Improve Rails perf

improve_rails_perf.md

Use pluck instead of map

Celebrity.all.map(&:id)

=> Time: 3.925s

Celebrity.select(:id).map(&:id)

=> Time: 0.098s

Celebrity.pluck(:id)

=> Time: 0.009s

Pluck is 10 times quicker !

pluck directly converts a database result into an array, without constructing ActiveRecord objects.

Use String::<< instead of String::+=

long_string = 'foo' * 10000000
long_string += 'foo'

=> Time: 0.0862s

long_string << 'foo'

=> Time: 0.00003s

Use Interpolation

long_string + long_string

=> Time: 0.20s

"#{long_string} #{long_string}"

=> Time: 0.04s