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Scala for Data Science

You're reading from  Scala for Data Science

Product type Book
Published in Jan 2016
Publisher
ISBN-13 9781785281372
Pages 416 pages
Edition 1st Edition
Languages
Author (1):
Pascal Bugnion Pascal Bugnion
Profile icon Pascal Bugnion

Table of Contents (22) Chapters

Scala for Data Science
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
1. Scala and Data Science 2. Manipulating Data with Breeze 3. Plotting with breeze-viz 4. Parallel Collections and Futures 5. Scala and SQL through JDBC 6. Slick – A Functional Interface for SQL 7. Web APIs 8. Scala and MongoDB 9. Concurrency with Akka 10. Distributed Batch Processing with Spark 11. Spark SQL and DataFrames 12. Distributed Machine Learning with MLlib 13. Web APIs with Play 14. Visualization with D3 and the Play Framework Pattern Matching and Extractors Index

Casbah query DSL


Using DBObject instances to express queries can be very verbose and somewhat difficult to read. Casbah provides a DSL to express queries much more succinctly. For instance, to get all the documents with the github_id field between 20 and 30, we would write the following:

scala> collection.find("github_id" $gte 20 $lt 30).toList
List[com.mongodb.casbah.Imports.DBObject] = List({ "_id" : { "$oid" : "562e922546f953739c43df0f"} , "github_id" : 23 , "login" : "takeo" , "repos" : ...

The operators provided by the DSL will automatically construct DBObject instances. Using the DSL operators as much as possible generally leads to much more readable and maintainable code.

Going into the full details of the query DSL is beyond the scope of this chapter. You should find it quite easy to use. For a full list of the operators supported by the DSL, refer to the Casbah documentation at http://mongodb.github.io/casbah/3.0/reference/query_dsl/. We summarize the most important operators...

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