Building an ORM with Arel

Talk given at Madison Ruby 2014 with @vipulnsward

Transcript

1. Building an ORM with ARel Walking up the AS(Tree) @vipulnsward, @_cha1tanya
2. Vipul @vipulnsward && Prathamesh @_cha1tanya
4. 26 Hours
5. 48 Hours
9. RubyIndia.org
11. podcast.rubyindia.org
12. Indian Ruby Conferences RubyConfIndia Garden City Ruby Conf DeccanRubyConf Do visit India!
13. Building an ORM with ARel Walking up the (AS)Tree @vipulnsward, @_cha1tanya
15. Build our own ORM - Why?
16. Object-relational mapping (ORM, O/RM, and O/R mapping) in computer science is a programming technique for converting data between incompatible type systems in object- oriented programming languages. This creates, in effect, a "virtual object database" that can be used from within the programming language.
17. Active Record “An object that wraps a row in a database table or view, encapsulates the database access, and adds domain logic on that data.”
18. Components • Database connection • Query Generator • Attribute Access • Typecasting
19. SQL torm_development=# select * from posts; id | name | content | author | subject -----+-------------+---------+------------+--------- 332 | RGenGC| Restricted Generation Garbage Collection | GorbyPuff | How does RGenGC work? (1 row)
20. Object Post: id: 332, name: ‘RGenGC’, subject: ‘How does RGenGC work?’ content: ‘Restricted Generation Garbage Collection’ author: ‘GorbyPuff’
21. Object Post: id(int): 332, name(string): ‘RGenGC’, subject(string): ‘How does RGenGC work?’ content(string): ‘Restricted Generation Garbage Collection’ author(string): ‘GorbyPuff’
22. What? post = Post.new subject: 'What is RGenCG?' post.save first_post = Post.find(1) puts first_post.subject #=> 'What is RGenCG?'
23. How? class Post < Torm::Model … end
24. Role of ARel
25. ARel • Relational Algebra for Ruby • ARel is a SQL AST manager for Ruby • Can generate complex SQL queries • Adapts to multiple databases
26. ARel Components • AST • Visitors • Managers
27. ORM Database ARel
28. Engine • Provide information to ARel/ Attributes Access • Column / Table structure • Database Adapter • Data Type Mappings
29. Engine Skeleton
30. Database Connection
31. Columns
32. Schema Cache
33. Tests
35. Attributes • Data Types • Casting from / to database types • Attribute Maps for table • Accessors for a model
36. Types • Types • TypeMap • Attribute • AttributeSet
37. Attribute Accessors • Readers • Writes • Initializer
38. Database Statements • create • update • save • destroy
39. Querying • find • count • where • delete_all • ...
40. Summary • Database Connection • Creating columns/ Schema cache • Attribute Types/ Type casting • Attributes and accessors • Database statements • Querying
41. Other • Associations • Migrations • Callbacks • Validations • ...
42. Thank You! gh: prathamesh-sonpatki/torm @vipulnsward @_cha1tanya