/*
* Copyright 2011 The Apache Software Foundation
*
* 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.lealone.hbase.command.merge;
import java.util.List;
import org.lealone.command.dml.Select;
import org.lealone.dbobject.index.IndexType;
import org.lealone.dbobject.table.IndexColumn;
import org.lealone.dbobject.table.Table;
import org.lealone.hbase.result.HBaseSerializedResult;
import org.lealone.result.DelegatedResult;
import org.lealone.result.ResultInterface;
public class HBaseMergedResult extends DelegatedResult {
public HBaseMergedResult(List<ResultInterface> results, Select newSelect, Select oldSelect) {
//1. 结果集串行化，为合并做准备
HBaseSerializedResult serializedResult = new HBaseSerializedResult(results, oldSelect);
Table table = newSelect.getTopTableFilter().getTable();
newSelect.getTopTableFilter().setIndex(
new HBaseMergedIndex(serializedResult, table, -1, IndexColumn.wrap(table.getColumns()), IndexType
.createScan(false)));
//2. 把多个结果集合并
ResultInterface mergedResult = newSelect.queryGroupMerge();
//3. 计算合并后的结果集,
//例如oldSelect="select avg"时，在分布式环境要转成newSelect="select count, sum"，
//此时就由count, sum来算出avg
ResultInterface calculatedResult = oldSelect.calculate(mergedResult, newSelect);
//4. 如果不存在avg、stddev这类需要拆分为count、sum的计算，此时mergedResult和calculatedResult是同一个实例
//否则就是不同实例，需要再一次按oldSelect合并结果集
if (mergedResult != calculatedResult) {
table = oldSelect.getTopTableFilter().getTable();
oldSelect.getTopTableFilter().setIndex(
new HBaseMergedIndex(calculatedResult, table, -1, IndexColumn.wrap(table.getColumns()), IndexType
.createScan(false)));
//5. 最终结果集
result = oldSelect.queryGroupMerge();
//6. 立刻关闭中间结果集
serializedResult.close();
mergedResult.close();
calculatedResult.close();
} else {
result = mergedResult;
}
}
}