How to download CSV data using ActionController::Live from MongoDB?

Mongoid automatically query your records in batches (More info over here)

To add your records to a CSV file, you should do something like:

records = MyModel.all# By default batch_size is 100, but you can modify it using .batch_size(x)result = CSV.generate do |csv|  csv << ["attribute1", "attribute2", ...]  records.each do |r|    csv << [r.attribute1, r.attribute2, ...]  endendsend_data result, filename: 'MyCsv.csv'

Remember that send_data is an ActionController method!

I think you don´t need SSE for generating a CSV. Just include ActionController::Live into the controller to use the response.stream.write iterating your collection:

include ActionController::Live...def some_action  format.csv do    # Needed for streaming to workaround Rack 2.2 bug    response.headers['Last-Modified'] = Time.now.httpdate    headers['Content-Disposition'] = "attachment; filename=\"products.csv\""    headers['Content-Type'] ||= 'text/csv'    [1,2,3,4].each do |i|   # --> change it to iterate your DB records      response.stream.write ['SOME', 'thing', "interesting #{i}", "#{Time.zone.now}"].to_csv      sleep 1  # some fake delay to see chunking    end    ensure      response.stream.close    end  end

Try it with curl or similar to see the output line by line:

$ curl -i  http://localhost:3000/test.csv