Why You Should Never Use an ORM

My presentation at RailsConf 2011 on thinking about your interface, your data and your code.

Transcript

1. Ordered List @jnunemaker RailsConf Baltimore, MD May 17, 2011 Why You Should Never Use an ORM
2. You crazy man...
4. “ Albert Einstein Any intelligent fool can make things bigger, more complex, and more violent.
5. Violence My Path Of
6. @gem
7. HTTParty
8. HappyMapper
9. MongoMapper
10. ToyStore
13. Three Points
14. 1) Interface Think About Your
15. 1) Interface Think About Your 2) Data
16. 1) Interface Think About Your 2) Data 3) Code
17. Your Interface Think About
18. “ John Nunemaker ORMs too often lead to interface laziness.
19. site.memberships.create({ :user_id => user.id, :owner => true, })
20. site.add_owner(user)
21. membership.update_attributes({ :state => 1, })
22. membership.update_attributes({ :state => 'maximized', })
23. user.maximize(site)
24. content.to_json({ 'a crap ton': 'of options' })
25. ContentPresenter.new(site, date, { :page => params['page'], }).to_json
26. class ContentPresenter include BasePresenter def initialize(site, date, options={}) @site, @date = site, date @options = options end def page # ... def per_page # ... def total # ... def path # ... def prev_path # ... def next_path # ... def next_page_path # ... def prev_page_path # ... def paginated # ... def content # ...
27. def path # ... def prev_path # ... def next_path # ... def next_page_path # ... def prev_page_path # ... def paginated # ... def content # ... def as_json(options = nil) { 'date' => @date.to_s, 'prev_path' => prev_path, 'next_path' => next_path, 'content' => content, 'page' => page, 'per_page' => per_page, 'total' => total, 'prev_page_path' => prev_page_path, 'next_page_path' => next_page_path, } end end
28. Content.paginate({ :conditions => { :site_id => site.id, :date => date, }, :page => params['page'], :per_page => 15, })
29. site.content_for_date(date, { :page => params['page'], })
30. Your Interface Think About
31. Your Data Think About
32. “ John Nunemaker ORMs sometimes hide creative ways you can store and retrieve your data.
33. Failure and Triumph A Story of
34. { '_id' => 'site_id:2011-03-28', '/' => {'v' => 200, 't' => 'Home'}, '/about/' => {'v' => 50, 't' => 'About'}, '/foo/' => {'v' => 23, 't' => 'Foo!'}, }
35. You say heresy! I say use case...
37. Content.get("#{site.id}:2011-03-28")
39. write data ensure_index(site_id, date, path)
40. read data ensure_index(site_id, date, views)
41. { '_id' => BSON::ObjectId.new, 'sid' => site_id, 'p' => '/about/', 'd' => '2011-03-28', 'v' => 50, }
42. NewContent.for_site_and_date(site, date)
43. db['c.2011.5']
44. db['c.2011.5'] read index write index
45. db['c.2011.4'] => db['c.2011.5'] read index write index
47. /about/
48. /this/is/my/really/long/ and/descriptive/path/and/ of/course/we/need/to/ have/a/query/string? gibberish=true&yunolikesh orturls=false#DontForgetT oHashTagIt
50. Zlib.crc32('...really long path...') 762151429
51. Counts Every bit
52. Integers
53. Site.create(:state => 'enabled')
54. class Site States = { 'enabled' => 1, 'disabled' => 2, } end Site.create({ :state => Site::States['enabled'], })
55. class Site def enabled? state == States['enabled'] end def disabled? !enabled? end end
56. Compression
57. require 'rsmaz' compressed = RSmaz.compress(str) decompressed = RSmaz.decompress(compressed)
58. require 'zlib' compressed = Zlib::Deflate.deflate(str) decompressed = Zlib::Inflate.inflate(compressed)
59. require 'msgpack' ids = [1,2,3,4,5,6,7,8,9,10] compressed = MessagePack.pack(ids) decompressed = MessagePack.unpack(compressed)
60. class Stylesheet class RSmazCompressor def self.compress(str) RSmaz.compress(str) end def self.decompress(str) RSmaz.decompress(str) end end class ZlibCompressor def self.compress(str) Zlib::Deflate.deflate(str) end def self.decompress(str) Zlib::Deflate.inflate(str) end end
61. Compressors = { 1 => RSmazCompressor, 2 => ZlibCompressor, } key :compressor_id, Integer key :contents, String validates_inclusion_of :compressor_id, :within => Compressors.keys def contents value = read_attribute(:contents) compressor.decompress(value) end def compressor Compressors[compressor_id] end end
62. Partial Updates
63. site.atomic_update_attributes(attrs)
64. Unused Fields
65. Counts Where
66. Memory/Disk/Network
67. class SiteMode include Scam attr_accessor :name def password_required? id == 2 end def item_cache? id == 1 end end
68. SiteMode.create({ :id => 1, :name => 'live' }) SiteMode.all # find by id or string id pp SiteMode.find(2) pp SiteMode.find('2')
69. class Plan include Toy::Store store(:memory, {}) attribute(:title, String) attribute(:price, Integer) end
70. class Asset plugin Joint attachment :file def page_cache(version=nil) page_cache_original page_cache_version(version) end end
71. current_user.sites.map do |site| Site.get(site['id']) end
72. ids = current_user.sites.map do |site| site['id'] end Site.all(:_id.in => ids)
73. Go A Long Way A Little Ruby Can
74. Move
75. Move BigintMove
76. Move BigintMove MakeYouWannaMove
77. Move BigintMove MakeYouWannaMove DaMove
78. Move BigintMove MakeYouWannaMove DaMove SmoothMove
79. Move BigintMove MakeYouWannaMove DaMove SmoothMove NightMove
80. Move BigintMove MakeYouWannaMove DaMove SmoothMove NightMove DanceMove
81. Partition.create({ :association => :moves, :model => Move, :first_id => 1, :writer => false, })
82. Partition.for_writes.model.create(...)
83. Partition.since(since_id, last_move_id).map do |p| send(p.association).since(since_id) end
84. Your Data Think About
85. Your Code Think About
86. “ No code is faster than no code.
87. $ bx ruby performance/reads.rb Collection#find_one 0.270231008529663 Site.first 0.69925594329834
88. /track - no /content - no /referrers - no /sites - yes /users - yes
89. class Hit def site @site ||= begin query = {'_id' => site_id} options = {:fields => ['tz']} collection.find_one(query, options) end end end
90. write code Don’t be afraid to
91. read code Don’t be afraid to
92. fail Don’t be afraid to
93. Site.find(id) Site.create({ :title => 'RailsTips', }) site.update_attributes(attrs) site.to_json
94. Your Code Think About
95. “ Albert Einstein It takes a touch of genius —and a lot of courage—to move in the opposite direction.
96. Ordered List Thank you! john@orderedlist.com John Nunemaker RailsConf Baltimore, MD May 17, 2011 @jnunemaker