    001    /*
    002     * Copyright (c) 2007-2014 Concurrent, 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
    021    package cascading.pipe.joiner;
    022
    023    import java.beans.ConstructorProperties;
    024    import java.util.Collections;
    025    import java.util.Iterator;
    026    import java.util.List;
    027
    028    import cascading.tuple.Fields;
    029    import cascading.tuple.Tuple;
    030
    031    /**
    032     * Class OuterJoin will return an {@link Iterator} that will iterate over a given {@link Joiner} and return tuples that represent
    033     * and outer join of the CoGrouper internal grouped tuple collections.
    034     * <p/>
    035     * Joins perform based on the equality of the join keys. In the case of null values, Java treats two
    036     * null values as equivalent. SQL does not treat null values as equal. To produce SQL like results in a given
    037     * join, a new {@link java.util.Comparator} will need to be used on the joined values to prevent null from
    038     * equaling null. As a convenience, see the {@link cascading.util.NullNotEquivalentComparator} class.
    039     */
    040    public class OuterJoin extends BaseJoiner
    041      {
    042      public OuterJoin()
    043        {
    044        }
    045
    046      @ConstructorProperties({"fieldDeclaration"})
    047      public OuterJoin( Fields fieldDeclaration )
    048        {
    049        super( fieldDeclaration );
    050        }
    051
    052      public Iterator<Tuple> getIterator( JoinerClosure closure )
    053        {
    054        return new JoinIterator( closure );
    055        }
    056
    057      public int numJoins()
    058        {
    059        return -1;
    060        }
    061
    062      public static class JoinIterator extends InnerJoin.JoinIterator
    063        {
    064        List[] singletons;
    065
    066        public JoinIterator( JoinerClosure closure )
    067          {
    068          super( closure );
    069          }
    070
    071        @Override
    072        protected void init()
    073          {
    074          singletons = new List[ closure.size() ];
    075
    076          for( int i = 0; i < singletons.length; i++ )
    077            {
    078            if( isOuter( i ) )
    079              singletons[ i ] = Collections.singletonList( Tuple.size( closure.getValueFields()[ i ].size() ) );
    080            }
    081
    082          super.init();
    083          }
    084
    085        protected boolean isOuter( int i )
    086          {
    087          return closure.isEmpty( i );
    088          }
    089
    090        @Override
    091        protected Iterator getIterator( int i )
    092          {
    093          if( singletons[ i ] == null ) // let init() decide
    094            return super.getIterator( i );
    095
    096          return singletons[ i ].iterator();
    097          }
    098        }
    099      }