use multiget to minimize database calls

lib/post.rb

@@ -24,26 +24,30 @@ def initialize(params={})
 
 	class RecordNotFound < RuntimeError; end
 
-	def self.find_by_slug(slug)
-		json = DB[db_key_for_slug(slug)]
+	def self.new_from_json(json)
 		raise RecordNotFound unless json
 		new JSON.parse(json)
 	end
 
+	def self.new_from_slugs(slugs)
+		ids = slugs.map { |slug| db_key_for_slug(slug) }
+		DB.mget(ids).map { |json| new_from_json(json) }
+	end
+
+	def self.find_by_slug(slug)
+		new_from_json DB[db_key_for_slug(slug)]
+	end
+
 	def self.find_range(start, len)
-		DB.list_range(chrono_key, start, start + len - 1).map do |slug|
-			find_by_slug(slug)
-		end
+		new_from_slugs DB.list_range(chrono_key, start, start + len - 1)
 	end
 
 	def self.all
 		find_range(0, 9999999)
 	end
 
-	def self.all_tagged(tag)
-		DB.list_range("#{self}:tagged:#{tag}", 0, 99999).map do |slug|
-			find_by_slug(slug)
-		end
+	def self.find_tagged(tag)
+		new_from_slugs DB.list_range("#{self}:tagged:#{tag}", 0, 99999)
 	end
 
 	def self.db_key_for_slug(slug)

main.rb

@@ -60,7 +60,7 @@ def auth
 
 get '/past/tags/:tag' do
 	tag = params[:tag].downcase.strip
-	posts = Post.all_tagged(tag)
+	posts = Post.find_tagged(tag)
 	@title = "Posts tagged #{tag}"
 	erb :tagged, :locals => { :posts => posts, :tag => tag }
 end