From 25a868753b4b9e673af31f7f4f58f9e97811e9d9 Mon Sep 17 00:00:00 2001
From: Stan Hu <stanhu@gmail.com>
Date: Tue, 2 Jan 2018 22:52:30 -0800
Subject: [PATCH] Speed up generation of commit stats by using Rugged native
 methods

The previous implementation iterated across the entire patch set
to determine the number of lines added, deleted, and changed. Rugged
has a native method `Rugged::Diff#stat` that does this already,
which appears to be a little faster and require less RAM than doing
this ourselves.

Improves performance in #41524
---
 changelogs/unreleased/sh-optimize-commit-stats.yml | 5 +++++
 lib/gitlab/git/commit_stats.rb                     | 9 ++-------
 spec/lib/gitlab/git/commit_spec.rb                 | 5 +++++
 3 files changed, 12 insertions(+), 7 deletions(-)
 create mode 100644 changelogs/unreleased/sh-optimize-commit-stats.yml

diff --git a/changelogs/unreleased/sh-optimize-commit-stats.yml b/changelogs/unreleased/sh-optimize-commit-stats.yml
new file mode 100644
index 00000000000..8c1be1252fb
--- /dev/null
+++ b/changelogs/unreleased/sh-optimize-commit-stats.yml
@@ -0,0 +1,5 @@
+---
+title: Speed up generation of commit stats by using Rugged native methods
+merge_request:
+author:
+type: performance
diff --git a/lib/gitlab/git/commit_stats.rb b/lib/gitlab/git/commit_stats.rb
index 6bf49a0af18..8463b1eb794 100644
--- a/lib/gitlab/git/commit_stats.rb
+++ b/lib/gitlab/git/commit_stats.rb
@@ -34,13 +34,8 @@ module Gitlab
 
       def rugged_stats(commit)
         diff = commit.rugged_diff_from_parent
-
-        diff.each_patch do |p|
-          # TODO: Use the new Rugged convenience methods when they're released
-          @additions += p.stat[0]
-          @deletions += p.stat[1]
-          @total += p.changes
-        end
+        _files_changed, @additions, @deletions = diff.stat
+        @total = @additions + @deletions
       end
     end
   end
diff --git a/spec/lib/gitlab/git/commit_spec.rb b/spec/lib/gitlab/git/commit_spec.rb
index 5ed639543e0..6d35734d306 100644
--- a/spec/lib/gitlab/git/commit_spec.rb
+++ b/spec/lib/gitlab/git/commit_spec.rb
@@ -428,6 +428,11 @@ describe Gitlab::Git::Commit, seed_helper: true do
       subject { super().deletions }
       it { is_expected.to eq(6) }
     end
+
+    describe '#total' do
+      subject { super().total }
+      it { is_expected.to eq(17) }
+    end
   end
 
   describe '#stats with gitaly on' do