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courses:mapreduce-tutorial:step-4 [2012/01/24 21:10]
straka 		courses:mapreduce-tutorial:step-4 [2012/01/24 21:29]
straka
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 ====== MapReduce Tutorial : Counters ====== ====== MapReduce Tutorial : Counters ======
  
-Sometimes it is useful to +Sometimes it is useful to count events differently than outputting them (key, value) pairs. For that reason Hadoop offers simple counter framework. 
 + 
 +<code perl> 
 +sub map { 
 +  my ($self, $key, $value, $context) = @_; 
 +  
 +  $context->counter($group, $name, $increment); 
 +} 
 +</code> 
 + 
 +===== Exercise ===== 
 + 
 +Run a MR job on /home/straka/wiki/cs-text, which uses counters to count the number of articles according to their first letter (ignoring the case and possible diacritics). 
 + 
 +{{.:step-4-solution.txt|Solution.pl}}
  
-{{.:step-3:exercise.txt|Reseni.pl}} 
-{{filelist>:snippets:dokuwiki:plugin-*.tar.gz&style=table&tableheader=1&tableshowdate=1&tableshowsize=1}} 

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