/*
* 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.resultset.memory;
import com.dangdang.ddframe.rdb.sharding.merger.resultset.memory.row.OrderByResultSetRow;
import com.dangdang.ddframe.rdb.sharding.merger.resultset.memory.row.ResultSetRow;
import com.dangdang.ddframe.rdb.sharding.parser.result.merger.OrderByColumn;
import com.google.common.base.Optional;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
/**
* 基于内存排序的结果集抽象类.
*
* @author gaohongtao
* @author zhangliang
*/
public abstract class AbstractMemoryOrderByResultSet extends AbstractMemoryResultSet {
private final List<OrderByColumn> orderByColumns;
private Iterator<OrderByResultSetRow> orderByResultSetRowIterator;
public AbstractMemoryOrderByResultSet(final List<ResultSet> resultSets, final List<OrderByColumn> orderByColumns) throws SQLException {
super(resultSets);
this.orderByColumns = orderByColumns;
}
@Override
protected void initRows(final List<ResultSet> resultSets) throws SQLException {
List<OrderByResultSetRow> orderByResultSetRows = new LinkedList<>();
for (ResultSet each : resultSets) {
while (each.next()) {
orderByResultSetRows.add(new OrderByResultSetRow(each, orderByColumns));
}
}
Collections.sort(orderByResultSetRows);
orderByResultSetRowIterator = orderByResultSetRows.iterator();
}
@Override
protected Optional<? extends ResultSetRow> nextRow() throws SQLException {
if (orderByResultSetRowIterator.hasNext()) {
return Optional.of(orderByResultSetRowIterator.next());
}
return Optional.absent();
}
}