5. Advanced Joins
by Jon Lentz, Brian Femiano, Jonathan R. Owens
Hadoop Real-World Solutions Cookbook
- Hadoop Real-World Solutions Cookbook
- Table of Contents
- Hadoop Real-World Solutions Cookbook
- Credits
- About the Authors
- About the Reviewers
- www.packtpub.com
- Preface
- 1. Hadoop Distributed File System – Importing and Exporting Data
- Introduction
- Importing and exporting data into HDFS using Hadoop shell commands
- Moving data efficiently between clusters using Distributed Copy
- Importing data from MySQL into HDFS using Sqoop
- Exporting data from HDFS into MySQL using Sqoop
- Configuring Sqoop for Microsoft SQL Server
- Exporting data from HDFS into MongoDB
- Importing data from MongoDB into HDFS
- Exporting data from HDFS into MongoDB using Pig
- Using HDFS in a Greenplum external table
- Using Flume to load data into HDFS
- 2. HDFS
- Introduction
- Reading and writing data to HDFS
- Compressing data using LZO
- Reading and writing data to SequenceFiles
- Using Apache Avro to serialize data
- Using Apache Thrift to serialize data
- Using Protocol Buffers to serialize data
- Setting the replication factor for HDFS
- Setting the block size for HDFS
- 3. Extracting and Transforming Data
- Introduction
- Transforming Apache logs into TSV format using MapReduce
- Using Apache Pig to filter bot traffic from web server logs
- Using Apache Pig to sort web server log data by timestamp
- Using Apache Pig to sessionize web server log data
- Using Python to extend Apache Pig functionality
- Using MapReduce and secondary sort to calculate page views
- Using Hive and Python to clean and transform geographical event data
- Using Python and Hadoop Streaming to perform a time series analytic
- Using MultipleOutputs in MapReduce to name output files
- Creating custom Hadoop Writable and InputFormat to read geographical event data
- 4. Performing Common Tasks Using Hive, Pig, and MapReduce
- Introduction
- Using Hive to map an external table over weblog data in HDFS
- Using Hive to dynamically create tables from the results of a weblog query
- Using the Hive string UDFs to concatenate fields in weblog data
- Using Hive to intersect weblog IPs and determine the country
- Generating n-grams over news archives using MapReduce
- Using the distributed cache in MapReduce to find lines that contain matching keywords over news archives
- Using Pig to load a table and perform a SELECT operation with GROUP BY
- 5. Advanced Joins
- Introduction
- Joining data in the Mapper using MapReduce
- Joining data using Apache Pig replicated join
- Joining sorted data using Apache Pig merge join
- Joining skewed data using Apache Pig skewed join
- Using a map-side join in Apache Hive to analyze geographical events
- Using optimized full outer joins in Apache Hive to analyze geographical events
- Joining data using an external key-value store (Redis)
- 6. Big Data Analysis
- Introduction
- Counting distinct IPs in weblog data using MapReduce and Combiners
- Using Hive date UDFs to transform and sort event dates from geographic event data
- Using Hive to build a per-month report of fatalities over geographic event data
- Implementing a custom UDF in Hive to help validate source reliability over geographic event data
- Marking the longest period of non-violence using Hive MAP/REDUCE operators and Python
- Calculating the cosine similarity of artists in the Audioscrobbler dataset using Pig
- Trim Outliers from the Audioscrobbler dataset using Pig and datafu
- 7. Advanced Big Data Analysis
- 8. Debugging
- Introduction
- Using Counters in a MapReduce job to track bad records
- Developing and testing MapReduce jobs with MRUnit
- Developing and testing MapReduce jobs running in local mode
- Enabling MapReduce jobs to skip bad records
- Using Counters in a streaming job
- Updating task status messages to display debugging information
- Using illustrate to debug Pig jobs
- 9. System Administration
- 10. Persistence Using Apache Accumulo
- Introduction
- Designing a row key to store geographic events in Accumulo
- Using MapReduce to bulk import geographic event data into Accumulo
- Setting a custom field constraint forinputting geographic event data in Accumulo
- Limiting query results using the regex filtering iterator
- Counting fatalities for different versions of the same key using SumCombiner
- Enforcing cell-level security on scans using Accumulo
- Aggregating sources in Accumulo using MapReduce
- Index
In this chapter, we will cover:
- Joining data in the Mapper using MapReduce
- Joining data using Apache Pig replicated join
- Joining sorted data using Apache Pig merge join
- Joining skewed data using Apache Pig skewed join
- Using a map-side join in Apache Hive to analyze geographical events
- Using optimized full outer joins in Apache Hive to analyze geographical events
- Joining data using an external key-value store (Redis)
In most processing environments, there will be a need to join multiple datasets to produce some final result. Unfortunately, joins in MapReduce are non-trivial and can be an expensive operation. This chapter will demonstrate different approaches to joining data in Hadoop using a number of tools, including Java MapReduce, Apache Pig, and Apache Hive. In addition, this chapter will demonstrate how to leverage external memory resources using Hadoop MapReduce.
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