ActiveRecord: size vs count

ruby-on-rails ruby ruby-on-rails-3 rails-activerecord
Andrew picture Andrew · May 21, 2011 · Viewed 106.8k times · Source

In Rails, you can find the number of records using both Model.size and Model.count. If you're dealing with more complex queries is there any advantage to using one method over the other? How are they different?

For instance, I have users with photos. If I want to show a table of users and how many photos they have, will running many instances of user.photos.size be faster or slower than user.photos.count?

Thanks!

Answer

apneadiving picture apneadiving · May 21, 2011

You should read that, it's still valid.

You'll adapt the function you use depending on your needs.

Basically:

  • if you already load all entries, say User.all, then you should use length to avoid another db query

  • if you haven't anything loaded, use count to make a count query on your db

  • if you don't want to bother with these considerations, use size which will adapt

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