, java.lang.Object b) Check whether the two values are equal.
protected void	beforeWrite() This method is called before writing to the map.
protected java.lang.Object	binarySearch(Page p, java.lang.Object key) Get the value for the given key, or null if not found.
protected Page	binarySearchPage(Page p, java.lang.Object key) Get the value for the given key, or null if not found.
K	ceilingKey(K key) Get the smallest key that is larger or equal to this key.
void	clear() Remove all entries.
boolean	containsKey(java.lang.Object key)
Cursor<K,V>	cursor(K from) Get a cursor to iterate over a number of keys and values.
java.util.Set<java.util.Map.Entry<K,V>>	entrySet()
boolean	equals(java.lang.Object o)
K	firstKey() Get the first key, or null if the map is empty.
K	floorKey(K key) Get the largest key that is smaller or equal to this key.
V	get(java.lang.Object key) Get a value.
protected int	getChildPageCount(Page p) Get the child page count for this page.
long	getCreateVersion()
protected K	getFirstLast(boolean first) Get the first (lowest) or last (largest) key.
int	getId() Get the map id.
K	getKey(long index) Get the key at the given index.
long	getKeyIndex(K key) Get the index of the given key in the map.
DataType	getKeyType() Get the key type.
protected K	getMinMax(K key, boolean min, boolean excluding) Get the smallest or largest key using the given bounds.
java.lang.String	getName() Get the map name.
Page	getRoot() Get the root page.
MVStore	getStore()
java.lang.String	getType() Get the map type.
DataType	getValueType() Get the value type.
long	getVersion()
int	hashCode()
K	higherKey(K key) Get the smallest key that is larger than the given key, or null if no such key exists.
protected void	init(MVStore store, java.util.HashMap<java.lang.String,java.lang.Object> config) Open this map with the given store and configuration.
boolean	isClosed()
boolean	isEmpty()
boolean	isReadOnly()
boolean	isVolatile() Whether this is volatile map, meaning that changes are not persisted.
java.util.Iterator<K>	keyIterator(K from) Iterate over a number of keys.
java.util.List<K>	keyList() Get the key list.
java.util.Set<K>	keySet()
K	lastKey() Get the last key, or null if the map is empty.
K	lowerKey(K key) Get the largest key that is smaller than the given key, or null if no such key exists.
protected void	newRoot(Page newRoot) Use the new root page from now on.
MVMap<K,V>	openVersion(long version) Open an old version for the given map.
V	put(K key, V value) Add or replace a key-value pair.
protected java.lang.Object	put(Page p, long writeVersion, java.lang.Object key, java.lang.Object value) Add or update a key-value pair.
V	putIfAbsent(K key, V value) Add a key-value pair if it does not yet exist.
V	remove(java.lang.Object key) Remove a key-value pair, if the key exists.
boolean	remove(java.lang.Object key, java.lang.Object value) Remove a key-value pair if the value matches the stored one.
protected java.lang.Object	remove(Page p, long writeVersion, java.lang.Object key) Remove a key-value pair.
protected void	removePage(long pos, int memory) Remove the given page (make the space available).
V	replace(K key, V value) Replace a value for an existing key.
boolean	replace(K key, V oldValue, V newValue) Replace a value for an existing key, if the value matches.
void	setVolatile(boolean isVolatile) Set the volatile flag of the map.
int	size() Get the number of entries, as a integer.
long	sizeAsLong() Get the number of entries, as a long.
protected Page	splitRootIfNeeded(Page p, long writeVersion) Split the root page if necessary.
java.lang.String	toString()

Methods inherited from class java.util.AbstractMap

clone, containsValue, putAll, values

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

containsValue, putAll, values

Field Detail

store

protected MVStore store

The store.

root

protected volatile Page root

The current root page (may not be null).

writeVersion

protected volatile long writeVersion

The version used for writing.

Constructor Detail

MVMap

protected MVMap(DataType keyType,
                DataType valueType)

Method Detail

init

protected void init(MVStore store,
                    java.util.HashMap<java.lang.String,java.lang.Object> config)

Open this map with the given store and configuration.

Parameters:

store - the store

config - the configuration

put

public V put(K key,
             V value)

Add or replace a key-value pair.

Specified by:

put in interface java.util.Map<K,V>

Overrides:

put in class java.util.AbstractMap<K,V>

Parameters:

key - the key (may not be null)

value - the value (may not be null)

Returns:

the old value if the key existed, or null otherwise

splitRootIfNeeded

protected Page splitRootIfNeeded(Page p,
                                 long writeVersion)

Split the root page if necessary.

Parameters:

p - the page

writeVersion - the write version

Returns:

the new sibling

put

protected java.lang.Object put(Page p,
                               long writeVersion,
                               java.lang.Object key,
                               java.lang.Object value)

Add or update a key-value pair.

Parameters:

p - the page

writeVersion - the write version

key - the key (may not be null)

value - the value (may not be null)

Returns:

the old value, or null

firstKey

public K firstKey()

Get the first key, or null if the map is empty.

Returns:

the first key, or null

lastKey

public K lastKey()

Get the last key, or null if the map is empty.

Returns:

the last key, or null

getKey

public K getKey(long index)

Get the key at the given index.

This is a O(log(size)) operation.

Parameters:

index - the index

Returns:

the key

keyList

public java.util.List<K> keyList()

Get the key list. The list is a read-only representation of all keys.

The get and indexOf methods are O(log(size)) operations. The result of indexOf is cast to an int.

Returns:

the key list

getKeyIndex

public long getKeyIndex(K key)

Get the index of the given key in the map.

This is a O(log(size)) operation.

If the key was found, the returned value is the index in the key array. If not found, the returned value is negative, where -1 means the provided key is smaller than any keys. See also Arrays.binarySearch.

Parameters:

key - the key

Returns:

the index

getFirstLast

protected K getFirstLast(boolean first)

Get the first (lowest) or last (largest) key.

Parameters:

first - whether to retrieve the first key

Returns:

the key, or null if the map is empty

higherKey

public K higherKey(K key)

Get the smallest key that is larger than the given key, or null if no such key exists.

Parameters:

key - the key

Returns:

the result

ceilingKey

public K ceilingKey(K key)

Get the smallest key that is larger or equal to this key.

Parameters:

key - the key

Returns:

the result

floorKey

public K floorKey(K key)

Get the largest key that is smaller or equal to this key.

Parameters:

key - the key

Returns:

the result

lowerKey

public K lowerKey(K key)

Get the largest key that is smaller than the given key, or null if no such key exists.

Parameters:

key - the key

Returns:

the result

getMinMax

protected K getMinMax(K key,
                      boolean min,
                      boolean excluding)

Get the smallest or largest key using the given bounds.

Parameters:

key - the key

min - whether to retrieve the smallest key

excluding - if the given upper/lower bound is exclusive

Returns:

the key, or null if no such key exists

get

public V get(java.lang.Object key)

Get a value.

Specified by:

get in interface java.util.Map<K,V>

Overrides:

get in class java.util.AbstractMap<K,V>

Parameters:

key - the key

Returns:

the value, or null if not found

binarySearch

protected java.lang.Object binarySearch(Page p,
                                        java.lang.Object key)

Get the value for the given key, or null if not found.

Parameters:

p - the page

key - the key

Returns:

the value or null

containsKey

public boolean containsKey(java.lang.Object key)

Specified by:

containsKey in interface java.util.Map<K,V>

Overrides:

containsKey in class java.util.AbstractMap<K,V>

binarySearchPage

protected Page binarySearchPage(Page p,
                                java.lang.Object key)

Get the value for the given key, or null if not found.

Parameters:

p - the parent page

key - the key

Returns:

the page or null

clear

public void clear()

Remove all entries.

Specified by:

clear in interface java.util.Map<K,V>

Overrides:

clear in class java.util.AbstractMap<K,V>

isClosed

public boolean isClosed()

remove

public V remove(java.lang.Object key)

Remove a key-value pair, if the key exists.

Specified by:

remove in interface java.util.Map<K,V>

Overrides:

remove in class java.util.AbstractMap<K,V>

Parameters:

key - the key (may not be null)

Returns:

the old value if the key existed, or null otherwise

putIfAbsent

public V putIfAbsent(K key,
                     V value)

Add a key-value pair if it does not yet exist.

Specified by:

putIfAbsent in interface java.util.concurrent.ConcurrentMap<K,V>

Parameters:

key - the key (may not be null)

value - the new value

Returns:

the old value if the key existed, or null otherwise

remove

public boolean remove(java.lang.Object key,
                      java.lang.Object value)

Remove a key-value pair if the value matches the stored one.

Specified by:

remove in interface java.util.concurrent.ConcurrentMap<K,V>

Parameters:

key - the key (may not be null)

value - the expected value

Returns:

true if the item was removed

areValuesEqual

public boolean areValuesEqual(java.lang.Object a,
                              java.lang.Object b)

Check whether the two values are equal.

Parameters:

a - the first value

b - the second value

Returns:

true if they are equal

replace

public boolean replace(K key,
                       V oldValue,
                       V newValue)

Replace a value for an existing key, if the value matches.

Specified by:

replace in interface java.util.concurrent.ConcurrentMap<K,V>

Parameters:

key - the key (may not be null)

oldValue - the expected value

newValue - the new value

Returns:

true if the value was replaced

replace

public V replace(K key,
                 V value)

Replace a value for an existing key.

Specified by:

replace in interface java.util.concurrent.ConcurrentMap<K,V>

Parameters:

key - the key (may not be null)

value - the new value

Returns:

the old value, if the value was replaced, or null

remove

protected java.lang.Object remove(Page p,
                                  long writeVersion,
                                  java.lang.Object key)

Remove a key-value pair.

Parameters:

p - the page (may not be null)

writeVersion - the write version

key - the key

Returns:

the old value, or null if the key did not exist

newRoot

protected void newRoot(Page newRoot)

Use the new root page from now on.

Parameters:

newRoot - the new root page

getKeyType

public DataType getKeyType()

Get the key type.

Returns:

the key type

getValueType

public DataType getValueType()

Get the value type.

Returns:

the value type

keyIterator

public java.util.Iterator<K> keyIterator(K from)

Iterate over a number of keys.

Parameters:

from - the first key to return

Returns:

the iterator

cursor

public Cursor<K,V> cursor(K from)

Get a cursor to iterate over a number of keys and values.

Parameters:

from - the first key to return

Returns:

the cursor

entrySet

public java.util.Set<java.util.Map.Entry<K,V>> entrySet()

Specified by:

entrySet in interface java.util.Map<K,V>

Specified by:

entrySet in class java.util.AbstractMap<K,V>

keySet

public java.util.Set<K> keySet()

Specified by:

keySet in interface java.util.Map<K,V>

Overrides:

keySet in class java.util.AbstractMap<K,V>

getRoot

public Page getRoot()

Get the root page.

Returns:

the root page

getName

public java.lang.String getName()

Get the map name.

Returns:

the name

getStore

public MVStore getStore()

getId

public int getId()

Get the map id. Please note the map id may be different after compacting a store.

Returns:

the map id

isReadOnly

public boolean isReadOnly()

setVolatile

public void setVolatile(boolean isVolatile)

Set the volatile flag of the map.

Parameters:

isVolatile - the volatile flag

isVolatile

public boolean isVolatile()

Whether this is volatile map, meaning that changes are not persisted. By default (even if the store is not persisted), maps are not volatile.

Returns:

whether this map is volatile

beforeWrite

protected void beforeWrite()

This method is called before writing to the map. The default implementation checks whether writing is allowed, and tries to detect concurrent modification.

Throws:

java.lang.UnsupportedOperationException - if the map is read-only, or if another thread is concurrently writing

hashCode

public int hashCode()

Specified by:

hashCode in interface java.util.Map<K,V>

Overrides:

hashCode in class java.util.AbstractMap<K,V>

equals

public boolean equals(java.lang.Object o)

Specified by:

equals in interface java.util.Map<K,V>

Overrides:

equals in class java.util.AbstractMap<K,V>

size

public int size()

Get the number of entries, as a integer. Integer.MAX_VALUE is returned if there are more than this entries.

Specified by:

size in interface java.util.Map<K,V>

Overrides:

size in class java.util.AbstractMap<K,V>

Returns:

the number of entries, as an integer

sizeAsLong

public long sizeAsLong()

Get the number of entries, as a long.

Returns:

the number of entries

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface java.util.Map<K,V>

Overrides:

isEmpty in class java.util.AbstractMap<K,V>

getCreateVersion

public long getCreateVersion()

removePage

protected void removePage(long pos,
                          int memory)

Remove the given page (make the space available).

Parameters:

pos - the position of the page to remove

memory - the number of bytes used for this page

openVersion

public MVMap<K,V> openVersion(long version)

Open an old version for the given map.

Parameters:

version - the version

Returns:

the map

getVersion

public long getVersion()

getChildPageCount

protected int getChildPageCount(Page p)

Get the child page count for this page. This is to allow another map implementation to override the default, in case the last child is not to be used.

Parameters:

p - the page

Returns:

the number of direct children

getType

public java.lang.String getType()

Get the map type. When opening an existing map, the map type must match.

Returns:

the map type

toString

public java.lang.String toString()

Overrides:

toString in class java.util.AbstractMap<K,V>