/**
* 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.tajo.engine.planner.physical;
import org.apache.tajo.worker.TaskAttemptContext;
import org.apache.tajo.catalog.Schema;
import org.apache.tajo.engine.planner.logical.LimitNode;
import org.apache.tajo.storage.Tuple;
import java.io.IOException;
public class LimitExec extends UnaryPhysicalExec {
private final long fetchFirstNum;
private long fetchCount;
public LimitExec(TaskAttemptContext context, Schema inSchema,
Schema outSchema, PhysicalExec child, LimitNode limit) {
super(context, inSchema, outSchema, child);
this.fetchFirstNum = limit.getFetchFirstNum();
this.fetchCount = 0;
}
@Override
public Tuple next() throws IOException {
Tuple tuple = child.next();
fetchCount++;
if (fetchCount > fetchFirstNum || tuple == null) {
return null;
}
return tuple;
}
public void rescan() throws IOException {
super.init();
fetchCount = 0;
}
}