Rails ActiveRecord#select vs #pluck, 5x faster (~20k records, 10 runs each)

compare-select-pluck.rb

class Utils
  def self.compare(reports, n: 10)
    Benchmark.bm do |x|
      reports.each do |report|
        if report.is_a?(Proc)
          x.report { n.times { report.call } }
        else
          x.report(report.first) { n.times { report.last.call } }
        end
      end
    end
  end
end

Utils.compare([['select', -> { Blob.select(:id).to_a }], ['pluck', -> { Blob.pluck(:id) }]], n: 10)

       user     system      total        real
select  1.296538   0.021889   1.318427 (  1.460752)
pluck  0.184873   0.011837   0.196710 (  0.334181)