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Cascalog for the Impatient

Welcome to Cascalog for the Impatient, a series of blog posts and Cascalog code examples to get you started. Quickly. Like, yesterday.

Use this tutorial in conjunction with Cascading for the Impatient.

Part 1

• Implements simplest Cascalog query possible
• Copies each TSV line from source to sink
• Roughly, in about a dozen lines of code

Part 2

• Implements a simple example of WordCount
• Uses a regex to split the input text lines into a Tuple stream of tokens
• Uses a built-in Cascalog operator
• Introduction to logic programming

Part 3

• Uses a Clojure function to scrub the token stream
• Discusses when to use standard Operations vs. creating custom ones

Part 4

• Shows how to join sources together
• Filters a list of stop words out of the token stream
• Uses a Predicate Macro

Part 5

• Calculates TF-IDF by abstracting the problem into sub-queries
• Composing the results from these sub-queries into the TF-IDF formula
• Uses a special query executor for caching query result in memory

Part 6

• Includes unit tests in the build
• Use checkpoints for better performance
• Shows how to use other TDD features: assertions, traps

TO-DO

Part 6

• Shows how to use other TDD features: debug

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If you want to read in more detail about the Cascalog API which were used, see the Cascalog Wiki and JavaDoc.

For more discussion, see the cascalog-user email forum.