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Underlaying Technology of Modern O/R Mapper
- 1. RubyKaigi2011 Underlaying Technology of Modern O/R Mappter makoto kuwata http://www.kuwata-lab.com/
- 2. Table of Contents The Goal of Modern ORM Query Object View-layer Cacing Ruby-to-SQL Transformation How to Prevent SQL Injection
- 3. The Goal of Modern ORM
- 4. What is the Problem?
- 6. Refactoring
- 7. Key Points Programming language can break large part into small pieces construct large part from small pieces add name to pieces in order to abstract them
- 8. Again, What is the Problem? • SQL can't break large one into pieces • SQL can't be constructed from pieces • SQL can't name or abstract pieces
- 9. Does ORM Solve it? Not abstracted
- 10. Abstract by Named Scope
- 11. History of Evolution OOP, Modern ORM Functional C, Pascal DBI, ORM Assembler SQL
- 12. Conclusion of this section SQL is just Assembler It can't be broken into pieces It can't be constructed from pieces It can't name or abstract pieces Modern ORM provides abstraction for SQL ex. named_scope
- 13. Query Object
- 14. Kwd arg vs. Method Chain
- 15. Query Object (1)
- 16. Query Object (2)
- 17. Method Call vs. Query Op Just a method call Operation to Query object
- 18. Query Operation (1) Just a method call
- 19. Query Operation (2) Just a method call
- 20. Query Operation (3) Just a method call
- 21. Query Operation (4) Just a method call
- 22. Query == Collection Array ActiveRecord::Relation
- 23. Action to Collection condition condition
- 27. Conslution of this section Query object is the key concept for modern ORM behaves like a collection abstracts SQL
- 28. ORM and View-layer Cache
- 30. Example: Controller Submits SQL everytime
- 31. Move find() from C to V? MVC broken
- 32. Check Cache Existence? C depends on V tightly
- 33. What is the Problem? View Cache: Pull-style MVC: Push-style Context Data Controller
- 34. Sol: Proc or Lambda (C) find(:all) is not called yet
- 35. Sol: Proc or Lambda (V) Call find(:all) only when cache is expired
- 36. Sol: Proc or Lambda Pros. Easy to understand & implement Cons. Caching on V affects to C (C must be changed according to V)
- 37. Sol: Lazy Loading (C) SQL is not executed yet
- 38. Sol: Lazy Loading (V) Nothing to be changed!
- 39. Sol: Lazy Loading Pros. Caching on V doesn't affect to C Cons. Availables only on modern ORM (not available on Rails2)
- 40. Conclusion of this section MVC and fragment cache are not good friends MVC: push-style Fragment cache: pull-style Laziness solves them Proc or lambda Lazy loading
- 41. N+1 Problem
- 42. What is N+1 Problem? (1) Team : Member = 1 : N
- 43. What is N+1 Problem? (2) }1 }N
- 45. Sol: Eager Loading Pros. Easy to understand Cons. Not adaptive to changes Easy to forget Hard to notice Unused eager loading is very waste
- 46. Sol: Strategic Eager Loading
- 47. Sol: Strategic Eager Loading • Each item knows its collection • Collection resolves relationships
- 48. Sol: Strategic Eager Loading Pros. Adaptive to changes (No need to specify relationship for eager loading) Cons. Not supported in Rails (2 & 3)
- 49. Conclusion of this section Eager loading Easy to forget, hard to notice Strategic Eager Loading No need to specify relation names Adaptive to changes
- 51. Evaluation x=1 x+1 2
- 52. AST by Evaluation x = Column.new(:x) x+1 + x 1
- 54. Ruby to AST to SQL == Operator x 1 Override
- 55. Other Examples
- 56. Sequel Example
- 57. Pitfalls 1.8 doesn't allow to override '!=' operator Use 1.9 Impossible to override '&&' nor '||' Use '&' and '|' instead, or 'AND()', 'OR()'
- 58. OT: Operast Library to convert Ruby expression into other language (such as SQL). https://github.com/kwatch/operast
- 59. OT: Oktest New-style testing library for Python Apply Operator Override to Testing http://packages.python.org/Oktest/
- 60. Conclusion of this section How to Ruby to AST (by Operator Override) AST to SQL
- 61. Any Questions?