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The Ultimate Cheat Sheet On Hadoop

Top 20 frequently asked questions to test your Hadoop knowledge given in the below Hadoop cheat sheet. Try finding your own answers and match the answers given here.




Question #1 

You have written a MapReduce job that will process 500 million input records and generate 500 million key-value pairs. The data is not uniformly distributed. Your MapReduce job will create a significant amount of intermediate data that it needs to transfer between mappers and reducers which is a potential bottleneck. A custom implementation of which of the following interfaces is most likely to reduce the amount of intermediate data transferred across the network?



A. Writable
B. WritableComparable
C. InputFormat
D. OutputFormat
E. Combiner
F. Partitioner
Ans: e




Question #2 

Where is Hive metastore stored by default ?


A. In HDFS
B. In client machine in the form of a flat file.
C. In client machine in a derby database
D. In lib directory of HADOOP_HOME, and requires HADOOP_CLASSPATH to be modified.
Ans: c




Question…

PL/SQL Sample code and error handling mechanism

SAMPLE PL/SQL


CREATE TABLE dummy
( dummy_value       VARCHAR2(1));
DECLARE
  -- Define local variable.
  my_string VARCHAR2(1) := ' ';
  my_number NUMBER;
BEGIN
  -- Select a white space into a local variable.
  SELECT ' ' INTO my_string FROM dummy;
  -- Attempt to assign a single white space to a number.
  my_number := TO_NUMBER(my_string);
EXCEPTION
 WHEN no_data_found THEN
   dbms_output.put_line('SELECT-INTO'||CHR(10)||SQLERRM);
END;
/

Output and Error:
The program returns the following output, which illustrates formatting user- defined exceptions. 

The CHR(10) inserts a line return and provides a clean break between the program's SQLCODE and SQLERRM messages:

RAISE my_error SQLCODE [1] 
SQLERRM [User-Defined Exception]

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