Why You Should Never Use an ORM

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Ordered List @jnunemaker RailsConf Baltimore, MD May 17, 2011 Why You Should Never Use an ORM

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You crazy man...

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“ Albert Einstein Any intelligent fool can make things bigger, more complex, and more violent.

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Violence My Path Of

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@gem

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HTTParty

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HappyMapper

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MongoMapper

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ToyStore

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Three Points

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1) Interface Think About Your

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1) Interface Think About Your 2) Data

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1) Interface Think About Your 2) Data 3) Code

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Your Interface Think About

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“ John Nunemaker ORMs too often lead to interface laziness.

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site.memberships.create({ :user_id => user.id, :owner => true, })

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site.add_owner(user)

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membership.update_attributes({ :state => 1, })

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membership.update_attributes({ :state => 'maximized', })

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user.maximize(site)

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content.to_json({ 'a crap ton': 'of options' })

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ContentPresenter.new(site, date, { :page => params['page'], }).to_json

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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 # ...

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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

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Content.paginate({ :conditions => { :site_id => site.id, :date => date, }, :page => params['page'], :per_page => 15, })

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site.content_for_date(date, { :page => params['page'], })

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Your Interface Think About

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Your Data Think About

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“ John Nunemaker ORMs sometimes hide creative ways you can store and retrieve your data.

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Failure and Triumph A Story of

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{ '_id' => 'site_id:2011-03-28', '/' => {'v' => 200, 't' => 'Home'}, '/about/' => {'v' => 50, 't' => 'About'}, '/foo/' => {'v' => 23, 't' => 'Foo!'}, }

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You say heresy! I say use case...

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Content.get("#{site.id}:2011-03-28")

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write data ensure_index(site_id, date, path)

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read data ensure_index(site_id, date, views)

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{ '_id' => BSON::ObjectId.new, 'sid' => site_id, 'p' => '/about/', 'd' => '2011-03-28', 'v' => 50, }

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NewContent.for_site_and_date(site, date)

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db['c.2011.5']

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db['c.2011.5'] read index write index

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db['c.2011.4'] => db['c.2011.5'] read index write index

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/about/

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/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

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Zlib.crc32('...really long path...') 762151429

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Counts Every bit

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Integers

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Site.create(:state => 'enabled')

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class Site States = { 'enabled' => 1, 'disabled' => 2, } end Site.create({ :state => Site::States['enabled'], })

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class Site def enabled? state == States['enabled'] end def disabled? !enabled? end end

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Compression

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require 'rsmaz' compressed = RSmaz.compress(str) decompressed = RSmaz.decompress(compressed)

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require 'zlib' compressed = Zlib::Deflate.deflate(str) decompressed = Zlib::Inflate.inflate(compressed)

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require 'msgpack' ids = [1,2,3,4,5,6,7,8,9,10] compressed = MessagePack.pack(ids) decompressed = MessagePack.unpack(compressed)

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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

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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

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Partial Updates

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site.atomic_update_attributes(attrs)

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Unused Fields

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Counts Where

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Memory/Disk/Network

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class SiteMode include Scam attr_accessor :name def password_required? id == 2 end def item_cache? id == 1 end end

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SiteMode.create({ :id => 1, :name => 'live' }) SiteMode.all # find by id or string id pp SiteMode.find(2) pp SiteMode.find('2')

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class Plan include Toy::Store store(:memory, {}) attribute(:title, String) attribute(:price, Integer) end

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class Asset plugin Joint attachment :file def page_cache(version=nil) page_cache_original page_cache_version(version) end end

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current_user.sites.map do |site| Site.get(site['id']) end

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ids = current_user.sites.map do |site| site['id'] end Site.all(:_id.in => ids)

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Go A Long Way A Little Ruby Can

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Move

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Move BigintMove

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Move BigintMove MakeYouWannaMove

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Move BigintMove MakeYouWannaMove DaMove

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Move BigintMove MakeYouWannaMove DaMove SmoothMove

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Move BigintMove MakeYouWannaMove DaMove SmoothMove NightMove

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Move BigintMove MakeYouWannaMove DaMove SmoothMove NightMove DanceMove

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Partition.create({ :association => :moves, :model => Move, :first_id => 1, :writer => false, })

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Partition.for_writes.model.create(...)

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Partition.since(since_id, last_move_id).map do |p| send(p.association).since(since_id) end

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Your Data Think About

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Your Code Think About

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“ No code is faster than no code.

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$ bx ruby performance/reads.rb Collection#ﬁnd_one 0.270231008529663 Site.ﬁrst 0.69925594329834

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/track - no /content - no /referrers - no /sites - yes /users - yes

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class Hit def site @site ||= begin query = {'_id' => site_id} options = {:fields => ['tz']} collection.find_one(query, options) end end end

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write code Don’t be afraid to

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read code Don’t be afraid to

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fail Don’t be afraid to

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Site.find(id) Site.create({ :title => 'RailsTips', }) site.update_attributes(attrs) site.to_json

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Your Code Think About

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“ Albert Einstein It takes a touch of genius —and a lot of courage—to move in the opposite direction.

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Ordered List Thank you! [email protected] John Nunemaker RailsConf Baltimore, MD May 17, 2011 @jnunemaker