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Deterministic ordering of records by created_at timestamp

Thomas Klemm
October 24, 2014Software engineer

Creating records in specs can be so fast that two records created instantly after one another might have the same created_at timestamp (especially since those timestamps don't have an indefinitely high resolution). When ordering lists by timestamps, you should therefore always include a final order condition using the primary key of the table.

class Photo < ActiveRecord::Base
  scope :by_date, -> { order('created_at DESC, id DESC') }
end

Photo.by_date
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Remember to include the id field in the database index.

Posted by Thomas Klemm to makandra dev (2014-10-24 14:08)