CODEWITHSUNDEEP
ruby-on-railsrubyactiverecord
user1870954
user1870954

Reputation: 207

Rails 4 : ActiveRecord Delete With Offset

I have a program submitting an HTTP request to my Rails application every five minutes. These records have an index on ID & created_at to display in reverse order. Due to the frequency of these status updates, I only want to store the most recent ten of them. While researching how to do this, I figured an offset would be perfect to retrieve and then delete a dataset. Though in my rails console tests, I haven't been able to convince ActiveRecord that it wants to work that way (it deletes all of the records instead of just the ones not included in offset).

Is there a more efficient way to do what I'm trying to do in my controller? And is there a way to delete records with an offset using ActiveRecords? If not, what would be the ideal way to go about doing it?

def create
    env = Env.find_by_name(params[:updateresult][:env_name])
    @updateresult = env.updateresults.build(updateresult_params)
    respond_to do |format|
        if @updateresult.save
            format.json { render json: @updatresults, status: :created}
            #env.updateresults.where(:id => env.updateresults.offset(10).pluck(:id)).delete_all
        else
            format.json { render json: @updatresults.errors, status: :unprocessable_entity }
        end
    end
end

Edit: Altered David's answer to come up with the commented out answer in the above code

Upvotes: 0

Views: 752

Answers (1)

David Aldridge
David Aldridge

Reputation: 52376

I don't think that you can use an offset in a delete, so you'd probably have to:

delete from my_table
where id in (  select id
                 from my_table
             order by created_as desc
               offset 10);

So:

MyTable.where(:id => MyTable.order("created_at desc").offset(10).pluck(:id)).delete_all

Of course you could just delete records more than 50 minutes old?

Upvotes: 5

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