Add sequel scope all with default scope bench

sequel/benchmarks/bm_sequel_scope_all_with_default_scope.rb

@@ -0,0 +1,46 @@
+require 'bundler/setup'
+require 'sequel'
+
+require_relative 'support/benchmark_sequel'
+
+DB = Sequel.connect(ENV.fetch('DATABASE_URL'))
+
+DB.create_table!(:users) do
+  primary_key :id
+  String :name, size: 255
+  String :email, size: 255
+  TrueClass :admin, null: false
+  DateTime :created_at, null: true
+  DateTime :updated_at, null: true
+end
+
+class User < Sequel::Model
+  dataset_module do
+    def only_admins
+      where(:admin => true)
+    end
+  end
+
+  set_dataset(self.only_admins)
+end
+
+admin = true
+
+1000.times do
+  attributes = {
+    name: "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
+    email: "foobar@email.com",
+    admin: admin
+  }
+
+  User.create(attributes)
+
+  admin = !admin
+end
+
+Benchmark.sequel("sequel/#{db_adapter}_scope_all_with_default_scope", time: 5) do
+  str = ""
+  User.all.each do |user|
+    str << "name: #{user.name} email: #{user.email}\n"
+  end
+end