/**
* 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.clock;
import org.apache.cassandra.db.Column;
import org.apache.cassandra.db.IClock.ClockRelationship;
import org.apache.cassandra.utils.FBUtilities;
/**
* Keeps the column with the highest timestamp. If both are equal
* return the left column.
*/
public final class TimestampReconciler extends AbstractReconciler
{
public static final TimestampReconciler instance = new TimestampReconciler();
private TimestampReconciler()
{/* singleton */}
public Column reconcile(Column left, Column right)
{
ClockRelationship cr = left.clock().compare(right.clock());
switch (cr)
{
case EQUAL:
// tombstones take precedence. (if both are tombstones, then it doesn't matter which one we use.)
if (left.isMarkedForDelete())
return left;
if (right.isMarkedForDelete())
return right;
// break ties by comparing values.
return FBUtilities.compareByteArrays(left.value(), right.value()) < 0 ? right : left;
case GREATER_THAN:
return left;
case LESS_THAN:
return right;
default:
throw new IllegalArgumentException(
"Timestamp clocks must either be equal, greater then or less than: " + cr);
}
}
}