big speedup in syncing via caching/reducing queries (#610)

app/models/article.rb

@@ -154,7 +154,7 @@ class Article < ActiveRecord::Base
   # to get the correspondent shared article
   def shared_article(supplier = self.supplier)
     self.order_number.blank? and return nil
-    @shared_article ||= supplier.shared_supplier.shared_articles.find_by_number(self.order_number) rescue nil
+    @shared_article ||= supplier.shared_supplier.find_article_by_number(self.order_number) rescue nil
   end
 
   # convert units in foodcoop-size

app/models/shared_supplier.rb

@@ -8,6 +8,16 @@ class SharedSupplier < ActiveRecord::Base
   has_many :suppliers
   has_many :shared_articles, :foreign_key => :supplier_id
 
+
+  def find_article_by_number(order_number)
+    # note that `shared_articles` uses number instead order_number
+    cached_articles.detect { |a| a.number == order_number }
+  end
+
+  def cached_articles
+    @cached_articles ||= shared_articles.all
+  end
+
   # These set of attributes are used to autofill attributes of new supplier,
   # when created by import from shared supplier feature.
   def autofill_attributes

app/models/supplier.rb

@@ -32,11 +32,13 @@ class Supplier < ActiveRecord::Base
   # also returns an array with new articles, which should be added (depending on shared_sync_method)
   def sync_all
     updated_article_pairs, outlisted_articles, new_articles = [], [], []
+    existing_articles = Set.new
     for article in articles.undeleted
       # try to find the associated shared_article
       shared_article = article.shared_article(self)
 
       if shared_article # article will be updated
+        existing_articles.add(shared_article.id)
         unequal_attributes = article.shared_article_changed?(self)
         unless unequal_attributes.blank? # skip if shared_article has not been changed
           article.attributes = unequal_attributes
@@ -51,11 +53,11 @@ class Supplier < ActiveRecord::Base
     end
     # Find any new articles, unless the import is manual
     unless shared_sync_method == 'import'
-      for shared_article in shared_supplier.shared_articles
-        unless articles.undeleted.find_by_order_number(shared_article.number)
-          new_articles << shared_article.build_new_article(self)
-        end
-      end
+      shared_supplier
+        .shared_articles
+        .where(available: true)
+        .where.not(id: existing_articles)
+        .each { |shared_article| new_articles << shared_article.build_new_article(self) }
     end
     return [updated_article_pairs, outlisted_articles, new_articles]
   end