org.apache.cassandra.dht

Class Murmur3Partitioner

java.lang.Object

org.apache.cassandra.dht.Murmur3Partitioner

All Implemented Interfaces:

IPartitioner

public class Murmur3Partitioner
extends java.lang.Object
implements IPartitioner

This class generates a BigIntegerToken using a Murmur3 hash.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Murmur3Partitioner.LongToken

Field Summary

Fields

Modifier and Type	Field and Description
static Murmur3Partitioner	instance
static long	MAXIMUM
static Murmur3Partitioner.LongToken	MINIMUM

Constructor Summary

Constructors

Constructor and Description
Murmur3Partitioner()

Method Summary

Modifier and Type	Method and Description
DecoratedKey	decorateKey(java.nio.ByteBuffer key) Transform key to object representation of the on-disk format.
java.util.Map<Token,java.lang.Float>	describeOwnership(java.util.List<Token> sortedTokens) Calculate the deltas between tokens in the ring in order to compare relative sizes.
Murmur3Partitioner.LongToken	getMinimumToken()
Murmur3Partitioner.LongToken	getRandomToken()
Murmur3Partitioner.LongToken	getToken(java.nio.ByteBuffer key) Generate the token of a key.
Token.TokenFactory	getTokenFactory()
AbstractType<?>	getTokenValidator()
Token	midpoint(Token lToken, Token rToken) Calculate a Token representing the approximate "middle" of the given range.
boolean	preservesOrder()

Methods inherited from class java.lang.Object

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

Field Detail

MINIMUM

public static final Murmur3Partitioner.LongToken MINIMUM

MAXIMUM

public static final long MAXIMUM

See Also:

Constant Field Values

instance

public static final Murmur3Partitioner instance

Constructor Detail

Murmur3Partitioner

public Murmur3Partitioner()

Method Detail

decorateKey

public DecoratedKey decorateKey(java.nio.ByteBuffer key)

Description copied from interface: IPartitioner

Transform key to object representation of the on-disk format.

Specified by:

decorateKey in interface IPartitioner

Parameters:

key - the raw, client-facing key

Returns:

decorated version of key

midpoint

public Token midpoint(Token lToken,
                      Token rToken)

Description copied from interface: IPartitioner

Calculate a Token representing the approximate "middle" of the given range.

Specified by:

midpoint in interface IPartitioner

Returns:

The approximate midpoint between left and right.

getMinimumToken

public Murmur3Partitioner.LongToken getMinimumToken()

Specified by:

getMinimumToken in interface IPartitioner

Returns:

A Token smaller than all others in the range that is being partitioned. Not legal to assign to a node or key. (But legal to use in range scans.)

getToken

public Murmur3Partitioner.LongToken getToken(java.nio.ByteBuffer key)

Generate the token of a key. Note that we need to ensure all generated token are strictly bigger than MINIMUM. In particular we don't want MINIMUM to correspond to any key because the range (MINIMUM, X] doesn't include MINIMUM but we use such range to select all data whose token is smaller than X.

Specified by:

getToken in interface IPartitioner

Returns:

a Token that can be used to route a given key (This is NOT a method to create a Token from its string representation; for that, use TokenFactory.fromString.)

getRandomToken

public Murmur3Partitioner.LongToken getRandomToken()

Specified by:

getRandomToken in interface IPartitioner

Returns:

a randomly generated token

preservesOrder

public boolean preservesOrder()

Specified by:

preservesOrder in interface IPartitioner

Returns:

True if the implementing class preserves key order in the Tokens it generates.

describeOwnership

public java.util.Map<Token,java.lang.Float> describeOwnership(java.util.List<Token> sortedTokens)

Description copied from interface: IPartitioner

Calculate the deltas between tokens in the ring in order to compare relative sizes.

Specified by:

describeOwnership in interface IPartitioner

Parameters:

sortedTokens - a sorted List of Tokens

Returns:

the mapping from 'token' to 'percentage of the ring owned by that token'.

getTokenFactory

public Token.TokenFactory getTokenFactory()

Specified by:

getTokenFactory in interface IPartitioner

getTokenValidator

public AbstractType<?> getTokenValidator()

Specified by:

getTokenValidator in interface IPartitioner