hadoop - Writing MApreduce code for counting number of records

Question

I want to write a mapreduce code for counting number of records in given CSV file.I am not getting what to do in map and what to do in reduce how should I go about solving this can anyone suggest something?

Answer 1

• Your map should emit 1 for each record read
• your combiner should emit the sum of all the "1"s it got (sub total per map)
• you reducer should emit the the grand total number of records