001    /*
002     * Copyright (c) 2007-2015 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      }