/*
* 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.reducer;
import com.dangdang.ddframe.rdb.sharding.merger.ResultSetMergeContext;
import com.dangdang.ddframe.rdb.sharding.merger.resultset.delegate.AbstractDelegateResultSet;
import java.sql.ResultSet;
import java.sql.SQLException;
/**
* 迭代归并的聚集结果集.
*
* @author gaohongtao
* @author zhangliang
*/
public final class IteratorReducerResultSet extends AbstractDelegateResultSet {
private int resultSetIndex = 1;
public IteratorReducerResultSet(final ResultSetMergeContext resultSetMergeContext) throws SQLException {
super(resultSetMergeContext.getShardingResultSets().getResultSets());
}
@Override
protected boolean firstNext() throws SQLException {
return processCurrent();
}
@Override
protected boolean afterFirstNext() throws SQLException {
return processCurrent() || (!isOutOfIndex() && processNext());
}
private boolean processCurrent() throws SQLException {
return getDelegate().next();
}
private boolean isOutOfIndex() {
return resultSetIndex >= getResultSets().size();
}
private boolean processNext() throws SQLException {
ResultSet resultSet = getResultSets().get(resultSetIndex++);
setDelegate(resultSet);
return resultSet.next();
}
}