/*
* 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.solr.search.facet;
import java.io.IOException;
import java.util.List;
import org.apache.lucene.queries.function.ValueSource;
public class VarianceAgg extends SimpleAggValueSource {
public VarianceAgg(ValueSource vs) {
super("variance", vs);
}
@Override
public SlotAcc createSlotAcc(FacetContext fcontext, int numDocs, int numSlots) throws IOException {
return new VarianceSlotAcc(getArg(), fcontext, numSlots);
}
@Override
public FacetMerger createFacetMerger(Object prototype) {
return new Merger();
}
private static class Merger extends FacetDoubleMerger {
long count;
double sumSq;
double sum;
@Override
@SuppressWarnings("unchecked")
public void merge(Object facetResult, Context mcontext1) {
List<Number> numberList = (List<Number>)facetResult;
this.count += numberList.get(0).longValue();
this.sumSq += numberList.get(1).doubleValue();
this.sum += numberList.get(2).doubleValue();
}
@Override
public Object getMergedResult() {
return this.getDouble();
}
@Override
protected double getDouble() {
double val = count == 0 ? 0.0d : (sumSq/count)-Math.pow(sum/count, 2);
return val;
}
};
}