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  1. Prepare
  2. Databases
  3. NoSQL - XML, MapReduce
  4. Map Reduce Advanced - Relational Join
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Map Reduce Advanced - Relational Join

  • qayum_khan_usa
     + 0 comments
    def mapper(record):
    # use SSN=Employee_ID as the joining key
    t,k,v = record.strip().split(',')
    if t[0]=='E' : k,v = v,k
    mapReducer.emitIntermediate( k, (t[0],v) )

def reducer(key, values):
    # a person can have multiple nicknames
    for p in [ v for t,v in values if t=='E' ] :
        for d in [ v for t,v in values if t=='D' ] :
            mapReducer.emit( (key,p,d) )