array_splat_benchmark.rb

require 'benchmark'

ITERATIONS = 1_000_000

def rename(source, dest)
  { source: source, dest: dest }
end

def literal_work
  ITERATIONS.times do
    rename *[:_id, :oid]
  end
end

def dynamic_work
  rename_field = []
  rename_field << :_id
  rename_field << :oid
  ITERATIONS.times do
    rename *rename_field
  end
end

Benchmark.bm do |bm|

  bm.report('splatted array literal') do
    literal_work
  end

  bm.report('splatted dynamic array') do
    dynamic_work
  end

  bm.report 'splatted array literal as eval string' do
    eval 'literal_work'
  end

  bm.report('splatted dynamic array as eval string') do
    eval 'dynamic_work'
  end
end

# Results                              user       system     total      real
splatted array literal                 0.550000   0.020000   0.570000   (0.562727)
splatted dynamic array                 0.540000   0.020000   0.560000   (0.565917)
splatted array literal as eval string  0.550000   0.020000   0.570000   (0.564907)
splatted dynamic array as eval string  0.500000   0.020000   0.520000   (0.521945)