Map vs Pluck on a collection of ActiveRecords

1 - benchmark.rb

require 'benchmark/ips'

photo = Photo.last
arr = [photo]

Benchmark.ips do |x|
  x.report('map') { arr.map(&:id) }
  x.report('pluck') { arr.pluck(:id) }
  x.compare!
end

# Warming up --------------------------------------
#                  map    99.386k i/100ms
#                pluck    43.925k i/100ms
# Calculating -------------------------------------
#                  map      1.453M (± 5.5%) i/s -      7.255M in   5.011617s
#                pluck    516.576k (± 5.5%) i/s -      2.592M in   5.034014s

# Comparison:
#                  map:  1453097.0 i/s
#                pluck:   516576.3 i/s - 2.81x  slower

2 - benchmark2.rb

# It seems weird that pluck is so much slower than map, why is this?
#
# Enumerable#pluck does this:
#
# def pluck(*keys)
#   if keys.many?
#     map { |element| keys.map { |key| element[key] } }
#   else
#     map { |element| element[keys.first] }
#   end
# end
#
# So we can benchmark calling the method directly vs calling it using a hash index:

Benchmark.ips do |x|
  x.report('method') { photo.id }
  x.report('[]') { photo[:id] }
  x.compare!
end

# Warming up --------------------------------------
#               method   107.402k i/100ms
#                   []    50.153k i/100ms
# Calculating -------------------------------------
#               method      1.701M (±12.8%) i/s -      8.377M in   5.029031s
#                   []    625.839k (± 8.9%) i/s -      3.109M in   5.012088s

# Comparison:
#               method:  1700735.1 i/s
#                   []:   625839.1 i/s - 2.72x  slower