simplest-opendata-api.rb

class Api::OpenDataController < ApplicationController
  respond_to :xml, :json

  def sync
    records = OpenData.order(:updated_at, :id).limit(100)
    records = records.where('(updated_at, id) > (?, ?)', 
      Time.parse(params[:since]),
      params[:last_id] || 0
    ) if params[:since]
 
    if records.any?
      next_url = api_open_data_url(since: records.last.updated_at.as_json, last_id: records.last.id)        
      headers['Link'] = "<#{next_url}>; rel='next'" # Hypermedia API
    end
 
    respond_with(records)
  end
end
 
# CREATE index ON open_data (updated_at, id)