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https://issues.apache.org/jira/browse/HADOOP-2234?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12544127
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Edward Yoon commented on HADOOP-2234:
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Michael:
I tryed either TableMap and MapReduceBase + Mapper. please ignore it.
> [hbase] TableInputFormat erroneously aggregates map values
> ----------------------------------------------------------
>
> Key: HADOOP-2234
> URL: https://issues.apache.org/jira/browse/HADOOP-2234
> Project: Hadoop
> Issue Type: Bug
> Components: contrib/hbase
> Reporter: stack
> Priority: Minor
>
> Edward Yoon reports the following phenomeon:
> Given a table:
> {code}
> [21:38] <edward__> row1 a: <aa> b: <bb> a:ca <aa2>
> [21:38] <edward__> row2 a: <aa3> b: <bb3>
> [21:38] <edward__> row3 a: <aa4> b: <bb4>
> {code}
> This map code:
> {code}
> public void map(WritableComparable key, Writable value,
> OutputCollector output, Reporter reporter) throws IOException {
> if (m_collector.collector == null) {
> m_collector.collector = output;
> }
> HStoreKey hKey = (HStoreKey) key;
> MapWritable newValue = (MapWritable) value;
> newValue.put(new Text("row:" + hKey.getRow().toString()), new
> ImmutableBytesWritable(hKey.getRow().toString().getBytes()));
>
> Map<Text, String> log = new HashMap<Text, String>();
> for(Map.Entry<Writable, Writable> e : newValue.entrySet()) {
> log.put(e.getKey(), e.getValue()); //abbreviation code.
> }
>
> LOG.info(log);
> output.collect(hKey, newValue);
> }
> {code}
> ... produces the following.
> {code}
> 07/11/20 14:07:53 INFO jvm.JvmMetrics: Initializing JVM Metrics with
> processName=JobTracker, sessionId=
> 07/11/20 14:07:53 WARN mapred.JobClient: No job jar file set. User classes
> may not be found. See JobConf(Class) or JobConf#setJar(String).
> 07/11/20 14:07:53 INFO mapred.MapTask: numReduceTasks: 1
> 07/11/20 14:07:53 INFO algebra.SortMap: {a:=aa, b:=bb, a:da=aa44, a:ca=aa2}
> 07/11/20 14:07:53 INFO algebra.SortMap: {a:=aa3, b:=bb3, a:da=aa44, a:ca=aa2}
> 07/11/20 14:07:53 INFO algebra.SortMap: {a:=aa4, b:=bb4, a:da=aa44, a:ca=aa2}
> 07/11/20 14:07:53 INFO mapred.LocalJobRunner:
> 07/11/20 14:07:53 INFO mapred.TaskRunner: Task 'map_0000' done.
> 07/11/20 14:07:53 INFO algebra.SortReduce: {a:=aa, b:=bb, a:da=aa44, a:ca=aa2}
> 07/11/20 14:07:53 INFO algebra.SortReduce: {a:=aa3, b:=bb3, a:da=aa44,
> a:ca=aa2}
> 07/11/20 14:07:53 INFO algebra.SortReduce: {a:=aa4, b:=bb4, a:da=aa44,
> a:ca=aa2}
> 07/11/20 14:07:53 INFO mapred.LocalJobRunner: reduce > reduce
> 07/11/20 14:07:53 INFO mapred.TaskRunner: Task 'reduce_9ji2mr' done.
> {code}
> Notice how content from the first row is present when you output the second
> and third rows.
> The problem is that in TIF, after calling scanner.next, it copies the
> scanner.next value to the passed in MapWritable value (converting from
> TreeMap to MapWritable). It resets the TreeMap passed to the scanner.next
> each time but not the passed in MapWritable.
> There is a similar problem in the reduce where the outputter is collecting
> together values (see log above). Need to figure whats going on here. Below
> is the reduce code:
> {code}
> [22:03] <edward__> while (values.hasNext()) {
> [22:03] <edward__> MapWritable data = (MapWritable) values.next();
> [22:03] <edward__> Map<String, String> log = new HashMap<String,
> String>();
> [22:03] <edward__> for (Map.Entry<Writable, Writable> e :
> data.entrySet()) {
> [22:03] <edward__> log.put(e.getKey().toString(), new
> String(((ImmutableBytesWritable) e
> [22:03] <edward__> .getValue()).get()));
> [22:03] <edward__> }
> [22:03] <edward__> LOG.info(log);
> {code}
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