org.mapdb

Class BTreeKeySerializer<KEY,KEYS>

java.lang.Object

org.mapdb.BTreeKeySerializer<KEY,KEYS>

Type Parameters:

KEY - type of key

KEYS - type of object which holds multiple keys (

Direct Known Subclasses:

BTreeKeySerializer.ArrayKeySerializer, BTreeKeySerializer.BasicKeySerializer, BTreeKeySerializer.Compress

public abstract class BTreeKeySerializer<KEY,KEYS>
extends Object

Custom serializer for BTreeMap keys which enables [Delta encoding](https://en.wikipedia.org/wiki/Delta_encoding). Keys in BTree Nodes are sorted, this enables number of tricks to save disk space. For example for numbers we may store only difference between subsequent numbers, for string we can only take suffix, etc...

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	BTreeKeySerializer.ArrayKeySerializer
static class	BTreeKeySerializer.BasicKeySerializer Basic Key Serializer which just writes data without applying any compression.
static class	BTreeKeySerializer.ByteArrayKeys
static class	BTreeKeySerializer.CharArrayKeys
static class	BTreeKeySerializer.Compress
static interface	BTreeKeySerializer.StringArrayKeys

Field Summary

Fields

Modifier and Type	Field and Description
static BTreeKeySerializer	ARRAY2
static BTreeKeySerializer	ARRAY3
static BTreeKeySerializer	ARRAY4
static BTreeKeySerializer<Object,Object[]>	BASIC
static BTreeKeySerializer<byte[],BTreeKeySerializer.ByteArrayKeys>	BYTE_ARRAY
static BTreeKeySerializer<byte[],byte[][]>	BYTE_ARRAY2
static BTreeKeySerializer<Integer,int[]>	INTEGER Applies delta packing on java.lang.Integer.
static BTreeKeySerializer<Long,long[]>	LONG Applies delta packing on java.lang.Long.
static BTreeKeySerializer<String,BTreeKeySerializer.StringArrayKeys>	STRING
static BTreeKeySerializer<String,char[][]>	STRING2
static BTreeKeySerializer<UUID,long[]>	UUID
static BTreeKeySerializer	ZERO_OR_POSITIVE_INT Deprecated. use INTEGER
static BTreeKeySerializer	ZERO_OR_POSITIVE_LONG Deprecated. use LONG

Constructor Summary

Constructors

Constructor and Description
BTreeKeySerializer()

Method Summary

Methods

Modifier and Type	Method and Description
abstract KEYS	arrayToKeys(Object[] keys)
protected static int	commonPrefixLen(byte[][] bytes)
protected static int	commonPrefixLen(char[][] chars)
abstract Comparator<KEY>	comparator()
abstract int	compare(KEYS keys, int pos1, int pos2)
abstract int	compare(KEYS keys, int pos, KEY key)
boolean	compareIsSmaller(KEYS keys, int pos, KEY key)
abstract KEYS	copyOfRange(KEYS keys, int from, int to)
abstract KEYS	deleteKey(KEYS keys, int pos)
abstract KEYS	deserialize(DataInput in, int nodeSize) Deserializes keys for single BTree Node.
abstract KEYS	emptyKeys()
int	findChildren(BTreeMap.BNode node, Object key) Find the first children node with a key equal or greater than the given key.
int	findChildren2(BTreeMap.BNode node, Object key)
abstract KEY	getKey(KEYS keys, int pos)
boolean	isTrusted()
Object[]	keysToArray(KEYS keys)
abstract int	length(KEYS keys)
abstract KEYS	putKey(KEYS keys, int pos, KEY newKey) expand keys array by one and put newKey at position pos
abstract void	serialize(DataOutput out, KEYS keys) Serialize keys from single BTree Node.

Methods inherited from class java.lang.Object

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

Field Detail

BASIC

public static final BTreeKeySerializer<Object,Object[]> BASIC

LONG

public static final BTreeKeySerializer<Long,long[]> LONG

Applies delta packing on java.lang.Long. Difference between consequential numbers is also packed itself, so for small diffs it takes only single byte per number.

ZERO_OR_POSITIVE_LONG

public static final BTreeKeySerializer ZERO_OR_POSITIVE_LONG

Deprecated. use LONG

INTEGER

public static final BTreeKeySerializer<Integer,int[]> INTEGER

Applies delta packing on java.lang.Integer. Difference between consequential numbers is also packed itself, so for small diffs it takes only single byte per number.

ZERO_OR_POSITIVE_INT

public static final BTreeKeySerializer ZERO_OR_POSITIVE_INT

Deprecated. use INTEGER

ARRAY2

public static final BTreeKeySerializer ARRAY2

ARRAY3

public static final BTreeKeySerializer ARRAY3

ARRAY4

public static final BTreeKeySerializer ARRAY4

UUID

public static final BTreeKeySerializer<UUID,long[]> UUID

STRING2

public static final BTreeKeySerializer<String,char[][]> STRING2

STRING

public static final BTreeKeySerializer<String,BTreeKeySerializer.StringArrayKeys> STRING

BYTE_ARRAY2

public static final BTreeKeySerializer<byte[],byte[][]> BYTE_ARRAY2

BYTE_ARRAY

public static final BTreeKeySerializer<byte[],BTreeKeySerializer.ByteArrayKeys> BYTE_ARRAY

Constructor Detail

BTreeKeySerializer

public BTreeKeySerializer()

Method Detail

serialize

public abstract void serialize(DataOutput out,
             KEYS keys)
                        throws IOException

Serialize keys from single BTree Node.

Parameters:

out - output stream where to put ata

keys - An object which represents keys

Throws:

IOException - in case of an writting error

deserialize

public abstract KEYS deserialize(DataInput in,
               int nodeSize)
                          throws IOException

Deserializes keys for single BTree Node. To

Parameters:

in - input stream to read data from

nodeSize - number of keys in deserialized node

Returns:

an object which represents keys

Throws:

IOException - in case of an reading error

compare

public abstract int compare(KEYS keys,
          int pos1,
          int pos2)

compare

public abstract int compare(KEYS keys,
          int pos,
          KEY key)

compareIsSmaller

public boolean compareIsSmaller(KEYS keys,
                       int pos,
                       KEY key)

getKey

public abstract KEY getKey(KEYS keys,
         int pos)

comparator

public abstract Comparator<KEY> comparator()

emptyKeys

public abstract KEYS emptyKeys()

length

public abstract int length(KEYS keys)

putKey

public abstract KEYS putKey(KEYS keys,
          int pos,
          KEY newKey)

expand keys array by one and put newKey at position pos

Parameters:

keys - array of keys to put new key into

pos - of new key

newKey - new key to insert

Returns:

array of keys with new key at given position

copyOfRange

public abstract KEYS copyOfRange(KEYS keys,
               int from,
               int to)

deleteKey

public abstract KEYS deleteKey(KEYS keys,
             int pos)

findChildren

public int findChildren(BTreeMap.BNode node,
               Object key)

Find the first children node with a key equal or greater than the given key. If all items are smaller it returns keyser.length(keys)

Parameters:

node - BTree Node to find position in

key - key whose position needs to be find

Returns:

position of key in node

findChildren2

public int findChildren2(BTreeMap.BNode node,
                Object key)

arrayToKeys

public abstract KEYS arrayToKeys(Object[] keys)

keysToArray

public Object[] keysToArray(KEYS keys)

isTrusted

public boolean isTrusted()

commonPrefixLen

protected static int commonPrefixLen(byte[][] bytes)

commonPrefixLen

protected static int commonPrefixLen(char[][] chars)