reject.rb

require 'set'
require 'benchmark'

def reject_this_set(list, ids)
  order_set = Set.new
  ids.each { |i| order_set << i }
  list.reject { |val| order_set.include?(val[:order_id]) }
end

def reject_this(list, ids)
  list.reject { |val| ids.include?(val[:order_id]) }
end


fake_orders = []
1_000_000.times do |i|
  fake_orders << { order_id: i.to_s, name: "John #{i}" }
end

fake_order_ids = (1..100_000).to_a.sample(5_000)

Benchmark.bm do |bm|
  bm.report { reject_this(fake_orders, fake_order_ids) }
  bm.report { reject_this(fake_orders, fake_order_ids) }
end