From e94358798d85b355865ce21a04cdead90fa6f7ed Mon Sep 17 00:00:00 2001
From: Toby Lawrence <tlawrence@edx.org>
Date: Tue, 23 Aug 2016 15:13:16 -0400
Subject: [PATCH] Try plucking instead of mapping.

Use pluck instead of map for upvoted/downvoted IDs.

Mapping involves doing the projection locally, whereas plucking will ask
MongoDB to do the projection for us.  This is the difference between
sending the whole document back and sending back the ObjectId itself.

Multipled against hundreds or thousands of documents, mapping can really
add up, so plucking should really help these 99%'ile cases.
---
 models/user.rb           |  4 ++--
 spec/api/user_spec.rb    | 25 ++++++++++++++++++++++++-
 spec/models/user_spec.rb | 22 ++++++++++++++++++++++
 spec/spec_helper.rb      | 11 +++++++++++
 4 files changed, 59 insertions(+), 3 deletions(-)
 create mode 100644 spec/models/user_spec.rb

diff --git a/models/user.rb b/models/user.rb
index 05fd142..48443fa 100644
--- a/models/user.rb
+++ b/models/user.rb
@@ -111,11 +111,11 @@ class User
   end
 
   def upvoted_ids
-    Content.up_voted_by(self).map(&:id)
+    Content.up_voted_by(self).pluck(:_id)
   end
 
   def downvoted_ids
-    Content.down_voted_by(self).map(&:id)
+    Content.down_voted_by(self).pluck(:_id)
   end
 
   def followers
diff --git a/spec/api/user_spec.rb b/spec/api/user_spec.rb
index 1346d05..e43bcb9 100644
--- a/spec/api/user_spec.rb
+++ b/spec/api/user_spec.rb
@@ -42,10 +42,15 @@ describe "app" do
       end
       it "returns error if new information has conflict with other users" do
         put "/api/v1/users/1", username: "user2"
-        last_response.status.should == 400 
+        last_response.status.should == 400
       end
     end
+
     describe "GET /api/v1/users/:user_id" do
+      let(:author) { User.find_by(external_id: "1") }
+      let(:reader) { User.find_by(external_id: "2") }
+      let(:thread) { make_standalone_thread(author) }
+
       it "returns user information" do
         get "/api/v1/users/1"
         last_response.status.should == 200
@@ -54,10 +59,28 @@ describe "app" do
         res["external_id"].should == user1.external_id
         res["username"].should == user1.username
       end
+
       it "returns 404 if user does not exist" do
         get "/api/v1/users/3"
         last_response.status.should == 404
       end
+
+      it "returns no threads when user hasn't voted" do
+        get "/api/v1/users/1", complete: "true"
+        last_response.status.should == 200
+        res = parse(last_response.body)
+        res["upvoted_ids"].should == []
+      end
+
+      it "returns threads when user votes" do
+        reader.vote(thread, :up)
+
+        get "/api/v1/users/2", complete: "true"
+        last_response.status.should == 200
+        res = parse(last_response.body)
+        res["upvoted_ids"].should == [thread.id.to_s]
+      end
+
       describe "Returns threads_count and comments_count" do
           before(:each) { setup_10_threads }
 
diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
new file mode 100644
index 0000000..3077bdc
--- /dev/null
+++ b/spec/models/user_spec.rb
@@ -0,0 +1,22 @@
+require 'spec_helper'
+require 'unicode_shared_examples'
+
+describe User do
+  let(:author) { create_test_user(666) }
+  let(:reader) { create_test_user(667) }
+  let(:thread) { make_standalone_thread(author) }
+
+  before(:each) do
+    [Comment, CommentThread, User].each(&:delete_all).each(&:remove_indexes).each(&:create_indexes)
+  end
+
+  it "should have no votes if it never voted" do
+    reader.upvoted_ids.should == []
+  end
+
+  it "should have one vote if it voted once" do
+    reader.upvoted_ids.should == []
+    reader.vote(thread, :up)
+    reader.upvoted_ids.should == [thread._id]
+  end
+end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index cab9804..77eab93 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -342,6 +342,17 @@ def make_comment(author, parent, text)
   comment
 end
 
+def make_standalone_thread(author)
+  make_thread(
+      author,
+      "standalone thread 0",
+      DFLT_COURSE_ID,
+      "pdq",
+      :discussion,
+      :standalone
+  )
+end
+
 # add standalone threads and comments to the @threads and @comments hashes
 # using the namespace "standalone t#{index}" for threads and "standalone t#{index} c#{i}" for comments
 # takes an index param if used within an iterator, otherwise will namespace using 0 for thread index