array_splat_benchmark.rb

require 'benchmark'

iterations = 1_000_000

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

Benchmark.bm do |bm|

  bm.report('splatted array literal') do
    iterations.times do
      rename *[:_id, :oid]
    end
  end

  bm.report('splatted dynamic array') do
    rename_field = []
    rename_field.push :_id
    rename_field.push :oid
    iterations.times do
      rename *rename_field
    end
  end

  bm.report 'splatted array literal as eval string' do
    eval_string = "rename *[:_id, :oid]"
    iterations.times do 
      eval(eval_string, binding)
    end
  end

  bm.report('splatted dynamic array as eval string') do
    eval_string = "r = []; r.push(:_id); r.push(:oid); rename *r"
    iterations.times do
      eval(eval_string, binding)
    end
  end

end

# Results                                        user     system      total        real
# splatted array literal                     0.750000   0.020000   0.770000 (  0.777989)
# splatted dynamic array                     0.630000   0.020000   0.650000 (  0.655612)
# splatted array literal as eval string     10.870000   0.120000  10.990000 ( 11.116578)
# splatted dynamic array as eval string     17.820000   0.200000  18.020000 ( 18.261153)