/*
* Copyright 1999-2015 dangdang.com.
* <p>
* Licensed 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.
* </p>
*/
package com.dangdang.ddframe.rdb.sharding.merger.pipeline.coupling.aggregation;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import java.math.BigDecimal;
import java.util.List;
/**
* 平均值聚合单元.
*
* @author gaohongtao
*/
@RequiredArgsConstructor
@Slf4j
public final class AverageAggregationUnit implements AggregationUnit {
private BigDecimal count;
private BigDecimal sum;
@Override
public void merge(final List<Comparable<?>> values) {
if (null == values || null == values.get(0) || null == values.get(1)) {
return;
}
if (null == count) {
count = new BigDecimal("0");
}
if (null == sum) {
sum = new BigDecimal("0");
}
count = count.add(new BigDecimal(values.get(0).toString()));
sum = sum.add(new BigDecimal(values.get(1).toString()));
log.trace("AVG result COUNT: {} SUM: {}", count, sum);
}
@Override
public Comparable<?> getResult() {
if (null == count || BigDecimal.ZERO.equals(count)) {
return count;
}
// TODO 通过metadata获取数据库的浮点数精度值
return sum.divide(count, 4, BigDecimal.ROUND_HALF_UP);
}
}