Add system check for missing database indexes (#30888)

spec/lib/admin/db/schema_parser_spec.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe Admin::Db::SchemaParser do
+  let(:dummy_schema) do
+    <<~SCHEMA
+      # Comment
+      ActiveRecord::Schema[7.1].define(version: 23) do
+        create_table "people", force: :cascade do |t|
+          t.string "name"
+        end
+
+        create_table "posts", force: :cascade do |t|
+          t.string "title", null: false
+          t.bigint "size", null: false
+          t.string "description"
+          # t.index ["size", "title"], name: "index_posts_on_size_and_title"
+          t.index ["title"], name: "index_posts_on_title", unique: true
+          t.index ["size"], name: "index_posts_on_size"
+        end
+
+        # add_index "people", ["name"], name: "commented_out_index"
+        add_index "people", ["name"], name: "index_people_on_name"
+      end
+    SCHEMA
+  end
+  let(:schema_parser) { described_class.new(dummy_schema) }
+
+  describe '#indexes_by_table' do
+    subject { schema_parser.indexes_by_table }
+
+    it 'returns index info for all affected tables' do
+      expect(subject.keys).to match_array(%w(people posts))
+    end
+
+    it 'returns all index information for the `people` table' do
+      people_info = subject['people']
+      expect(people_info.map(&:name)).to contain_exactly('index_people_on_name')
+    end
+
+    it 'returns all index information for the `posts` table' do
+      posts_info = subject['posts']
+      expect(posts_info.map(&:name)).to contain_exactly(
+        'index_posts_on_title', 'index_posts_on_size'
+      )
+    end
+  end
+end

spec/lib/admin/system_check/missing_indexes_check_spec.rb

@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe Admin::SystemCheck::MissingIndexesCheck do
+  subject(:check) { described_class.new(user) }
+
+  let(:user) { Fabricate(:user) }
+  let(:schema_parser) do
+    instance_double(Admin::Db::SchemaParser, indexes_by_table: index_info)
+  end
+  let(:index_info) do
+    {
+      'users' => [instance_double(Admin::Db::SchemaParser::Index, name: 'index_users_on_profile_id')],
+      'posts' => [instance_double(Admin::Db::SchemaParser::Index, name: 'index_posts_on_user_id')],
+    }
+  end
+  let(:posts_indexes) { [] }
+  let(:users_indexes) { [] }
+
+  before do
+    allow(Admin::Db::SchemaParser).to receive(:new).and_return(schema_parser)
+    allow(ActiveRecord::Base.connection).to receive(:indexes).with('posts').and_return(posts_indexes)
+    allow(ActiveRecord::Base.connection).to receive(:indexes).with('users').and_return(users_indexes)
+  end
+
+  it_behaves_like 'a check available to devops users'
+
+  describe '#pass?' do
+    context 'when indexes are missing' do
+      let(:posts_indexes) do
+        [instance_double(ActiveRecord::ConnectionAdapters::IndexDefinition, name: 'index_posts_on_user_id')]
+      end
+
+      it 'returns false' do
+        expect(check.pass?).to be false
+      end
+    end
+
+    context 'when all expected indexes are present' do
+      let(:posts_indexes) do
+        [instance_double(ActiveRecord::ConnectionAdapters::IndexDefinition, name: 'index_posts_on_user_id')]
+      end
+      let(:users_indexes) do
+        [instance_double(ActiveRecord::ConnectionAdapters::IndexDefinition, name: 'index_users_on_profile_id')]
+      end
+
+      it 'returns true' do
+        expect(check.pass?).to be true
+      end
+    end
+  end
+
+  describe '#message' do
+    subject { check.message }
+
+    it 'sets the class name as the message key' do
+      expect(subject.key).to eq(:missing_indexes_check)
+    end
+
+    it 'sets a list of missing indexes as message value' do
+      expect(subject.value).to eq('index_users_on_profile_id, index_posts_on_user_id')
+    end
+  end
+end