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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.cassandra.dht;
import java.nio.ByteBuffer;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Random;
import org.apache.cassandra.db.DecoratedKey;
import org.apache.cassandra.db.marshal.AbstractType;
import org.apache.cassandra.service.StorageService;
import javax.annotation.Nullable;
public interface IPartitioner
{
static IPartitioner global()
{
return StorageService.instance.getTokenMetadata().partitioner;
}
static void validate(Collection> allBounds)
{
for (AbstractBounds bounds : allBounds)
validate(bounds);
}
static void validate(AbstractBounds bounds)
{
if (global() != bounds.left.getPartitioner())
throw new AssertionError(String.format("Partitioner in bounds serialization. Expected %s, was %s.",
global().getClass().getName(),
bounds.left.getPartitioner().getClass().getName()));
}
/**
* Transform key to object representation of the on-disk format.
*
* @param key the raw, client-facing key
* @return decorated version of key
*/
public DecoratedKey decorateKey(ByteBuffer key);
/**
* Calculate a Token representing the approximate "middle" of the given
* range.
*
* @return The approximate midpoint between left and right.
*/
public Token midpoint(Token left, Token right);
/**
* Calculate a Token which take {@code approximate 0 <= ratioToLeft <= 1} ownership of the given range.
*/
public Token split(Token left, Token right, double ratioToLeft);
/**
* @return 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.)
*/
public Token getMinimumToken();
/**
* The biggest token for this partitioner, unlike getMinimumToken, this token is actually used and users wanting to
* include all tokens need to do getMaximumToken().maxKeyBound()
*
* Not implemented for the ordered partitioners
*/
default Token getMaximumToken()
{
throw new UnsupportedOperationException("If you are using a splitting partitioner, getMaximumToken has to be implemented");
}
/**
* @return 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.)
*/
public Token getToken(ByteBuffer key);
/**
* @return a randomly generated token
*/
public Token getRandomToken();
/**
* @param random instance of Random to use when generating the token
*
* @return a randomly generated token
*/
public Token getRandomToken(Random random);
public Token.TokenFactory getTokenFactory();
/**
* @return True if the implementing class preserves key order in the Tokens
* it generates.
*/
public boolean preservesOrder();
/**
* Calculate the deltas between tokens in the ring in order to compare
* relative sizes.
*
* @param sortedTokens a sorted List of Tokens
* @return the mapping from 'token' to 'percentage of the ring owned by that token'.
*/
public Map describeOwnership(List sortedTokens);
public AbstractType getTokenValidator();
/**
* Abstract type that orders the same way as DecoratedKeys provided by this partitioner.
* Used by secondary indices.
*/
/** @deprecated See CASSANDRA-17698 */
@Deprecated(since = "5.0") // use #partitionOrdering(AbstractType) instead, see CASSANDRA-17698 for details
public AbstractType partitionOrdering();
/**
* Abstract type that orders the same way as DecoratedKeys provided by this partitioner.
* Used by secondary indices.
* @param partitionKeyType partition key type for PartitionerDefinedOrder
*/
default AbstractType partitionOrdering(@Nullable AbstractType partitionKeyType)
{
return partitionOrdering();
}
default Optional splitter()
{
return Optional.empty();
}
default public int getMaxTokenSize()
{
return Integer.MIN_VALUE;
}
}