/*
* 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.openjpa.slice.policy;
import java.util.List;
import org.apache.openjpa.slice.DistributionPolicy;
import org.apache.openjpa.slice.PObject;
/**
* Distributes the instances uniformly among the available slices
* based on the integral value of the persistence identifier.
* <br>
* Given {@code M} slices and {@code N} instances whose identity
* value is uniformly distributed, this policy will persist these
* instances such that
* <LI>each slice will have N/M instances
* <LI>the identity of the instances in the {@code i}-th slice
* will be divisible by {@code i}.
*
* @author Pinaki Poddar
*
*/
public class UniformDistributionPolicy implements DistributionPolicy {
@Override
public String distribute(Object pc, List<String> slices, Object context) {
int N = slices.size();
for (int i = N; i > 0; i--) {
PObject p = (PObject)pc;
if (p.getId()%i == 0) return slices.get(i-1);
}
return slices.get(0);
}
}