Book Image

Hadoop Beginner's Guide

Book Image

Hadoop Beginner's Guide

Overview of this book

Data is arriving faster than you can process it and the overall volumes keep growing at a rate that keeps you awake at night. Hadoop can help you tame the data beast. Effective use of Hadoop however requires a mixture of programming, design, and system administration skills."Hadoop Beginner's Guide" removes the mystery from Hadoop, presenting Hadoop and related technologies with a focus on building working systems and getting the job done, using cloud services to do so when it makes sense. From basic concepts and initial setup through developing applications and keeping the system running as the data grows, the book gives the understanding needed to effectively use Hadoop to solve real world problems.Starting with the basics of installing and configuring Hadoop, the book explains how to develop applications, maintain the system, and how to use additional products to integrate with other systems.While learning different ways to develop applications to run on Hadoop the book also covers tools such as Hive, Sqoop, and Flume that show how Hadoop can be integrated with relational databases and log collection.In addition to examples on Hadoop clusters on Ubuntu uses of cloud services such as Amazon, EC2 and Elastic MapReduce are covered.
Table of Contents (19 chapters)
Hadoop Beginner's Guide
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Time for action – redefining the table with the correct column separator


Let's fix our table specification as follows:

  1. Create the following file as commands.hql:

    DROP TABLE ufodata ;
    CREATE TABLE ufodata(sighted string, reported string, sighting_location string,
    shape string, duration string, description string)
    ROW FORMAT DELIMITED
    FIELDS TERMINATED BY '\t' ;
    LOAD DATA INPATH '/tmp/ufo.tsv' OVERWRITE INTO TABLE ufodata ;
  2. Copy the data file onto HDFS:

    $ hadoop fs -put ufo.tsv /tmp/ufo.tsv
    
  3. Execute the HiveQL script:

    $ hive -f commands.hql 
    

    You will receive the following response:

    OK
    Time taken: 5.821 seconds
    OK
    Time taken: 0.248 seconds
    Loading data to table default.ufodata
    Deleted hdfs://head:9000/user/hive/warehouse/ufodata
    OK
    Time taken: 0.285 seconds
    
  4. Validate the number of rows in the table:

    $ hive -e "select count(*) from ufodata;"
    

    You will receive the following response:

    OK
    61393
    Time taken: 28.077 seconds
    
  5. Validate the contents of the reported column:

    $ hive -e "select reported from ufodata...