001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    
019    package org.apache.hadoop.mapred.join;
020    
021    import java.io.IOException;
022    import java.util.PriorityQueue;
023    
024    import org.apache.hadoop.classification.InterfaceAudience;
025    import org.apache.hadoop.classification.InterfaceStability;
026    import org.apache.hadoop.io.Writable;
027    import org.apache.hadoop.io.WritableComparable;
028    import org.apache.hadoop.io.WritableComparator;
029    import org.apache.hadoop.io.WritableUtils;
030    import org.apache.hadoop.util.ReflectionUtils;
031    import org.apache.hadoop.mapred.JobConf;
032    import org.apache.hadoop.mapred.RecordReader;
033    
034    /**
035     * Base class for Composite join returning values derived from multiple
036     * sources, but generally not tuples.
037     * @deprecated Use 
038     * {@link org.apache.hadoop.mapreduce.lib.join.MultiFilterRecordReader} instead
039     */
040    @Deprecated
041    @InterfaceAudience.Public
042    @InterfaceStability.Stable
043    public abstract class MultiFilterRecordReader<K extends WritableComparable,
044                                                  V extends Writable>
045        extends CompositeRecordReader<K,V,V>
046        implements ComposableRecordReader<K,V> {
047    
048      private Class<? extends Writable> valueclass;
049      private TupleWritable ivalue;
050    
051      public MultiFilterRecordReader(int id, JobConf conf, int capacity,
052          Class<? extends WritableComparator> cmpcl) throws IOException {
053        super(id, capacity, cmpcl);
054        setConf(conf);
055      }
056    
057      /**
058       * For each tuple emitted, return a value (typically one of the values
059       * in the tuple).
060       * Modifying the Writables in the tuple is permitted and unlikely to affect
061       * join behavior in most cases, but it is not recommended. It's safer to
062       * clone first.
063       */
064      protected abstract V emit(TupleWritable dst) throws IOException;
065    
066      /**
067       * Default implementation offers {@link #emit} every Tuple from the
068       * collector (the outer join of child RRs).
069       */
070      protected boolean combine(Object[] srcs, TupleWritable dst) {
071        return true;
072      }
073    
074      /** {@inheritDoc} */
075      public boolean next(K key, V value) throws IOException {
076        if (jc.flush(ivalue)) {
077          WritableUtils.cloneInto(key, jc.key());
078          WritableUtils.cloneInto(value, emit(ivalue));
079          return true;
080        }
081        jc.clear();
082        K iterkey = createKey();
083        final PriorityQueue<ComposableRecordReader<K,?>> q = getRecordReaderQueue();
084        while (!q.isEmpty()) {
085          fillJoinCollector(iterkey);
086          jc.reset(iterkey);
087          if (jc.flush(ivalue)) {
088            WritableUtils.cloneInto(key, jc.key());
089            WritableUtils.cloneInto(value, emit(ivalue));
090            return true;
091          }
092          jc.clear();
093        }
094        return false;
095      }
096    
097      /** {@inheritDoc} */
098      @SuppressWarnings("unchecked") // Explicit check for value class agreement
099      public V createValue() {
100        if (null == valueclass) {
101          final Class<?> cls = kids[0].createValue().getClass();
102          for (RecordReader<K,? extends V> rr : kids) {
103            if (!cls.equals(rr.createValue().getClass())) {
104              throw new ClassCastException("Child value classes fail to agree");
105            }
106          }
107          valueclass = cls.asSubclass(Writable.class);
108          ivalue = createInternalValue();
109        }
110        return (V) ReflectionUtils.newInstance(valueclass, null);
111      }
112    
113      /**
114       * Return an iterator returning a single value from the tuple.
115       * @see MultiFilterDelegationIterator
116       */
117      protected ResetableIterator<V> getDelegate() {
118        return new MultiFilterDelegationIterator();
119      }
120    
121      /**
122       * Proxy the JoinCollector, but include callback to emit.
123       */
124      protected class MultiFilterDelegationIterator
125          implements ResetableIterator<V> {
126    
127        public boolean hasNext() {
128          return jc.hasNext();
129        }
130    
131        public boolean next(V val) throws IOException {
132          boolean ret;
133          if (ret = jc.flush(ivalue)) {
134            WritableUtils.cloneInto(val, emit(ivalue));
135          }
136          return ret;
137        }
138    
139        public boolean replay(V val) throws IOException {
140          WritableUtils.cloneInto(val, emit(ivalue));
141          return true;
142        }
143    
144        public void reset() {
145          jc.reset(jc.key());
146        }
147    
148        public void add(V item) throws IOException {
149          throw new UnsupportedOperationException();
150        }
151    
152        public void close() throws IOException {
153          jc.close();
154        }
155    
156        public void clear() {
157          jc.clear();
158        }
159      }
160    
161    }