Optimize queries for snippet listings

- Avoid N+1 queries for authors and comment counts
- Avoid an additional snippet existence query

1 files changed, 29 insertions, 0 deletions

diff --git a/spec/lib/gitlab/noteable_metadata_spec.rb b/spec/lib/gitlab/noteable_metadata_spec.rb
new file mode 100644
index 00000000000..b12a1825f04
--- /dev/null
+++ b/spec/lib/gitlab/noteable_metadata_spec.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::NoteableMetadata do
+  subject { Class.new { include Gitlab::NoteableMetadata }.new }
+
+  it 'returns an empty Hash if an empty collection is provided' do
+    expect(subject.noteable_meta_data(Snippet.none, 'Snippet')).to eq({})
+  end
+
+  it 'raises an error when given a collection with no limit' do
+    expect { subject.noteable_meta_data(Snippet.all, 'Snippet') }.to raise_error(/must have a limit/)
+  end
+
+  context 'snippets' do
+    let!(:snippet) { create(:personal_snippet) }
+    let!(:other_snippet) { create(:personal_snippet) }
+    let!(:note) { create(:note, noteable: snippet) }
+
+    it 'aggregates stats on snippets' do
+      data = subject.noteable_meta_data(Snippet.all.limit(10), 'Snippet')
+
+      expect(data.count).to eq(2)
+      expect(data[snippet.id].user_notes_count).to eq(1)
+      expect(data[other_snippet.id].user_notes_count).to eq(0)
+    end
+  end
+end