Cascalog - Clojure-based query language for Hadoop

Wynn Netherland Wynn Netherland

Whilst at Chirp, Wynn interviewed Mike Montano from BackType (for a new API-focused podcast we’re launching next week) and he told us about Cascalog a new Clojure-based query language for Hadoop.

Inspired by Datalog, Cascalog is a DSL in Clojure that lets the BackType team query their massive amounts of data. Since we don’t pretend to be Clojure or Hadoop nerds, I’ll let creator Nathan Marz’ blog post lay out the feature set:

  • Simple – Functions, filters, and aggregators all use the same syntax. Joins are implicit and natural.
  • Expressive – Logical composition is very powerful, and you can run arbitrary Clojure code in your query with little effort.
  • Interactive – Run queries from the Clojure REPL.
  • Scalable – Cascalog queries run as a series of MapReduce jobs.
  • Query anything – Query HDFS data, database data, and/or local data by making use of Cascading’s “Tap” abstraction
  • Careful handling of null values – Null values can make life difficult. Cascalog has a feature called “non-nullable variables” that makes dealing with nulls painless.
  • First class interoperability with Cascading – Operations defined for Cascalog can be used in a Cascading flow and vice-versa
  • First class interoperability with Clojure - Can use regular Clojure functions as operations or filters, and since Cascalog is a Clojure DSL, you can use it in other Clojure code.

If you are a Hadoop or Clojure nerd, let us know about cool projects using either, or both!

Also, this is the first Changelog post from 30,000 feet. Go go @gogoinflight!

[Source on GitHub] [Blog post]

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