Refactor Gitlab::SearchResults

Instead of plucking IDs this class now uses ActiveRecord::Relation
objects. Plucking IDs is problematic as searching for projects can lead
to a huge amount of IDs being loaded into memory only to be used as an
argument for another query (instead of just using a sub-query).

app/services/search/global_service.rb

@@ -10,9 +10,8 @@ module Search
       group = Group.find_by(id: params[:group_id]) if params[:group_id].present?
       projects = ProjectsFinder.new.execute(current_user)
       projects = projects.in_namespace(group.id) if group
-      project_ids = projects.pluck(:id)
 
-      Gitlab::SearchResults.new(project_ids, params[:search])
+      Gitlab::SearchResults.new(projects, params[:search])
     end
   end
 end

lib/gitlab/search_results.rb

@@ -2,12 +2,12 @@ module Gitlab
   class SearchResults
     attr_reader :query
 
-    # Limit search results by passed project ids
+    # Limit search results by passed projects
     # It allows us to search only for projects user has access to
-    attr_reader :limit_project_ids
+    attr_reader :limit_projects
 
-    def initialize(limit_project_ids, query)
+    def initialize(limit_projects, query)
-      @limit_project_ids = limit_project_ids || Project.all
+      @limit_projects = limit_projects || Project.all
       @query = Shellwords.shellescape(query) if query.present?
     end
 
@@ -27,7 +27,8 @@ module Gitlab
     end
 
     def total_count
-      @total_count ||= projects_count + issues_count + merge_requests_count + milestones_count
+      @total_count ||= projects_count + issues_count + merge_requests_count +
+        milestones_count
     end
 
     def projects_count
@@ -53,27 +54,29 @@ module Gitlab
     private
 
     def projects
-      Project.where(id: limit_project_ids).search(query)
+      limit_projects.search(query)
     end
 
     def issues
-      issues = Issue.where(project_id: limit_project_ids)
+      issues = Issue.where(project_id: project_ids_relation)
+
       if query =~ /#(\d+)\z/
         issues = issues.where(iid: $1)
       else
         issues = issues.full_search(query)
       end
+
       issues.order('updated_at DESC')
     end
 
     def milestones
-      milestones = Milestone.where(project_id: limit_project_ids)
+      milestones = Milestone.where(project_id: project_ids_relation)
       milestones = milestones.search(query)
       milestones.order('updated_at DESC')
     end
 
     def merge_requests
-      merge_requests = MergeRequest.in_projects(limit_project_ids)
+      merge_requests = MergeRequest.in_projects(project_ids_relation)
       if query =~ /[#!](\d+)\z/
         merge_requests = merge_requests.where(iid: $1)
       else
@@ -89,5 +92,9 @@ module Gitlab
     def per_page
       20
     end
+
+    def project_ids_relation
+      limit_projects.select(:id)
+    end
   end
 end

spec/lib/gitlab/search_results_spec.rb

@@ -0,0 +1,55 @@
+require 'spec_helper'
+
+describe Gitlab::SearchResults do
+  let!(:project) { create(:project, name: 'foo') }
+  let!(:issue) { create(:issue, project: project, title: 'foo') }
+
+  let!(:merge_request) do
+    create(:merge_request, source_project: project, title: 'foo')
+  end
+
+  let!(:milestone) { create(:milestone, project: project, title: 'foo') }
+  let(:results) { described_class.new(Project.all, 'foo') }
+
+  describe '#total_count' do
+    it 'returns the total amount of search hits' do
+      expect(results.total_count).to eq(4)
+    end
+  end
+
+  describe '#projects_count' do
+    it 'returns the total amount of projects' do
+      expect(results.projects_count).to eq(1)
+    end
+  end
+
+  describe '#issues_count' do
+    it 'returns the total amount of issues' do
+      expect(results.issues_count).to eq(1)
+    end
+  end
+
+  describe '#merge_requests_count' do
+    it 'returns the total amount of merge requests' do
+      expect(results.merge_requests_count).to eq(1)
+    end
+  end
+
+  describe '#milestones_count' do
+    it 'returns the total amount of milestones' do
+      expect(results.milestones_count).to eq(1)
+    end
+  end
+
+  describe '#empty?' do
+    it 'returns true when there are no search results' do
+      allow(results).to receive(:total_count).and_return(0)
+
+      expect(results.empty?).to eq(true)
+    end
+
+    it 'returns false when there are search results' do
+      expect(results.empty?).to eq(false)
+    end
+  end
+end