org.apache.cassandra.dht
Class Murmur3Partitioner

java.lang.Object
  org.apache.cassandra.dht.AbstractPartitioner<LongToken>
      org.apache.cassandra.dht.Murmur3Partitioner

All Implemented Interfaces:

IPartitioner<LongToken>

public class Murmur3Partitioner
extends AbstractPartitioner<LongToken>

This class generates a BigIntegerToken using a Murmur3 hash.

Field Summary

static long	MAXIMUM
static LongToken	MINIMUM

Constructor Summary

Murmur3Partitioner()

Method Summary

DecoratedKey	convertFromDiskFormat(java.nio.ByteBuffer key)
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.
LongToken	getMinimumToken()
LongToken	getRandomToken()
LongToken	getToken(java.nio.ByteBuffer key) Generate the token of a key.
Token.TokenFactory<java.lang.Long>	getTokenFactory()
Token	midpoint(Token lToken, Token rToken) Calculate a Token representing the approximate "middle" of the given range.
boolean	preservesOrder()

Methods inherited from class org.apache.cassandra.dht.AbstractPartitioner

minValue

Methods inherited from class java.lang.Object

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

Field Detail

MINIMUM

public static final LongToken MINIMUM

MAXIMUM

public static final long MAXIMUM

See Also:

Constant Field Values

Constructor Detail

Murmur3Partitioner

public Murmur3Partitioner()

Method Detail

convertFromDiskFormat

public DecoratedKey convertFromDiskFormat(java.nio.ByteBuffer key)

Parameters:

key - On disk representation

Returns:

DecoratedKey object

decorateKey

public DecoratedKey decorateKey(java.nio.ByteBuffer key)

Description copied from interface: IPartitioner

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

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.

Returns:

The approximate midpoint between left and right.

getMinimumToken

public LongToken getMinimumToken()

Returns:

The minimum possible Token in the range that is being partitioned.

getToken

public 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.

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 LongToken getRandomToken()

Returns:

a randomly generated token

preservesOrder

public boolean preservesOrder()

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.

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<java.lang.Long> getTokenFactory()