Hortonworks Certified Apache Hadoop 2.0 Developer (Pig and Hive Developer): HADOOP-PR000007

You are developing a MapReduce job for sales reporting. The mapper will process input keys representing the year (IntWritable) and input values representing product indentifies (Text).

Indentify what determines the data types used by the Mapper for a given job.

A. The key and value types specified in the JobConf.setMapInputKeyClass and JobConf.setMapInputValuesClass methods

B. The data types specified in HADOOP_MAP_DATATYPES environment variable

C. The mapper-specification.xml file submitted with the job determine the mapper's input key and value types.

D. The InputFormat used by the job determines the mapper's input key and value types.

Determine which best describes when the reduce method is first called in a MapReduce job?

A. Reducers start copying intermediate key-value pairs from each Mapper as soon as it has completed. The programmer can configure in the job what percentage of the intermediate data should arrive before the reduce method begins.

B. Reducers start copying intermediate key-value pairs from each Mapper as soon as it has completed. The reduce method is called only after all intermediate data has been copied and sorted.

C. Reduce methods and map methods all start at the beginning of a job, in order to provide optimal performance for map-only or reduce-only jobs.

D. Reducers start copying intermediate key-value pairs from each Mapper as soon as it has completed. The reduce method is called as soon as the intermediate key-value pairs start to arrive.

Consider the following two relations, A and B.

Which Pig statement combines A by its first field and B by its second field?

A. C = DOIN B BY a1, A by b2;

B. C = JOIN A by al, B by b2;

C. C = JOIN A a1, B b2;

D. C = JOIN A SO, B $1;