MVMap

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

Nested Classes
Modifier and Type	Class and Description
`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

Fields
Modifier and Type	Field and Description
`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

Constructors
Modifier Constructor and Description

protected MVMap(DataType keyType, DataType valueType)

Constructors
Modifier	Constructor and Description
`protected`	`MVMap(DataType keyType, DataType valueType)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`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.
`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, int id, long createVersion)` 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.concurrent.ConcurrentMap
compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, replaceAll

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,
                    int id,
                    long createVersion)
```
    Open this map with the given store and configuration.
    
    Parameters:
    
    store - the store
    
    id - map id
    
    createVersion - version in which this map was created
  - 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>
  - 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>
    
    Specified by:
    
    putIfAbsent in interface java.util.Map<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>
    
    Specified by:
    
    remove in interface java.util.Map<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>
    
    Specified by:
    
    replace in interface java.util.Map<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>
    
    Specified by:
    
    replace in interface java.util.Map<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>

Class MVMap<K,V>

Nested Class Summary

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

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

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.util.AbstractMap

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.concurrent.ConcurrentMap

Methods inherited from interface java.util.Map

Field Detail

store

root

writeVersion

Constructor Detail

MVMap

Method Detail

init

put

splitRootIfNeeded

put

firstKey

lastKey

getKey

keyList

getKeyIndex

getFirstLast

higherKey

ceilingKey

floorKey

lowerKey

getMinMax

get

binarySearch

containsKey

clear

isClosed

remove

putIfAbsent

remove

areValuesEqual

replace

replace

remove

newRoot

getKeyType

getValueType

keyIterator

cursor

entrySet

keySet

getRoot

getName

getStore

getId

isReadOnly

setVolatile

isVolatile

beforeWrite

hashCode

equals

size

sizeAsLong

isEmpty

getCreateVersion

removePage

openVersion

getVersion

getChildPageCount

getType

toString