Iterating through every record in a database - Ruby on Rails / ActiveRecord

Question

n00b question. I'm trying to loop through every User record in my database. The pseudo code might look a little something like this:

def send_notifications

        render :nothing => true

        # Randomly select Message record from DB
        @message = Message.offset(rand(Message.count)).first

        random_message = @message.content

        @user = User.all.entries.each do
            @user = User.find(:id)

            number_to_text = ""

            @user.number = number_to_text #number is a User's phone number
            puts @user.number

        end

    end

Can someone fill me in on the best approach for doing this? A little help with the syntax would be great too :)

can we get a bit more background on what you are trying to achieve. Going through you user database this way seems a bit overhead — toxicate20
– toxicate20, Commented Nov 18, 2012 at 16:35
It's better if you get a basic knowledge in Ruby. You will not regret it , for sure . Anyway , tell us what is the purpose if the loop ? — R Milushev
– R Milushev, Commented Nov 18, 2012 at 16:40
Sending an SMS to every user in the the DB. 'number' = a User's phone number. — dougiebuckets
– dougiebuckets, Commented Nov 18, 2012 at 16:45
updated the post with all of the controller's code to give more context. — dougiebuckets
– dougiebuckets, Commented Nov 18, 2012 at 17:15

Jim U · Accepted Answer · 2021-10-21 22:28:23Z

84

Here is the correct syntax to iterate over all User :

User.all.each do |user|
  #the code here is called once for each user
  # user is accessible by 'user' variable

  # WARNING: User.all performs poorly with large datasets
end

To improve performance and decrease load, use User.find_each (see doc) instead of User.all. Note that using find_each loses the ability to sort.

edited Oct 21, 2021 at 22:28

Jim U

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answered Nov 18, 2012 at 17:53

Adrien Coquio

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W4rQCC1yGh · Accepted Answer · 2015-09-30 10:13:23Z

1

Also a possible one-liner for same purpose:

User.all.map { |u| u.number = ""; puts u.number }

answered Sep 30, 2015 at 10:13

W4rQCC1yGh

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