    001/*
    002 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved.
    003 *
    004 * Project and contact information: http://www.cascading.org/
    005 *
    006 * This file is part of the Cascading project.
    007 *
    008 * Licensed under the Apache License, Version 2.0 (the "License");
    009 * you may not use this file except in compliance with the License.
    010 * You may obtain a copy of the License at
    011 *
    012 *     http://www.apache.org/licenses/LICENSE-2.0
    013 *
    014 * Unless required by applicable law or agreed to in writing, software
    015 * distributed under the License is distributed on an "AS IS" BASIS,
    016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    017 * See the License for the specific language governing permissions and
    018 * limitations under the License.
    019 */
    020
    021package cascading.pipe.joiner;
    022
    023import java.util.Arrays;
    024import java.util.Iterator;
    025
    026import cascading.flow.FlowProcess;
    027import cascading.tuple.Fields;
    028import cascading.tuple.Tuple;
    029
    030/**
    031 * Class JoinerClosure wraps all incoming tuple streams with iterator instances allowing for just join implementations.
    032 * <p/>
    033 * This class is provided to a {@link Joiner#getIterator(JoinerClosure)} implementation, or to a {@link cascading.operation.Buffer}
    034 * via the {@link cascading.operation.BufferCall#getJoinerClosure()} method.
    035 * <p/>
    036 * All iterators returned by {@link #getIterator(int)} may be retrieved more than once to restart them except for the left
    037 * most iterator at position {@code 0} (zero).
    038 * <p/>
    039 * This iterator may only be iterated across once. All other iterators are backed by memory and possibly disk.
    040 */
    041public abstract class JoinerClosure
    042  {
    043  protected final FlowProcess flowProcess;
    044
    045  protected final Fields[] joinFields;
    046  protected final Fields[] valueFields;
    047
    048  public JoinerClosure( FlowProcess flowProcess, Fields[] joinFields, Fields[] valueFields )
    049    {
    050    this.flowProcess = flowProcess;
    051    this.joinFields = Arrays.copyOf( joinFields, joinFields.length );
    052    this.valueFields = Arrays.copyOf( valueFields, valueFields.length );
    053    }
    054
    055  public FlowProcess getFlowProcess()
    056    {
    057    return flowProcess;
    058    }
    059
    060  /**
    061   * Returns an array of {@link Fields} denoting the join fields or keys uses for each incoming pipe.
    062   * <p/>
    063   * The most left handed pipe will be in array position 0.
    064   *
    065   * @return an array of Fields
    066   */
    067  public Fields[] getJoinFields()
    068    {
    069    return joinFields;
    070    }
    071
    072  /**
    073   * Returns an array of all the incoming fields for each incoming pipe.
    074   * <p/>
    075   * The most left handed pipe will be in array position 0;
    076   *
    077   * @return an array of Fields
    078   */
    079  public Fields[] getValueFields()
    080    {
    081    return valueFields;
    082    }
    083
    084  public boolean isSelfJoin()
    085    {
    086    return valueFields.length == 1 && size() != valueFields.length;
    087    }
    088
    089  public abstract int size();
    090
    091  /**
    092   * Returns a Tuple Iterator for the given pipe position. Position 0 is the most left handed pipe passed to the prior
    093   * {@link cascading.pipe.CoGroup}.
    094   * <p/>
    095   * To restart an Iterator over a given pipe, this method must be called again.
    096   *
    097   * @param pos of type int
    098   * @return an Iterator of Tuple instances.
    099   */
    100  public abstract Iterator<Tuple> getIterator( int pos );
    101
    102  public abstract boolean isEmpty( int pos );
    103
    104  public abstract Tuple getGroupTuple( Tuple keysTuple );
    105  }