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POCan I assign sequece number to the records in reducer
 

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  1. POCan I assign sequece number to the records in reducer
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    <p>I wish to assign a sequence number to the events coming from the Mapper class based on the time the events happened.</p> <p>For example, I have 100 events which have a time in them. I wish to sort them based on the time and then in the reducer phase assign a sequence number to them. Also, remove the duplicate records in the reducer phase if they are duplicate (Same events happening at the same time).</p> <p>Mapper method:</p> <pre><code>public class EventMapper extends Mapper&lt;LongWritable, Text, Text, Event&gt; { public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { String line = value.toString(); Text newKey; Event e = new Event(); e.setAllValues(line); newKey = new Text(e.getKey()); context.write(newKey, e); } } </code></pre> <p>Reducer Method (Something what I wish for):</p> <pre><code>public class EventReducer extends Reducer&lt;Text, Event, Text, Text&gt; { public void reduce(Text key, Iterator&lt;Event&gt; itrtr, Context context) throws IOException, InterruptedException { Event e; List&lt;Event&gt; l = new ArrayList&lt;Event&gt;(); while(itrtr.hasNext()){ e = itrtr.next(); l.add(e); } Collections.sort(l); long i = 1; for (Event event : l) { event.setId(++i); context.write(key, new Text(event.toString())); } } } </code></pre> <p>I get all the ids as 0. How can I achieve this? Am I following a wrong approach.</p> <p>Here is the Event class:</p> <pre><code>public class Event implements Writable, WritableComparable&lt;Event&gt; { //Some variables and getter + setters @Override public String toString() { String delimiter1 = "|"; return this.date + delimiter1 + this.evName + delimiter1 + this.evType + delimiter1 + this.evValue + delimiter1 + this.name + delimiter1 + this.id; } @Override public void readFields(DataInput in) throws IOException { try { this.date = converStringToDate((WritableUtils.readString(in)).toString(), dateFormat); } catch (ParseException ex) { System.out.println("Wront date . Pe"); } this.evName = WritableUtils.readString(in); this.evType = WritableUtils.readString(in); this.evValue = WritableUtils.readString(in); this.name = WritableUtils.readString(in); this.id = WritableUtils.readVLong(in); } @Override public void write(DataOutput out) throws IOException { // TODO Auto-generated method stub WritableUtils.writeString(out, this.convertDateToString(date)); WritableUtils.writeString(out, evName); WritableUtils.writeString(out, evType); WritableUtils.writeString(out, evValue); WritableUtils.writeString(out, name); WritableUtils.writeVLong(out, id); } public int compareTo(Event o) { long value = this.getDate().getTime() - o.getDate().getTime(); if (value == 0) { return 0; } else if (value &gt; 1) { return -1; } else { return 1; } } public void setAllValues(String input) { String[] arrValues = input.split(delimiter); System.out.println("No of Values = " + arrValues.length); try { this.date = converStringToDate(arrValues[0], dateFormat); } catch (ParseException pe) { System.out.println("pe&gt; Error in date"); } if (arrValues.length &gt;= 2) { this.evName = arrValues[1]; } if (arrValues.length &gt;= 3) { this.evType = arrValues[2]; } if (arrValues.length &gt;= 4) { this.evValue = arrValues[3]; } if (arrValues.length &gt;= 5) { this.name = arrValues[4]; } } public String getKey() { //return convertDateToString(this.date) + this.evName + this.evType; return this.evName; } } </code></pre>
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    1. USexplorer
    1. USexplorer
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    1. COCan you post the code for class Event, or if it's not your class can you post the fully qualified name? Is Event a hadoop Writable?
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      1. POCan I assign sequece number to the records in reducer
      1. USChris Gerken
    2. CO@Chris Added the Event class code here
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      1. POCan I assign sequece number to the records in reducer
      1. USexplorer
    3. COThanks. And where is the setAllValues(String) method source?
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      1. POCan I assign sequece number to the records in reducer
      1. USChris Gerken
 

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