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Why You Should Never Use an ORM
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John Nunemaker
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May 17, 2011
Programming
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9.2k
Why You Should Never Use an ORM
My presentation at RailsConf 2011 on thinking about your interface, your data and your code.
John Nunemaker
PRO
May 17, 2011
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Transcript
Ordered List @jnunemaker RailsConf Baltimore, MD May 17, 2011 Why
You Should Never Use an ORM
You crazy man...
None
“ Albert Einstein Any intelligent fool can make things bigger,
more complex, and more violent.
Violence My Path Of
@gem
HTTParty
HappyMapper
MongoMapper
ToyStore
None
None
Three Points
1) Interface Think About Your
1) Interface Think About Your 2) Data
1) Interface Think About Your 2) Data 3) Code
Your Interface Think About
“ John Nunemaker ORMs too often lead to interface laziness.
site.memberships.create({ :user_id => user.id, :owner => true, })
site.add_owner(user)
membership.update_attributes({ :state => 1, })
membership.update_attributes({ :state => 'maximized', })
user.maximize(site)
content.to_json({ 'a crap ton': 'of options' })
ContentPresenter.new(site, date, { :page => params['page'], }).to_json
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 # ...
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
Content.paginate({ :conditions => { :site_id => site.id, :date => date,
}, :page => params['page'], :per_page => 15, })
site.content_for_date(date, { :page => params['page'], })
Your Interface Think About
Your Data Think About
“ John Nunemaker ORMs sometimes hide creative ways you can
store and retrieve your data.
Failure and Triumph A Story of
{ '_id' => 'site_id:2011-03-28', '/' => {'v' => 200, 't'
=> 'Home'}, '/about/' => {'v' => 50, 't' => 'About'}, '/foo/' => {'v' => 23, 't' => 'Foo!'}, }
You say heresy! I say use case...
None
Content.get("#{site.id}:2011-03-28")
None
write data ensure_index(site_id, date, path)
read data ensure_index(site_id, date, views)
{ '_id' => BSON::ObjectId.new, 'sid' => site_id, 'p' => '/about/',
'd' => '2011-03-28', 'v' => 50, }
NewContent.for_site_and_date(site, date)
db['c.2011.5']
db['c.2011.5'] read index write index
db['c.2011.4'] => db['c.2011.5'] read index write index
None
/about/
/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
None
Zlib.crc32('...really long path...') 762151429
Counts Every bit
Integers
Site.create(:state => 'enabled')
class Site States = { 'enabled' => 1, 'disabled' =>
2, } end Site.create({ :state => Site::States['enabled'], })
class Site def enabled? state == States['enabled'] end def disabled?
!enabled? end end
Compression
require 'rsmaz' compressed = RSmaz.compress(str) decompressed = RSmaz.decompress(compressed)
require 'zlib' compressed = Zlib::Deflate.deflate(str) decompressed = Zlib::Inflate.inflate(compressed)
require 'msgpack' ids = [1,2,3,4,5,6,7,8,9,10] compressed = MessagePack.pack(ids) decompressed =
MessagePack.unpack(compressed)
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
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
Partial Updates
site.atomic_update_attributes(attrs)
Unused Fields
Counts Where
Memory/Disk/Network
class SiteMode include Scam attr_accessor :name def password_required? id ==
2 end def item_cache? id == 1 end end
SiteMode.create({ :id => 1, :name => 'live' }) SiteMode.all #
find by id or string id pp SiteMode.find(2) pp SiteMode.find('2')
class Plan include Toy::Store store(:memory, {}) attribute(:title, String) attribute(:price, Integer)
end
class Asset plugin Joint attachment :file def page_cache(version=nil) page_cache_original page_cache_version(version)
end end
current_user.sites.map do |site| Site.get(site['id']) end
ids = current_user.sites.map do |site| site['id'] end Site.all(:_id.in => ids)
Go A Long Way A Little Ruby Can
Move
Move BigintMove
Move BigintMove MakeYouWannaMove
Move BigintMove MakeYouWannaMove DaMove
Move BigintMove MakeYouWannaMove DaMove SmoothMove
Move BigintMove MakeYouWannaMove DaMove SmoothMove NightMove
Move BigintMove MakeYouWannaMove DaMove SmoothMove NightMove DanceMove
Partition.create({ :association => :moves, :model => Move, :first_id => 1,
:writer => false, })
Partition.for_writes.model.create(...)
Partition.since(since_id, last_move_id).map do |p| send(p.association).since(since_id) end
Your Data Think About
Your Code Think About
“ No code is faster than no code.
$ bx ruby performance/reads.rb Collection#find_one 0.270231008529663 Site.first 0.69925594329834
/track - no /content - no /referrers - no /sites
- yes /users - yes
class Hit def site @site ||= begin query = {'_id'
=> site_id} options = {:fields => ['tz']} collection.find_one(query, options) end end end
write code Don’t be afraid to
read code Don’t be afraid to
fail Don’t be afraid to
Site.find(id) Site.create({ :title => 'RailsTips', }) site.update_attributes(attrs) site.to_json
Your Code Think About
“ Albert Einstein It takes a touch of genius —and
a lot of courage—to move in the opposite direction.
Ordered List Thank you! john@orderedlist.com John Nunemaker RailsConf Baltimore, MD
May 17, 2011 @jnunemaker