Book Image

Learning Spark SQL

By : Aurobindo Sarkar
Book Image

Learning Spark SQL

By: Aurobindo Sarkar

Overview of this book

In the past year, Apache Spark has been increasingly adopted for the development of distributed applications. Spark SQL APIs provide an optimized interface that helps developers build such applications quickly and easily. However, designing web-scale production applications using Spark SQL APIs can be a complex task. Hence, understanding the design and implementation best practices before you start your project will help you avoid these problems. This book gives an insight into the engineering practices used to design and build real-world, Spark-based applications. The book's hands-on examples will give you the required confidence to work on any future projects you encounter in Spark SQL. It starts by familiarizing you with data exploration and data munging tasks using Spark SQL and Scala. Extensive code examples will help you understand the methods used to implement typical use-cases for various types of applications. You will get a walkthrough of the key concepts and terms that are common to streaming, machine learning, and graph applications. You will also learn key performance-tuning details including Cost Based Optimization (Spark 2.2) in Spark SQL applications. Finally, you will move on to learning how such systems are architected and deployed for a successful delivery of your project.
Table of Contents (19 chapters)
Title Page
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

Understanding themes in document corpuses


Bag-of-words-based techniques can also be to classify common themes in documents or to identify themes within a corpus of documents. Broadly, these techniques, like most, are attempting to reduce the dimensionality of the term-document matrix, based on each word's relation to latent variables in this case.

One of the earliest approaches to this of classification was Latent Semantic Analysis (LSA). LSA can avoid the limitations of count-based methods associated with synonyms and terms with multiple meanings. Over the years, the concept of LSA has evolved into another model called Latent Dirichlet Allocation (LDA).

LDA allows us to identify latent thematic structure a collection of documents. Both LSA and LDA use the term-document matrix for reducing the dimensionality of the term space and for producing the topic weights. A constraint of both the LSA and LDA techniques is that they work best when applied to large documents.

Note

For more detailed explanation...