feat: eager load latest version for /pacticipants resource

Author: bethesque

db/migrations/20180828_create_latest_versions.rb

@@ -0,0 +1,25 @@
+Sequel.migration do
+  up do
+    latest_version_orders = from(:versions)
+                              .select_group(:pacticipant_id)
+                              .select_append{ max(order).as(latest_version_order) }
+
+    create_or_replace_view(:latest_version_orders, latest_version_orders)
+
+    join = {
+      Sequel[:versions][:pacticipant_id] => Sequel[:latest_version_orders][:pacticipant_id],
+      Sequel[:versions][:order] => Sequel[:latest_version_orders][:latest_version_order]
+    }
+
+    latest_versions = from(:versions)
+      .select(Sequel[:versions].*)
+      .join(:latest_version_orders, join)
+
+    create_or_replace_view(:latest_versions, latest_versions)
+  end
+
+  down do
+    drop_view(:latest_version_orders)
+    drop_view(:latest_versions)
+  end
+end

db/pact_broker_database.sqlite3

@@ -1,11 +1,11 @@
 require 'pact_broker/db'
 require 'pact_broker/messages'
 require 'pact_broker/repositories/helpers'
+require 'pact_broker/versions/latest_version'
+require 'pact_broker/domain/label'
 
 module PactBroker
-
   module Domain
-
     class Pacticipant < Sequel::Model
 
       include Messages
@@ -15,6 +15,7 @@ class Pacticipant < Sequel::Model
       one_to_many :versions, :order => :order, :reciprocal => :pacticipant
       one_to_many :labels, :order => :name, :reciprocal => :pacticipant
       one_to_many :pacts
+      one_to_one :latest_version, :class => "PactBroker::Versions::LatestVersion", primary_key: :id, key: :pacticipant_id
 
       dataset_module do
         include PactBroker::Repositories::Helpers

lib/pact_broker/domain/pacticipant.rb

@@ -23,7 +23,7 @@ def find_all
       def find options = {}
         query = PactBroker::Domain::Pacticipant.select_all_qualified
         query = query.label(options[:label_name]) if options[:label_name]
-        query.order_ignore_case(Sequel[:pacticipants][:name]).eager(:labels).all
+        query.order_ignore_case(Sequel[:pacticipants][:name]).eager(:labels).eager(:latest_version).all
       end
 
       def find_all_pacticipant_versions_in_reverse_order name

lib/pact_broker/pacticipants/repository.rb

@@ -0,0 +1,11 @@
+require 'pact_broker/domain/version'
+
+module PactBroker
+  module Versions
+    include PactBroker::Repositories::Helpers
+
+    class LatestVersion < PactBroker::Domain::Version
+      set_dataset(:latest_versions)
+    end
+  end
+end