Hi Yong,
A few ways to understand a problem (with Hadoop) :
1) Write tests, using MRUnit for example (http://mrunit.apache.org/)
2) Use @Override to make sure you are indeed overriding a method
3) Use a break point while debugging
The answer to your current problem : o.a.h.mapreduce.Reducer method has no
Iterator parameter but it does have a Iterable parameter...
Regards
Bertrand
PS : It is absolutely not related to HBase.
On Thu, Nov 15, 2012 at 8:42 PM, yonghu <yongyong...@gmail.com> wrote:
> Dear all,
>
> I use HBase as data source and hdfs as data sink. I wrote the program
> which calculate the versions for each cell as follows:
>
> public class ReturnMore { //only Map side has no problem, has already
> returned 3 versions
>
> public static class Map extends TableMapper<Text, Text>{
> private Text outkey = new Text();
> private Text outval = new Text();
> public void map(ImmutableBytesWritable key, Result values, Context
> context){
> KeyValue[] kvs = values.raw();
> String row_key;
> String col_fam;
> String col;
> String val;
> String finalKey;
> String finalValue;
> for(KeyValue kv : kvs){
> row_key = Bytes.toString(kv.getRow());
> col_fam = Bytes.toString(kv.getFamily());
> col = Bytes.toString(kv.getQualifier());
> val = Bytes.toString(kv.getValue());
> finalKey = row_key + "/" + col_fam + "/" + col;
> finalValue = new Long(kv.getTimestamp()).toString() + "/" +
> val;
> outkey.set(finalKey);
> outval.set(finalValue);
> try {
> context.write(outkey, outval);
> } catch (IOException e) {
> e.printStackTrace();
> } catch (InterruptedException e) {
> e.printStackTrace();
> }
> }
> }
> }
>
> public static class Reduce extends Reducer<Text, Text, Text,
> IntWritable>{ //the desired output is key + 3
> private IntWritable occ = new IntWritable();
> public void reduce(Text key, Iterator<Text> values, Context
> context){
> int i = 0;
> while(values.hasNext()){
> i++;
> }
> occ.set(i);
> try {
> context.write(key, occ);
> } catch (IOException e) {
> e.printStackTrace();
> } catch (InterruptedException e) {
> e.printStackTrace();
> }
> }
> }
> public static void main(String[] args) throws Exception{
> Configuration conf = HBaseConfiguration.create();
> Job job = new Job(conf);
> job.setJarByClass(ReturnMore.class);
> Scan scan = new Scan();
> scan.setMaxVersions();
> job.setReducerClass(Reduce.class);
> job.setOutputKeyClass(Text.class);
> job.setOutputValueClass(IntWritable.class);
> job.setNumReduceTasks(1);
> TableMapReduceUtil.initTableMapperJob("test", scan, Map.class,
> Text.class, Text.class, job);
> FileSystem file = FileSystem.get(conf);
> Path path = new Path("/hans/test/");
> if(file.exists(path)){
> file.delete(path,true);
> }
> FileOutputFormat.setOutputPath(job, path);
> System.exit(job.waitForCompletion(true)?0:1);
> }
> }
>
> I tested this code in both hbase 0.92.1 and 0.94. However, if I run
> this code, it always outputs the content for each cell not as the
> output as I defined in reduce function (key + occurrence for each
> cell). Can anyone give me advices? By the way, I run it on
> pseudo-mode.
>
> regards!
>
> Yong
>
--
Bertrand Dechoux
