Merge branch 'cache-last-commit-sha-for-path' into 'master'

Cache last commit id for path

See merge request !8098

app/models/repository.rb

@@ -654,11 +654,19 @@ class Repository
   end
   def last_commit_for_path(sha, path)
-    args = %W(#{Gitlab.config.git.bin_path} rev-list --max-count=1 #{sha} -- #{path})
-    sha = Gitlab::Popen.popen(args, path_to_repo).first.strip
+    sha = last_commit_id_for_path(sha, path)
     commit(sha)
   end
+  def last_commit_id_for_path(sha, path)
+    key = path.blank? ? "last_commit_id_for_path:#{sha}" : "last_commit_id_for_path:#{sha}:#{Digest::SHA1.hexdigest(path)}"
+
+    cache.fetch(key) do
+      args = %W(#{Gitlab.config.git.bin_path} rev-list --max-count=1 #{sha} -- #{path})
+      Gitlab::Popen.popen(args, path_to_repo).first.strip
+    end
+  end
+
   def next_branch(name, opts = {})
     branch_ids = self.branch_names.map do |n|
       next 1 if n == name

changelogs/unreleased/cache-last-commit-sha-for-path.yml

+---
+title: Cache last commit id for path
+merge_request: 8098
+author: Hiroyuki Sato

lib/api/files.rb

@@ -68,7 +68,7 @@ module API
           ref: params[:ref],
           blob_id: blob.id,
           commit_id: commit.id,
-          last_commit_id: repo.last_commit_for_path(commit.sha, params[:file_path]).id
+          last_commit_id: repo.last_commit_id_for_path(commit.sha, params[:file_path])
         }
       end

spec/models/repository_spec.rb

@@ -139,6 +139,22 @@ describe Repository, models: true do
     it { is_expected.to eq('c1acaa58bbcbc3eafe538cb8274ba387047b69f8') }
   end
+  describe '#last_commit_id_for_path' do
+    subject { repository.last_commit_id_for_path(sample_commit.id, '.gitignore') }
+
+    it "returns last commit id for a given path" do
+      is_expected.to eq('c1acaa58bbcbc3eafe538cb8274ba387047b69f8')
+    end
+
+    it "caches last commit id for a given path" do
+      cache = repository.send(:cache)
+      key = "last_commit_id_for_path:#{sample_commit.id}:#{Digest::SHA1.hexdigest('.gitignore')}"
+
+      expect(cache).to receive(:fetch).with(key).and_return('c1acaa5')
+      is_expected.to eq('c1acaa5')
+    end
+  end
+
   describe '#find_commits_by_message' do
     it 'returns commits with messages containing a given string' do
       commit_ids = repository.find_commits_by_message('submodule').map(&:id)