Active Record No NosUse your common sense

About me

Patrick Hüsler

Freelance developer

Apple enthusiast

Surfing and Kung Fu

AR Kool AidNo giant xml mapping file

Dynamic finders

Associations

Inheritance

Polymorphism

...

IT’S ALMOST WIZARDRY!!!!

BUT...

SO...

Be reasonable or ...

Code like this

@user.friends.map {|friend| friend.id}

Or this

@user.friends.sort_by{ |friend| [ friend.online? ? 1 : 0,friend] }

Or this

friends.accepted.map{ |friend| friend.logs.visible_for(self) }.flatten

eventually leads to

THIS

We can do better ...

Look at the generated SQL

Create indices

Let AR/SQL do the math (conditions,count,sum, named_scope, ...)

Paginate, but paginate in SQL not on ruby collections

Only fetch what you really need (:select => :id)

Use :include (n + 1 problem)

Check SQL logs

tail -f log/*.log

Log to STDOUT in script/console

Do it once in ~/.irbrc

Use one of the query analyzer plugins

Use profiling tools like New Relic RPM, FiveRuns TuneUp or Rack::Bug (Check railscast)

Where to look

Iterations/calculations in views / partials

Calculations on potentially big collections in ruby that can be done in SQL

@user.friends.recent.sort_by{ |friend| [ friend.online? ? 1 : 0,friend] }

Pagination on collection instead of SQL

User.all.paginate(:per_page => 1, :page => 1)

Where to lookNot eager loaded associations

Post.all.each{|post| puts post.author.name}

Classic n + 1 problem

Post.all(:include => :author)

Ruby is used for tasks that could be done with SQL

Post.all.map(&:id)

Instead of Post.all(:select => :id)

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Available for hire

patrick.huesler@gmail.com

https://www.xing.com/profile/Patrick_Huesler

http://twitter.com/phuesler

http://github.com/phuesler

Contact info