arel_talk_notes.md

Here's the gist of the step-wise refactoring done during the talk. Included below are some specific links that were insightful to me as I dug in to this.

Modern Resources

• A RailsConf 2014 Presentation from the creator of Scuttle, a tool for automatically generating Arel from a SQL query
• The Definitive Guide to Arel—a blog post giving a great overview of Arel's functionality
• O'Reilly gives an intro to Arel and then a deeper dive
• Arel Helpers is a gem that provides some syntactic sugar for interacting with Arel.
• Some nice sample code showing how Arel can be used well.

Historical Information

• Nick Kallen, original author, explains the origins of Arel
• Arel being originally introduced on Rails Dispatch, where it is described as ActiveRelation
• Ernie Miller clearing up the difference in Arel and ActiveRecord::Relation

Reference

• Arel on Github
• Relational Algebra on Wikipedia
• A Relational Model of Data for Large Shared Data Banks
• Abstract Syntax Trees on Wikipedia
• Ruby ASTs by Ilya Grigorik
• The Visitor Pattern on Wikipedia
• Variations on the Visitor Pattern, where the extrinsic visitor is introduced
• Aaron Patterson on double dispatch in Ruby