/**
 * 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;
  }
}