Use a specialized class for querying events

This changes various controllers to use the new EventCollection class
for retrieving events. This class uses a JOIN LATERAL query on
PostgreSQL to retrieve queries in a more efficient way, while falling
back to a simpler / less efficient query for MySQL.

The EventCollection class also includes a limit on the number of events
to display to prevent malicious users from cycling through all events,
as doing so could put a lot of pressure on the database.

JOIN LATERAL is only supported on PostgreSQL starting with version 9.3.0
and as such this optimisation is only used when using PostgreSQL 9.3 or
newer.

1 files changed, 51 insertions, 0 deletions

diff --git a/spec/models/event_collection_spec.rb b/spec/models/event_collection_spec.rb
new file mode 100644
index 00000000000..e0a87c18cc7
--- /dev/null
+++ b/spec/models/event_collection_spec.rb
@@ -0,0 +1,51 @@
+require 'spec_helper'
+
+describe EventCollection do
+  describe '#to_a' do
+    let(:project) { create(:project_empty_repo) }
+    let(:projects) { Project.where(id: project.id) }
+    let(:user) { create(:user) }
+
+    before do
+      20.times do
+        event = create(:push_event, project: project, author: user)
+
+        create(:push_event_payload, event: event)
+      end
+
+      create(:closed_issue_event, project: project, author: user)
+    end
+
+    it 'returns an Array of events' do
+      events = described_class.new(projects).to_a
+
+      expect(events).to be_an_instance_of(Array)
+    end
+
+    it 'applies a limit to the number of events' do
+      events = described_class.new(projects).to_a
+
+      expect(events.length).to eq(20)
+    end
+
+    it 'can paginate through events' do
+      events = described_class.new(projects, offset: 20).to_a
+
+      expect(events.length).to eq(1)
+    end
+
+    it 'returns an empty Array when crossing the maximum page number' do
+      events = described_class.new(projects, limit: 1, offset: 15).to_a
+
+      expect(events).to be_empty
+    end
+
+    it 'allows filtering of events using an EventFilter' do
+      filter = EventFilter.new(EventFilter.issue)
+      events = described_class.new(projects, filter: filter).to_a
+
+      expect(events.length).to eq(1)
+      expect(events[0].action).to eq(Event::CLOSED)
+    end
+  end
+end