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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.db;
import java.nio.ByteBuffer;
import java.util.Comparator;
import java.util.List;
import java.util.StringJoiner;
import java.util.function.BiFunction;
import org.apache.cassandra.db.marshal.CompositeType;
import org.apache.cassandra.dht.IPartitioner;
import org.apache.cassandra.dht.Token;
import org.apache.cassandra.dht.Token.KeyBound;
import org.apache.cassandra.schema.ColumnMetadata;
import org.apache.cassandra.schema.TableMetadata;
import org.apache.cassandra.utils.ByteBufferUtil;
import org.apache.cassandra.utils.IFilter.FilterKey;
import org.apache.cassandra.utils.MurmurHash;
import org.apache.cassandra.utils.bytecomparable.ByteComparable;
import org.apache.cassandra.utils.bytecomparable.ByteSource;
import org.apache.cassandra.utils.bytecomparable.ByteSourceInverse;
import org.apache.cassandra.utils.memory.HeapCloner;
/**
* Represents a decorated key, handy for certain operations
* where just working with strings gets slow.
*
* We do a lot of sorting of DecoratedKeys, so for speed, we assume that tokens correspond one-to-one with keys.
* This is not quite correct in the case of RandomPartitioner (which uses MD5 to hash keys to tokens);
* if this matters, you can subclass RP to use a stronger hash, or use a non-lossy tokenization scheme (as in the
* OrderPreservingPartitioner classes).
*/
public abstract class DecoratedKey implements PartitionPosition, FilterKey
{
public static final Comparator comparator = DecoratedKey::compareTo;
private final Token token;
public DecoratedKey(Token token)
{
assert token != null;
this.token = token;
}
@Override
public int hashCode()
{
return getKey().hashCode(); // hash of key is enough
}
@Override
public boolean equals(Object obj)
{
if (this == obj)
return true;
if (obj == null || !(obj instanceof DecoratedKey))
return false;
DecoratedKey other = (DecoratedKey)obj;
return ByteBufferUtil.compareUnsigned(getKey(), other.getKey()) == 0; // we compare faster than BB.equals for array backed BB
}
public int compareTo(PartitionPosition pos)
{
if (this == pos)
return 0;
// delegate to Token.KeyBound if needed
if (!(pos instanceof DecoratedKey))
return -pos.compareTo(this);
DecoratedKey otherKey = (DecoratedKey) pos;
int cmp = getToken().compareTo(otherKey.getToken());
return cmp == 0 ? ByteBufferUtil.compareUnsigned(getKey(), otherKey.getKey()) : cmp;
}
public static int compareTo(IPartitioner partitioner, ByteBuffer key, PartitionPosition position)
{
// delegate to Token.KeyBound if needed
if (!(position instanceof DecoratedKey))
return -position.compareTo(partitioner.decorateKey(key));
DecoratedKey otherKey = (DecoratedKey) position;
int cmp = partitioner.getToken(key).compareTo(otherKey.getToken());
return cmp == 0 ? ByteBufferUtil.compareUnsigned(key, otherKey.getKey()) : cmp;
}
@Override
public ByteSource asComparableBytes(Version version)
{
// Note: In the legacy version one encoding could be a prefix of another as the escaping is only weakly
// prefix-free (see ByteSourceTest.testDecoratedKeyPrefixes()).
// The OSS50 version avoids this by adding a terminator.
return ByteSource.withTerminatorMaybeLegacy(version,
ByteSource.END_OF_STREAM,
token.asComparableBytes(version),
keyComparableBytes(version));
}
@Override
public ByteComparable asComparableBound(boolean before)
{
return version ->
{
assert (version != Version.LEGACY) : "Decorated key bounds are not supported by the legacy encoding.";
return ByteSource.withTerminator(
before ? ByteSource.LT_NEXT_COMPONENT : ByteSource.GT_NEXT_COMPONENT,
token.asComparableBytes(version),
keyComparableBytes(version));
};
}
protected ByteSource keyComparableBytes(Version version)
{
return ByteSource.of(getKey(), version);
}
public IPartitioner getPartitioner()
{
return getToken().getPartitioner();
}
public KeyBound minValue()
{
return getPartitioner().getMinimumToken().minKeyBound();
}
public boolean isMinimum()
{
// A DecoratedKey can never be the minimum position on the ring
return false;
}
public PartitionPosition.Kind kind()
{
return PartitionPosition.Kind.ROW_KEY;
}
@Override
public String toString()
{
String keystring = getKey() == null ? "null" : ByteBufferUtil.bytesToHex(getKey());
return "DecoratedKey(" + getToken() + ", " + keystring + ")";
}
/**
* Returns a CQL representation of this key.
*
* @param metadata the metadata of the table that this key belogs to
* @return a CQL representation of this key
*/
public String toCQLString(TableMetadata metadata)
{
List columns = metadata.partitionKeyColumns();
if (columns.size() == 1)
return toCQLString(columns.get(0), getKey());
ByteBuffer[] values = ((CompositeType) metadata.partitionKeyType).split(getKey());
StringJoiner joiner = new StringJoiner(" AND ");
for (int i = 0; i < columns.size(); i++)
joiner.add(toCQLString(columns.get(i), values[i]));
return joiner.toString();
}
private static String toCQLString(ColumnMetadata metadata, ByteBuffer key)
{
return String.format("%s = %s", metadata.name.toCQLString(), metadata.type.toCQLString(key));
}
public Token getToken()
{
return token;
}
public abstract ByteBuffer getKey();
public abstract int getKeyLength();
/**
* If this key occupies only part of a larger buffer, allocate a new buffer that is only as large as necessary.
* Otherwise, it returns this key.
*/
public DecoratedKey retainable()
{
return ByteBufferUtil.canMinimize(getKey())
? new BufferDecoratedKey(getToken(), HeapCloner.instance.clone(getKey()))
: this;
}
public void filterHash(long[] dest)
{
ByteBuffer key = getKey();
MurmurHash.hash3_x64_128(key, key.position(), key.remaining(), 0, dest);
}
/**
* A template factory method for creating decorated keys from their byte-comparable representation.
*/
static T fromByteComparable(ByteComparable byteComparable,
Version version,
IPartitioner partitioner,
BiFunction decoratedKeyFactory)
{
ByteSource.Peekable peekable = ByteSource.peekable(byteComparable.asComparableBytes(version));
// Decode the token from the first component of the multi-component sequence representing the whole decorated key.
Token token = partitioner.getTokenFactory().fromComparableBytes(ByteSourceInverse.nextComponentSource(peekable), version);
// Decode the key bytes from the second component.
byte[] keyBytes = ByteSourceInverse.getUnescapedBytes(ByteSourceInverse.nextComponentSource(peekable));
// Consume the terminator byte.
int terminator = peekable.next();
assert terminator == ByteSource.TERMINATOR : "Decorated key encoding must end in terminator.";
// Instantiate a decorated key from the decoded token and key bytes, using the provided factory method.
return decoratedKeyFactory.apply(token, keyBytes);
}
public static byte[] keyFromByteSource(ByteSource.Peekable peekableByteSource,
Version version,
IPartitioner partitioner)
{
assert version != Version.LEGACY; // reverse translation is not supported for LEGACY version.
// Decode the token from the first component of the multi-component sequence representing the whole decorated key.
// We won't use it, but the decoding also positions the byte source after it.
partitioner.getTokenFactory().fromComparableBytes(ByteSourceInverse.nextComponentSource(peekableByteSource), version);
// Decode the key bytes from the second component.
byte[] keyBytes = ByteSourceInverse.getUnescapedBytes(ByteSourceInverse.nextComponentSource(peekableByteSource));
int terminator = peekableByteSource.next();
assert terminator == ByteSource.TERMINATOR : "Decorated key encoding must end in terminator.";
return keyBytes;
}
}