Merge branch 'mk-add-old-attachments-to-uploads-table' into 'master'

Add old files to uploads table

See merge request gitlab-org/gitlab-ce!15270

14 files changed, 1323 insertions, 4 deletions

diff --git a/changelogs/unreleased/mk-add-old-attachments-to-uploads-table.yml b/changelogs/unreleased/mk-add-old-attachments-to-uploads-table.yml
new file mode 100644
index 00000000000..499543ef883
--- /dev/null
+++ b/changelogs/unreleased/mk-add-old-attachments-to-uploads-table.yml
@@ -0,0 +1,5 @@
+---
+title: Add untracked files to uploads table
+merge_request: 15270
+author:
+type: other
diff --git a/db/migrate/20171103000000_set_uploads_path_size_for_mysql.rb b/db/migrate/20171103000000_set_uploads_path_size_for_mysql.rb
new file mode 100644
index 00000000000..1fbe505f804
--- /dev/null
+++ b/db/migrate/20171103000000_set_uploads_path_size_for_mysql.rb
@@ -0,0 +1,25 @@
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class SetUploadsPathSizeForMysql < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  def up
+    # We need at least 297 at the moment. For more detail on that number, see:
+    # https://gitlab.com/gitlab-org/gitlab-ce/issues/40168#what-is-the-expected-correct-behavior
+    #
+    # Rails + PostgreSQL `string` is equivalent to a `text` field, but
+    # Rails + MySQL `string` is `varchar(255)` by default. Also, note that we
+    # have an upper limit because with a unique index, MySQL has a max key
+    # length of 3072 bytes which seems to correspond to `varchar(1024)`.
+    change_column :uploads, :path, :string, limit: 511
+  end
+
+  def down
+    # It was unspecified, which is varchar(255) by default in Rails for MySQL.
+    change_column :uploads, :path, :string
+  end
+end
diff --git a/db/post_migrate/20171103140253_track_untracked_uploads.rb b/db/post_migrate/20171103140253_track_untracked_uploads.rb
new file mode 100644
index 00000000000..548a94d2d38
--- /dev/null
+++ b/db/post_migrate/20171103140253_track_untracked_uploads.rb
@@ -0,0 +1,21 @@
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class TrackUntrackedUploads < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  DOWNTIME = false
+  MIGRATION = 'PrepareUntrackedUploads'
+
+  def up
+    BackgroundMigrationWorker.perform_async(MIGRATION)
+  end
+
+  def down
+    if table_exists?(:untracked_files_for_uploads)
+      drop_table :untracked_files_for_uploads
+    end
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 0984ca6487f..2be1b745342 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -1737,7 +1737,7 @@ ActiveRecord::Schema.define(version: 20171124150326) do
 
   create_table "uploads", force: :cascade do |t|
     t.integer "size", limit: 8, null: false
-    t.string "path", null: false
+    t.string "path", limit: 511, null: false
     t.string "checksum", limit: 64
     t.integer "model_id"
     t.string "model_type"
diff --git a/lib/gitlab/background_migration/populate_untracked_uploads.rb b/lib/gitlab/background_migration/populate_untracked_uploads.rb
new file mode 100644
index 00000000000..81e95e5832d
--- /dev/null
+++ b/lib/gitlab/background_migration/populate_untracked_uploads.rb
@@ -0,0 +1,259 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module BackgroundMigration
+    # This class processes a batch of rows in `untracked_files_for_uploads` by
+    # adding each file to the `uploads` table if it does not exist.
+    class PopulateUntrackedUploads # rubocop:disable Metrics/ClassLength
+      # This class is responsible for producing the attributes necessary to
+      # track an uploaded file in the `uploads` table.
+      class UntrackedFile < ActiveRecord::Base # rubocop:disable Metrics/ClassLength, Metrics/LineLength
+        self.table_name = 'untracked_files_for_uploads'
+
+        # Ends with /:random_hex/:filename
+        FILE_UPLOADER_PATH = %r{/\h+/[^/]+\z}
+        FULL_PATH_CAPTURE = %r{\A(.+)#{FILE_UPLOADER_PATH}}
+
+        # These regex patterns are tested against a relative path, relative to
+        # the upload directory.
+        # For convenience, if there exists a capture group in the pattern, then
+        # it indicates the model_id.
+        PATH_PATTERNS = [
+          {
+            pattern: %r{\A-/system/appearance/logo/(\d+)/},
+            uploader: 'AttachmentUploader',
+            model_type: 'Appearance'
+          },
+          {
+            pattern: %r{\A-/system/appearance/header_logo/(\d+)/},
+            uploader: 'AttachmentUploader',
+            model_type: 'Appearance'
+          },
+          {
+            pattern: %r{\A-/system/note/attachment/(\d+)/},
+            uploader: 'AttachmentUploader',
+            model_type: 'Note'
+          },
+          {
+            pattern: %r{\A-/system/user/avatar/(\d+)/},
+            uploader: 'AvatarUploader',
+            model_type: 'User'
+          },
+          {
+            pattern: %r{\A-/system/group/avatar/(\d+)/},
+            uploader: 'AvatarUploader',
+            model_type: 'Namespace'
+          },
+          {
+            pattern: %r{\A-/system/project/avatar/(\d+)/},
+            uploader: 'AvatarUploader',
+            model_type: 'Project'
+          },
+          {
+            pattern: FILE_UPLOADER_PATH,
+            uploader: 'FileUploader',
+            model_type: 'Project'
+          }
+        ].freeze
+
+        def to_h
+          @upload_hash ||= {
+            path: upload_path,
+            uploader: uploader,
+            model_type: model_type,
+            model_id: model_id,
+            size: file_size,
+            checksum: checksum
+          }
+        end
+
+        def upload_path
+          # UntrackedFile#path is absolute, but Upload#path depends on uploader
+          @upload_path ||=
+            if uploader == 'FileUploader'
+              # Path relative to project directory in uploads
+              matchd = path_relative_to_upload_dir.match(FILE_UPLOADER_PATH)
+              matchd[0].sub(%r{\A/}, '') # remove leading slash
+            else
+              path
+            end
+        end
+
+        def uploader
+          matching_pattern_map[:uploader]
+        end
+
+        def model_type
+          matching_pattern_map[:model_type]
+        end
+
+        def model_id
+          return @model_id if defined?(@model_id)
+
+          pattern = matching_pattern_map[:pattern]
+          matchd = path_relative_to_upload_dir.match(pattern)
+
+          # If something is captured (matchd[1] is not nil), it is a model_id
+          # Only the FileUploader pattern will not match an ID
+          @model_id = matchd[1] ? matchd[1].to_i : file_uploader_model_id
+        end
+
+        def file_size
+          File.size(absolute_path)
+        end
+
+        def checksum
+          Digest::SHA256.file(absolute_path).hexdigest
+        end
+
+        private
+
+        def matching_pattern_map
+          @matching_pattern_map ||= PATH_PATTERNS.find do |path_pattern_map|
+            path_relative_to_upload_dir.match(path_pattern_map[:pattern])
+          end
+
+          unless @matching_pattern_map
+            raise "Unknown upload path pattern \"#{path}\""
+          end
+
+          @matching_pattern_map
+        end
+
+        def file_uploader_model_id
+          matchd = path_relative_to_upload_dir.match(FULL_PATH_CAPTURE)
+          not_found_msg = <<~MSG
+            Could not capture project full_path from a FileUploader path:
+              "#{path_relative_to_upload_dir}"
+          MSG
+          raise not_found_msg unless matchd
+
+          full_path = matchd[1]
+          project = Project.find_by_full_path(full_path)
+          return nil unless project
+
+          project.id
+        end
+
+        # Not including a leading slash
+        def path_relative_to_upload_dir
+          upload_dir = Gitlab::BackgroundMigration::PrepareUntrackedUploads::RELATIVE_UPLOAD_DIR # rubocop:disable Metrics/LineLength
+          base = %r{\A#{Regexp.escape(upload_dir)}/}
+          @path_relative_to_upload_dir ||= path.sub(base, '')
+        end
+
+        def absolute_path
+          File.join(CarrierWave.root, path)
+        end
+      end
+
+      # This class is used to query the `uploads` table.
+      class Upload < ActiveRecord::Base
+        self.table_name = 'uploads'
+      end
+
+      def perform(start_id, end_id)
+        return unless migrate?
+
+        files = UntrackedFile.where(id: start_id..end_id)
+        processed_files = insert_uploads_if_needed(files)
+        processed_files.delete_all
+
+        drop_temp_table_if_finished
+      end
+
+      private
+
+      def migrate?
+        UntrackedFile.table_exists? && Upload.table_exists?
+      end
+
+      def insert_uploads_if_needed(files)
+        filtered_files, error_files = filter_error_files(files)
+        filtered_files = filter_existing_uploads(filtered_files)
+        filtered_files = filter_deleted_models(filtered_files)
+        insert(filtered_files)
+
+        processed_files = files.where.not(id: error_files.map(&:id))
+        processed_files
+      end
+
+      def filter_error_files(files)
+        files.partition do |file|
+          begin
+            file.to_h
+            true
+          rescue => e
+            msg = <<~MSG
+              Error parsing path "#{file.path}":
+                #{e.message}
+                #{e.backtrace.join("\n  ")}
+            MSG
+            Rails.logger.error(msg)
+            false
+          end
+        end
+      end
+
+      def filter_existing_uploads(files)
+        paths = files.map(&:upload_path)
+        existing_paths = Upload.where(path: paths).pluck(:path).to_set
+
+        files.reject do |file|
+          existing_paths.include?(file.upload_path)
+        end
+      end
+
+      # There are files on disk that are not in the uploads table because their
+      # model was deleted, and we don't delete the files on disk.
+      def filter_deleted_models(files)
+        ids = deleted_model_ids(files)
+
+        files.reject do |file|
+          ids[file.model_type].include?(file.model_id)
+        end
+      end
+
+      def deleted_model_ids(files)
+        ids = {
+          'Appearance' => [],
+          'Namespace' => [],
+          'Note' => [],
+          'Project' => [],
+          'User' => []
+        }
+
+        # group model IDs by model type
+        files.each do |file|
+          ids[file.model_type] << file.model_id
+        end
+
+        ids.each do |model_type, model_ids|
+          model_class = Object.const_get(model_type)
+          found_ids = model_class.where(id: model_ids.uniq).pluck(:id)
+          deleted_ids = ids[model_type] - found_ids
+          ids[model_type] = deleted_ids
+        end
+
+        ids
+      end
+
+      def insert(files)
+        rows = files.map do |file|
+          file.to_h.merge(created_at: 'NOW()')
+        end
+
+        Gitlab::Database.bulk_insert('uploads',
+                                     rows,
+                                     disable_quote: :created_at)
+      end
+
+      def drop_temp_table_if_finished
+        if UntrackedFile.all.empty?
+          UntrackedFile.connection.drop_table(:untracked_files_for_uploads,
+                                              if_exists: true)
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/background_migration/prepare_untracked_uploads.rb b/lib/gitlab/background_migration/prepare_untracked_uploads.rb
new file mode 100644
index 00000000000..476c46341ae
--- /dev/null
+++ b/lib/gitlab/background_migration/prepare_untracked_uploads.rb
@@ -0,0 +1,163 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module BackgroundMigration
+    # This class finds all non-hashed uploaded file paths and saves them to a
+    # `untracked_files_for_uploads` table.
+    class PrepareUntrackedUploads # rubocop:disable Metrics/ClassLength
+      # For bulk_queue_background_migration_jobs_by_range
+      include Database::MigrationHelpers
+
+      FIND_BATCH_SIZE = 500
+      RELATIVE_UPLOAD_DIR = "uploads".freeze
+      ABSOLUTE_UPLOAD_DIR = "#{CarrierWave.root}/#{RELATIVE_UPLOAD_DIR}".freeze
+      FOLLOW_UP_MIGRATION = 'PopulateUntrackedUploads'.freeze
+      START_WITH_CARRIERWAVE_ROOT_REGEX = %r{\A#{CarrierWave.root}/}
+      EXCLUDED_HASHED_UPLOADS_PATH = "#{ABSOLUTE_UPLOAD_DIR}/@hashed/*".freeze
+      EXCLUDED_TMP_UPLOADS_PATH = "#{ABSOLUTE_UPLOAD_DIR}/tmp/*".freeze
+
+      # This class is used to iterate over batches of
+      # `untracked_files_for_uploads` rows.
+      class UntrackedFile < ActiveRecord::Base
+        include EachBatch
+
+        self.table_name = 'untracked_files_for_uploads'
+      end
+
+      def perform
+        ensure_temporary_tracking_table_exists
+
+        # Since Postgres < 9.5 does not have ON CONFLICT DO NOTHING, and since
+        # doing inserts-if-not-exists without ON CONFLICT DO NOTHING would be
+        # slow, start with an empty table for Postgres < 9.5.
+        # That way we can do bulk inserts at ~30x the speed of individual
+        # inserts (~20 minutes worth of inserts at GitLab.com scale instead of
+        # ~10 hours).
+        # In all other cases, installations will get both bulk inserts and the
+        # ability for these jobs to retry without having to clear and reinsert.
+        clear_untracked_file_paths unless can_bulk_insert_and_ignore_duplicates?
+
+        store_untracked_file_paths
+
+        schedule_populate_untracked_uploads_jobs
+      end
+
+      private
+
+      def ensure_temporary_tracking_table_exists
+        table_name = :untracked_files_for_uploads
+        unless UntrackedFile.connection.table_exists?(table_name)
+          UntrackedFile.connection.create_table table_name do |t|
+            t.string :path, limit: 600, null: false
+            t.index :path, unique: true
+          end
+        end
+      end
+
+      def clear_untracked_file_paths
+        UntrackedFile.delete_all
+      end
+
+      def store_untracked_file_paths
+        return unless Dir.exist?(ABSOLUTE_UPLOAD_DIR)
+
+        each_file_batch(ABSOLUTE_UPLOAD_DIR, FIND_BATCH_SIZE) do |file_paths|
+          insert_file_paths(file_paths)
+        end
+      end
+
+      def each_file_batch(search_dir, batch_size, &block)
+        cmd = build_find_command(search_dir)
+
+        Open3.popen2(*cmd) do |stdin, stdout, status_thread|
+          yield_paths_in_batches(stdout, batch_size, &block)
+
+          raise "Find command failed" unless status_thread.value.success?
+        end
+      end
+
+      def yield_paths_in_batches(stdout, batch_size, &block)
+        paths = []
+
+        stdout.each_line("\0") do |line|
+          paths << line.chomp("\0").sub(START_WITH_CARRIERWAVE_ROOT_REGEX, '')
+
+          if paths.size >= batch_size
+            yield(paths)
+            paths = []
+          end
+        end
+
+        yield(paths)
+      end
+
+      def build_find_command(search_dir)
+        cmd = %W[find -L #{search_dir}
+                 -type f
+                 ! ( -path #{EXCLUDED_HASHED_UPLOADS_PATH} -prune )
+                 ! ( -path #{EXCLUDED_TMP_UPLOADS_PATH} -prune )
+                 -print0]
+
+        ionice = which_ionice
+        cmd = %W[#{ionice} -c Idle] + cmd if ionice
+
+        log_msg = "PrepareUntrackedUploads find command: \"#{cmd.join(' ')}\""
+        Rails.logger.info log_msg
+
+        cmd
+      end
+
+      def which_ionice
+        Gitlab::Utils.which('ionice')
+      rescue StandardError
+        # In this case, returning false is relatively safe,
+        # even though it isn't very nice
+        false
+      end
+
+      def insert_file_paths(file_paths)
+        sql = insert_sql(file_paths)
+
+        ActiveRecord::Base.connection.execute(sql)
+      end
+
+      def insert_sql(file_paths)
+        if postgresql_pre_9_5?
+          "INSERT INTO #{table_columns_and_values_for_insert(file_paths)};"
+        elsif postgresql?
+          "INSERT INTO #{table_columns_and_values_for_insert(file_paths)}"\
+            " ON CONFLICT DO NOTHING;"
+        else # MySQL
+          "INSERT IGNORE INTO"\
+            " #{table_columns_and_values_for_insert(file_paths)};"
+        end
+      end
+
+      def table_columns_and_values_for_insert(file_paths)
+        values = file_paths.map do |file_path|
+          ActiveRecord::Base.send(:sanitize_sql_array, ['(?)', file_path]) # rubocop:disable GitlabSecurity/PublicSend, Metrics/LineLength
+        end.join(', ')
+
+        "#{UntrackedFile.table_name} (path) VALUES #{values}"
+      end
+
+      def postgresql?
+        @postgresql ||= Gitlab::Database.postgresql?
+      end
+
+      def can_bulk_insert_and_ignore_duplicates?
+        !postgresql_pre_9_5?
+      end
+
+      def postgresql_pre_9_5?
+        @postgresql_pre_9_5 ||= postgresql? &&
+          Gitlab::Database.version.to_f < 9.5
+      end
+
+      def schedule_populate_untracked_uploads_jobs
+        bulk_queue_background_migration_jobs_by_range(
+          UntrackedFile, FOLLOW_UP_MIGRATION)
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/database.rb b/lib/gitlab/database.rb
index 96922e1a62f..e51794fef99 100644
--- a/lib/gitlab/database.rb
+++ b/lib/gitlab/database.rb
@@ -120,15 +120,21 @@ module Gitlab
     #        values.
     # return_ids - When set to true the return value will be an Array of IDs of
     #              the inserted rows, this only works on PostgreSQL.
-    def self.bulk_insert(table, rows, return_ids: false)
+    # disable_quote - A key or an Array of keys to exclude from quoting (You
+    #                 become responsible for protection from SQL injection for
+    #                 these keys!)
+    def self.bulk_insert(table, rows, return_ids: false, disable_quote: [])
       return if rows.empty?
 
       keys = rows.first.keys
       columns = keys.map { |key| connection.quote_column_name(key) }
       return_ids = false if mysql?
 
+      disable_quote = Array(disable_quote).to_set
       tuples = rows.map do |row|
-        row.values_at(*keys).map { |value| connection.quote(value) }
+        keys.map do |k|
+          disable_quote.include?(k) ? row[k] : connection.quote(row[k])
+        end
       end
 
       sql = <<-EOF
diff --git a/lib/gitlab/utils.rb b/lib/gitlab/utils.rb
index abb3d3a02c3..b3baaf036d8 100644
--- a/lib/gitlab/utils.rb
+++ b/lib/gitlab/utils.rb
@@ -46,5 +46,22 @@ module Gitlab
     def random_string
       Random.rand(Float::MAX.to_i).to_s(36)
     end
+
+    # See: http://stackoverflow.com/questions/2108727/which-in-ruby-checking-if-program-exists-in-path-from-ruby
+    # Cross-platform way of finding an executable in the $PATH.
+    #
+    #   which('ruby') #=> /usr/bin/ruby
+    def which(cmd, env = ENV)
+      exts = env['PATHEXT'] ? env['PATHEXT'].split(';') : ['']
+
+      env['PATH'].split(File::PATH_SEPARATOR).each do |path|
+        exts.each do |ext|
+          exe = File.join(path, "#{cmd}#{ext}")
+          return exe if File.executable?(exe) && !File.directory?(exe)
+        end
+      end
+
+      nil
+    end
   end
 end
diff --git a/spec/lib/gitlab/background_migration/populate_untracked_uploads_spec.rb b/spec/lib/gitlab/background_migration/populate_untracked_uploads_spec.rb
new file mode 100644
index 00000000000..b80df6956b0
--- /dev/null
+++ b/spec/lib/gitlab/background_migration/populate_untracked_uploads_spec.rb
@@ -0,0 +1,510 @@
+require 'spec_helper'
+
+describe Gitlab::BackgroundMigration::PopulateUntrackedUploads, :sidekiq do
+  include TrackUntrackedUploadsHelpers
+
+  subject { described_class.new }
+
+  let!(:untracked_files_for_uploads) { described_class::UntrackedFile }
+  let!(:uploads) { described_class::Upload }
+
+  before do
+    DatabaseCleaner.clean
+    drop_temp_table_if_exists
+    ensure_temporary_tracking_table_exists
+    uploads.delete_all
+  end
+
+  after(:all) do
+    drop_temp_table_if_exists
+  end
+
+  context 'with untracked files and tracked files in untracked_files_for_uploads' do
+    let!(:appearance) { create_or_update_appearance(logo: uploaded_file, header_logo: uploaded_file) }
+    let!(:user1) { create(:user, :with_avatar) }
+    let!(:user2) { create(:user, :with_avatar) }
+    let!(:project1) { create(:project, :with_avatar) }
+    let!(:project2) { create(:project, :with_avatar) }
+
+    before do
+      UploadService.new(project1, uploaded_file, FileUploader).execute # Markdown upload
+      UploadService.new(project2, uploaded_file, FileUploader).execute # Markdown upload
+
+      # File records created by PrepareUntrackedUploads
+      untracked_files_for_uploads.create!(path: appearance.uploads.first.path)
+      untracked_files_for_uploads.create!(path: appearance.uploads.last.path)
+      untracked_files_for_uploads.create!(path: user1.uploads.first.path)
+      untracked_files_for_uploads.create!(path: user2.uploads.first.path)
+      untracked_files_for_uploads.create!(path: project1.uploads.first.path)
+      untracked_files_for_uploads.create!(path: project2.uploads.first.path)
+      untracked_files_for_uploads.create!(path: "#{Gitlab::BackgroundMigration::PrepareUntrackedUploads::RELATIVE_UPLOAD_DIR}/#{project1.full_path}/#{project1.uploads.last.path}")
+      untracked_files_for_uploads.create!(path: "#{Gitlab::BackgroundMigration::PrepareUntrackedUploads::RELATIVE_UPLOAD_DIR}/#{project2.full_path}/#{project2.uploads.last.path}")
+
+      # Untrack 4 files
+      user2.uploads.delete_all
+      project2.uploads.delete_all # 2 files: avatar and a Markdown upload
+      appearance.uploads.where("path like '%header_logo%'").delete_all
+    end
+
+    it 'adds untracked files to the uploads table' do
+      expect do
+        subject.perform(1, untracked_files_for_uploads.last.id)
+      end.to change { uploads.count }.from(4).to(8)
+
+      expect(user2.uploads.count).to eq(1)
+      expect(project2.uploads.count).to eq(2)
+      expect(appearance.uploads.count).to eq(2)
+    end
+
+    it 'deletes rows after processing them' do
+      expect(subject).to receive(:drop_temp_table_if_finished) # Don't drop the table so we can look at it
+
+      expect do
+        subject.perform(1, untracked_files_for_uploads.last.id)
+      end.to change { untracked_files_for_uploads.count }.from(8).to(0)
+    end
+
+    it 'does not create duplicate uploads of already tracked files' do
+      subject.perform(1, untracked_files_for_uploads.last.id)
+
+      expect(user1.uploads.count).to eq(1)
+      expect(project1.uploads.count).to eq(2)
+      expect(appearance.uploads.count).to eq(2)
+    end
+
+    it 'uses the start and end batch ids [only 1st half]' do
+      ids = untracked_files_for_uploads.all.order(:id).pluck(:id)
+      start_id = ids[0]
+      end_id = ids[3]
+
+      expect do
+        subject.perform(start_id, end_id)
+      end.to change { uploads.count }.from(4).to(6)
+
+      expect(user1.uploads.count).to eq(1)
+      expect(user2.uploads.count).to eq(1)
+      expect(appearance.uploads.count).to eq(2)
+      expect(project1.uploads.count).to eq(2)
+      expect(project2.uploads.count).to eq(0)
+
+      # Only 4 have been either confirmed or added to uploads
+      expect(untracked_files_for_uploads.count).to eq(4)
+    end
+
+    it 'uses the start and end batch ids [only 2nd half]' do
+      ids = untracked_files_for_uploads.all.order(:id).pluck(:id)
+      start_id = ids[4]
+      end_id = ids[7]
+
+      expect do
+        subject.perform(start_id, end_id)
+      end.to change { uploads.count }.from(4).to(6)
+
+      expect(user1.uploads.count).to eq(1)
+      expect(user2.uploads.count).to eq(0)
+      expect(appearance.uploads.count).to eq(1)
+      expect(project1.uploads.count).to eq(2)
+      expect(project2.uploads.count).to eq(2)
+
+      # Only 4 have been either confirmed or added to uploads
+      expect(untracked_files_for_uploads.count).to eq(4)
+    end
+
+    it 'does not drop the temporary tracking table after processing the batch, if there are still untracked rows' do
+      subject.perform(1, untracked_files_for_uploads.last.id - 1)
+
+      expect(ActiveRecord::Base.connection.table_exists?(:untracked_files_for_uploads)).to be_truthy
+    end
+
+    it 'drops the temporary tracking table after processing the batch, if there are no untracked rows left' do
+      subject.perform(1, untracked_files_for_uploads.last.id)
+
+      expect(ActiveRecord::Base.connection.table_exists?(:untracked_files_for_uploads)).to be_falsey
+    end
+
+    it 'does not block a whole batch because of one bad path' do
+      untracked_files_for_uploads.create!(path: "#{Gitlab::BackgroundMigration::PrepareUntrackedUploads::RELATIVE_UPLOAD_DIR}/#{project2.full_path}/._7d37bf4c747916390e596744117d5d1a")
+      expect(untracked_files_for_uploads.count).to eq(9)
+      expect(uploads.count).to eq(4)
+
+      subject.perform(1, untracked_files_for_uploads.last.id)
+
+      expect(untracked_files_for_uploads.count).to eq(1)
+      expect(uploads.count).to eq(8)
+    end
+
+    it 'an unparseable path is shown in error output' do
+      bad_path = "#{Gitlab::BackgroundMigration::PrepareUntrackedUploads::RELATIVE_UPLOAD_DIR}/#{project2.full_path}/._7d37bf4c747916390e596744117d5d1a"
+      untracked_files_for_uploads.create!(path: bad_path)
+
+      expect(Rails.logger).to receive(:error).with(/Error parsing path "#{bad_path}":/)
+
+      subject.perform(1, untracked_files_for_uploads.last.id)
+    end
+  end
+
+  context 'with no untracked files' do
+    it 'does not add to the uploads table (and does not raise error)' do
+      expect do
+        subject.perform(1, 1000)
+      end.not_to change { uploads.count }.from(0)
+    end
+  end
+
+  describe 'upload outcomes for each path pattern' do
+    shared_examples_for 'non_markdown_file' do
+      let!(:expected_upload_attrs) { model.uploads.first.attributes.slice('path', 'uploader', 'size', 'checksum') }
+      let!(:untracked_file) { untracked_files_for_uploads.create!(path: expected_upload_attrs['path']) }
+
+      before do
+        model.uploads.delete_all
+      end
+
+      it 'creates an Upload record' do
+        expect do
+          subject.perform(1, untracked_files_for_uploads.last.id)
+        end.to change { model.reload.uploads.count }.from(0).to(1)
+
+        expect(model.uploads.first.attributes).to include(expected_upload_attrs)
+      end
+    end
+
+    context 'for an appearance logo file path' do
+      let(:model) { create_or_update_appearance(logo: uploaded_file) }
+
+      it_behaves_like 'non_markdown_file'
+    end
+
+    context 'for an appearance header_logo file path' do
+      let(:model) { create_or_update_appearance(header_logo: uploaded_file) }
+
+      it_behaves_like 'non_markdown_file'
+    end
+
+    context 'for a pre-Markdown Note attachment file path' do
+      class Note < ActiveRecord::Base
+        has_many :uploads, as: :model, dependent: :destroy
+      end
+
+      let(:model) { create(:note, :with_attachment) }
+
+      it_behaves_like 'non_markdown_file'
+    end
+
+    context 'for a user avatar file path' do
+      let(:model) { create(:user, :with_avatar) }
+
+      it_behaves_like 'non_markdown_file'
+    end
+
+    context 'for a group avatar file path' do
+      let(:model) { create(:group, :with_avatar) }
+
+      it_behaves_like 'non_markdown_file'
+    end
+
+    context 'for a project avatar file path' do
+      let(:model) { create(:project, :with_avatar) }
+
+      it_behaves_like 'non_markdown_file'
+    end
+
+    context 'for a project Markdown attachment (notes, issues, MR descriptions) file path' do
+      let(:model) { create(:project) }
+
+      before do
+        # Upload the file
+        UploadService.new(model, uploaded_file, FileUploader).execute
+
+        # Create the untracked_files_for_uploads record
+        untracked_files_for_uploads.create!(path: "#{Gitlab::BackgroundMigration::PrepareUntrackedUploads::RELATIVE_UPLOAD_DIR}/#{model.full_path}/#{model.uploads.first.path}")
+
+        # Save the expected upload attributes
+        @expected_upload_attrs = model.reload.uploads.first.attributes.slice('path', 'uploader', 'size', 'checksum')
+
+        # Untrack the file
+        model.reload.uploads.delete_all
+      end
+
+      it 'creates an Upload record' do
+        expect do
+          subject.perform(1, untracked_files_for_uploads.last.id)
+        end.to change { model.reload.uploads.count }.from(0).to(1)
+
+        expect(model.uploads.first.attributes).to include(@expected_upload_attrs)
+      end
+    end
+  end
+end
+
+describe Gitlab::BackgroundMigration::PopulateUntrackedUploads::UntrackedFile do
+  include TrackUntrackedUploadsHelpers
+
+  let(:upload_class) { Gitlab::BackgroundMigration::PopulateUntrackedUploads::Upload }
+
+  before(:all) do
+    ensure_temporary_tracking_table_exists
+  end
+
+  after(:all) do
+    drop_temp_table_if_exists
+  end
+
+  describe '#upload_path' do
+    def assert_upload_path(file_path, expected_upload_path)
+      untracked_file = create_untracked_file(file_path)
+
+      expect(untracked_file.upload_path).to eq(expected_upload_path)
+    end
+
+    context 'for an appearance logo file path' do
+      it 'returns the file path relative to the CarrierWave root' do
+        assert_upload_path('/-/system/appearance/logo/1/some_logo.jpg', 'uploads/-/system/appearance/logo/1/some_logo.jpg')
+      end
+    end
+
+    context 'for an appearance header_logo file path' do
+      it 'returns the file path relative to the CarrierWave root' do
+        assert_upload_path('/-/system/appearance/header_logo/1/some_logo.jpg', 'uploads/-/system/appearance/header_logo/1/some_logo.jpg')
+      end
+    end
+
+    context 'for a pre-Markdown Note attachment file path' do
+      it 'returns the file path relative to the CarrierWave root' do
+        assert_upload_path('/-/system/note/attachment/1234/some_attachment.pdf', 'uploads/-/system/note/attachment/1234/some_attachment.pdf')
+      end
+    end
+
+    context 'for a user avatar file path' do
+      it 'returns the file path relative to the CarrierWave root' do
+        assert_upload_path('/-/system/user/avatar/1234/avatar.jpg', 'uploads/-/system/user/avatar/1234/avatar.jpg')
+      end
+    end
+
+    context 'for a group avatar file path' do
+      it 'returns the file path relative to the CarrierWave root' do
+        assert_upload_path('/-/system/group/avatar/1234/avatar.jpg', 'uploads/-/system/group/avatar/1234/avatar.jpg')
+      end
+    end
+
+    context 'for a project avatar file path' do
+      it 'returns the file path relative to the CarrierWave root' do
+        assert_upload_path('/-/system/project/avatar/1234/avatar.jpg', 'uploads/-/system/project/avatar/1234/avatar.jpg')
+      end
+    end
+
+    context 'for a project Markdown attachment (notes, issues, MR descriptions) file path' do
+      it 'returns the file path relative to the project directory in uploads' do
+        project = create(:project)
+        random_hex = SecureRandom.hex
+
+        assert_upload_path("/#{project.full_path}/#{random_hex}/Some file.jpg", "#{random_hex}/Some file.jpg")
+      end
+    end
+  end
+
+  describe '#uploader' do
+    def assert_uploader(file_path, expected_uploader)
+      untracked_file = create_untracked_file(file_path)
+
+      expect(untracked_file.uploader).to eq(expected_uploader)
+    end
+
+    context 'for an appearance logo file path' do
+      it 'returns AttachmentUploader as a string' do
+        assert_uploader('/-/system/appearance/logo/1/some_logo.jpg', 'AttachmentUploader')
+      end
+    end
+
+    context 'for an appearance header_logo file path' do
+      it 'returns AttachmentUploader as a string' do
+        assert_uploader('/-/system/appearance/header_logo/1/some_logo.jpg', 'AttachmentUploader')
+      end
+    end
+
+    context 'for a pre-Markdown Note attachment file path' do
+      it 'returns AttachmentUploader as a string' do
+        assert_uploader('/-/system/note/attachment/1234/some_attachment.pdf', 'AttachmentUploader')
+      end
+    end
+
+    context 'for a user avatar file path' do
+      it 'returns AvatarUploader as a string' do
+        assert_uploader('/-/system/user/avatar/1234/avatar.jpg', 'AvatarUploader')
+      end
+    end
+
+    context 'for a group avatar file path' do
+      it 'returns AvatarUploader as a string' do
+        assert_uploader('/-/system/group/avatar/1234/avatar.jpg', 'AvatarUploader')
+      end
+    end
+
+    context 'for a project avatar file path' do
+      it 'returns AvatarUploader as a string' do
+        assert_uploader('/-/system/project/avatar/1234/avatar.jpg', 'AvatarUploader')
+      end
+    end
+
+    context 'for a project Markdown attachment (notes, issues, MR descriptions) file path' do
+      it 'returns FileUploader as a string' do
+        project = create(:project)
+
+        assert_uploader("/#{project.full_path}/#{SecureRandom.hex}/Some file.jpg", 'FileUploader')
+      end
+    end
+  end
+
+  describe '#model_type' do
+    def assert_model_type(file_path, expected_model_type)
+      untracked_file = create_untracked_file(file_path)
+
+      expect(untracked_file.model_type).to eq(expected_model_type)
+    end
+
+    context 'for an appearance logo file path' do
+      it 'returns Appearance as a string' do
+        assert_model_type('/-/system/appearance/logo/1/some_logo.jpg', 'Appearance')
+      end
+    end
+
+    context 'for an appearance header_logo file path' do
+      it 'returns Appearance as a string' do
+        assert_model_type('/-/system/appearance/header_logo/1/some_logo.jpg', 'Appearance')
+      end
+    end
+
+    context 'for a pre-Markdown Note attachment file path' do
+      it 'returns Note as a string' do
+        assert_model_type('/-/system/note/attachment/1234/some_attachment.pdf', 'Note')
+      end
+    end
+
+    context 'for a user avatar file path' do
+      it 'returns User as a string' do
+        assert_model_type('/-/system/user/avatar/1234/avatar.jpg', 'User')
+      end
+    end
+
+    context 'for a group avatar file path' do
+      it 'returns Namespace as a string' do
+        assert_model_type('/-/system/group/avatar/1234/avatar.jpg', 'Namespace')
+      end
+    end
+
+    context 'for a project avatar file path' do
+      it 'returns Project as a string' do
+        assert_model_type('/-/system/project/avatar/1234/avatar.jpg', 'Project')
+      end
+    end
+
+    context 'for a project Markdown attachment (notes, issues, MR descriptions) file path' do
+      it 'returns Project as a string' do
+        project = create(:project)
+
+        assert_model_type("/#{project.full_path}/#{SecureRandom.hex}/Some file.jpg", 'Project')
+      end
+    end
+  end
+
+  describe '#model_id' do
+    def assert_model_id(file_path, expected_model_id)
+      untracked_file = create_untracked_file(file_path)
+
+      expect(untracked_file.model_id).to eq(expected_model_id)
+    end
+
+    context 'for an appearance logo file path' do
+      it 'returns the ID as a string' do
+        assert_model_id('/-/system/appearance/logo/1/some_logo.jpg', 1)
+      end
+    end
+
+    context 'for an appearance header_logo file path' do
+      it 'returns the ID as a string' do
+        assert_model_id('/-/system/appearance/header_logo/1/some_logo.jpg', 1)
+      end
+    end
+
+    context 'for a pre-Markdown Note attachment file path' do
+      it 'returns the ID as a string' do
+        assert_model_id('/-/system/note/attachment/1234/some_attachment.pdf', 1234)
+      end
+    end
+
+    context 'for a user avatar file path' do
+      it 'returns the ID as a string' do
+        assert_model_id('/-/system/user/avatar/1234/avatar.jpg', 1234)
+      end
+    end
+
+    context 'for a group avatar file path' do
+      it 'returns the ID as a string' do
+        assert_model_id('/-/system/group/avatar/1234/avatar.jpg', 1234)
+      end
+    end
+
+    context 'for a project avatar file path' do
+      it 'returns the ID as a string' do
+        assert_model_id('/-/system/project/avatar/1234/avatar.jpg', 1234)
+      end
+    end
+
+    context 'for a project Markdown attachment (notes, issues, MR descriptions) file path' do
+      it 'returns the ID as a string' do
+        project = create(:project)
+
+        assert_model_id("/#{project.full_path}/#{SecureRandom.hex}/Some file.jpg", project.id)
+      end
+    end
+  end
+
+  describe '#file_size' do
+    context 'for an appearance logo file path' do
+      let(:appearance) { create_or_update_appearance(logo: uploaded_file) }
+      let(:untracked_file) { described_class.create!(path: appearance.uploads.first.path) }
+
+      it 'returns the file size' do
+        expect(untracked_file.file_size).to eq(35255)
+      end
+
+      it 'returns the same thing that CarrierWave would return' do
+        expect(untracked_file.file_size).to eq(appearance.logo.size)
+      end
+    end
+
+    context 'for a project avatar file path' do
+      let(:project) { create(:project, avatar: uploaded_file) }
+      let(:untracked_file) { described_class.create!(path: project.uploads.first.path) }
+
+      it 'returns the file size' do
+        expect(untracked_file.file_size).to eq(35255)
+      end
+
+      it 'returns the same thing that CarrierWave would return' do
+        expect(untracked_file.file_size).to eq(project.avatar.size)
+      end
+    end
+
+    context 'for a project Markdown attachment (notes, issues, MR descriptions) file path' do
+      let(:project) { create(:project) }
+      let(:untracked_file) { create_untracked_file("/#{project.full_path}/#{project.uploads.first.path}") }
+
+      before do
+        UploadService.new(project, uploaded_file, FileUploader).execute
+      end
+
+      it 'returns the file size' do
+        expect(untracked_file.file_size).to eq(35255)
+      end
+
+      it 'returns the same thing that CarrierWave would return' do
+        expect(untracked_file.file_size).to eq(project.uploads.first.size)
+      end
+    end
+  end
+
+  def create_untracked_file(path_relative_to_upload_dir)
+    described_class.create!(path: "#{Gitlab::BackgroundMigration::PrepareUntrackedUploads::RELATIVE_UPLOAD_DIR}#{path_relative_to_upload_dir}")
+  end
+end
diff --git a/spec/lib/gitlab/background_migration/prepare_untracked_uploads_spec.rb b/spec/lib/gitlab/background_migration/prepare_untracked_uploads_spec.rb
new file mode 100644
index 00000000000..cd3f1a45270
--- /dev/null
+++ b/spec/lib/gitlab/background_migration/prepare_untracked_uploads_spec.rb
@@ -0,0 +1,242 @@
+require 'spec_helper'
+
+describe Gitlab::BackgroundMigration::PrepareUntrackedUploads, :sidekiq do
+  include TrackUntrackedUploadsHelpers
+
+  let!(:untracked_files_for_uploads) { described_class::UntrackedFile }
+
+  matcher :be_scheduled_migration do |*expected|
+    match do |migration|
+      BackgroundMigrationWorker.jobs.any? do |job|
+        job['args'] == [migration, expected]
+      end
+    end
+
+    failure_message do |migration|
+      "Migration `#{migration}` with args `#{expected.inspect}` not scheduled!"
+    end
+  end
+
+  before do
+    DatabaseCleaner.clean
+
+    drop_temp_table_if_exists
+  end
+
+  after do
+    drop_temp_table_if_exists
+  end
+
+  around do |example|
+    # Especially important so the follow-up migration does not get run
+    Sidekiq::Testing.fake! do
+      example.run
+    end
+  end
+
+  it 'ensures the untracked_files_for_uploads table exists' do
+    expect do
+      described_class.new.perform
+    end.to change { ActiveRecord::Base.connection.table_exists?(:untracked_files_for_uploads) }.from(false).to(true)
+  end
+
+  it 'has a path field long enough for really long paths' do
+    described_class.new.perform
+
+    component = 'a' * 255
+
+    long_path = [
+      'uploads',
+      component, # project.full_path
+      component  # filename
+    ].flatten.join('/')
+
+    record = untracked_files_for_uploads.create!(path: long_path)
+    expect(record.reload.path.size).to eq(519)
+  end
+
+  context "test bulk insert with ON CONFLICT DO NOTHING or IGNORE" do
+    around do |example|
+      # If this is CI, we use Postgres 9.2 so this whole context should be
+      # skipped since we're unable to use ON CONFLICT DO NOTHING or IGNORE.
+      if described_class.new.send(:can_bulk_insert_and_ignore_duplicates?)
+        example.run
+      end
+    end
+
+    context 'when files were uploaded before and after hashed storage was enabled' do
+      let!(:appearance) { create_or_update_appearance(logo: uploaded_file, header_logo: uploaded_file) }
+      let!(:user) { create(:user, :with_avatar) }
+      let!(:project1) { create(:project, :with_avatar) }
+      let(:project2) { create(:project) } # instantiate after enabling hashed_storage
+
+      before do
+        # Markdown upload before enabling hashed_storage
+        UploadService.new(project1, uploaded_file, FileUploader).execute
+
+        stub_application_setting(hashed_storage_enabled: true)
+
+        # Markdown upload after enabling hashed_storage
+        UploadService.new(project2, uploaded_file, FileUploader).execute
+      end
+
+      it 'adds unhashed files to the untracked_files_for_uploads table' do
+        described_class.new.perform
+
+        expect(untracked_files_for_uploads.count).to eq(5)
+      end
+
+      it 'adds files with paths relative to CarrierWave.root' do
+        described_class.new.perform
+        untracked_files_for_uploads.all.each do |file|
+          expect(file.path.start_with?('uploads/')).to be_truthy
+        end
+      end
+
+      it 'does not add hashed files to the untracked_files_for_uploads table' do
+        described_class.new.perform
+
+        hashed_file_path = project2.uploads.where(uploader: 'FileUploader').first.path
+        expect(untracked_files_for_uploads.where("path like '%#{hashed_file_path}%'").exists?).to be_falsey
+      end
+
+      it 'correctly schedules the follow-up background migration jobs' do
+        described_class.new.perform
+
+        expect(described_class::FOLLOW_UP_MIGRATION).to be_scheduled_migration(1, 5)
+        expect(BackgroundMigrationWorker.jobs.size).to eq(1)
+      end
+
+      # E.g. from a previous failed run of this background migration
+      context 'when there is existing data in untracked_files_for_uploads' do
+        before do
+          described_class.new.perform
+        end
+
+        it 'does not error or produce duplicates of existing data' do
+          expect do
+            described_class.new.perform
+          end.not_to change { untracked_files_for_uploads.count }.from(5)
+        end
+      end
+
+      # E.g. The installation is in use at the time of migration, and someone has
+      # just uploaded a file
+      context 'when there are files in /uploads/tmp' do
+        let(:tmp_file) { Rails.root.join(described_class::ABSOLUTE_UPLOAD_DIR, 'tmp', 'some_file.jpg') }
+
+        before do
+          FileUtils.touch(tmp_file)
+        end
+
+        after do
+          FileUtils.rm(tmp_file)
+        end
+
+        it 'does not add files from /uploads/tmp' do
+          described_class.new.perform
+
+          expect(untracked_files_for_uploads.count).to eq(5)
+        end
+      end
+    end
+  end
+
+  context 'test bulk insert without ON CONFLICT DO NOTHING or IGNORE' do
+    before do
+      # If this is CI, we use Postgres 9.2 so this stub has no effect.
+      #
+      # If this is being run on Postgres 9.5+ or MySQL, then this stub allows us
+      # to test the bulk insert functionality without ON CONFLICT DO NOTHING or
+      # IGNORE.
+      allow_any_instance_of(described_class).to receive(:postgresql_pre_9_5?).and_return(true)
+    end
+
+    context 'when files were uploaded before and after hashed storage was enabled' do
+      let!(:appearance) { create_or_update_appearance(logo: uploaded_file, header_logo: uploaded_file) }
+      let!(:user) { create(:user, :with_avatar) }
+      let!(:project1) { create(:project, :with_avatar) }
+      let(:project2) { create(:project) } # instantiate after enabling hashed_storage
+
+      before do
+        # Markdown upload before enabling hashed_storage
+        UploadService.new(project1, uploaded_file, FileUploader).execute
+
+        stub_application_setting(hashed_storage_enabled: true)
+
+        # Markdown upload after enabling hashed_storage
+        UploadService.new(project2, uploaded_file, FileUploader).execute
+      end
+
+      it 'adds unhashed files to the untracked_files_for_uploads table' do
+        described_class.new.perform
+
+        expect(untracked_files_for_uploads.count).to eq(5)
+      end
+
+      it 'adds files with paths relative to CarrierWave.root' do
+        described_class.new.perform
+        untracked_files_for_uploads.all.each do |file|
+          expect(file.path.start_with?('uploads/')).to be_truthy
+        end
+      end
+
+      it 'does not add hashed files to the untracked_files_for_uploads table' do
+        described_class.new.perform
+
+        hashed_file_path = project2.uploads.where(uploader: 'FileUploader').first.path
+        expect(untracked_files_for_uploads.where("path like '%#{hashed_file_path}%'").exists?).to be_falsey
+      end
+
+      it 'correctly schedules the follow-up background migration jobs' do
+        described_class.new.perform
+
+        expect(described_class::FOLLOW_UP_MIGRATION).to be_scheduled_migration(1, 5)
+        expect(BackgroundMigrationWorker.jobs.size).to eq(1)
+      end
+
+      # E.g. from a previous failed run of this background migration
+      context 'when there is existing data in untracked_files_for_uploads' do
+        before do
+          described_class.new.perform
+        end
+
+        it 'does not error or produce duplicates of existing data' do
+          expect do
+            described_class.new.perform
+          end.not_to change { untracked_files_for_uploads.count }.from(5)
+        end
+      end
+
+      # E.g. The installation is in use at the time of migration, and someone has
+      # just uploaded a file
+      context 'when there are files in /uploads/tmp' do
+        let(:tmp_file) { Rails.root.join(described_class::ABSOLUTE_UPLOAD_DIR, 'tmp', 'some_file.jpg') }
+
+        before do
+          FileUtils.touch(tmp_file)
+        end
+
+        after do
+          FileUtils.rm(tmp_file)
+        end
+
+        it 'does not add files from /uploads/tmp' do
+          described_class.new.perform
+
+          expect(untracked_files_for_uploads.count).to eq(5)
+        end
+      end
+    end
+  end
+
+  # Very new or lightly-used installations that are running this migration
+  # may not have an upload directory because they have no uploads.
+  context 'when no files were ever uploaded' do
+    it 'does not add to the untracked_files_for_uploads table (and does not raise error)' do
+      described_class.new.perform
+
+      expect(untracked_files_for_uploads.count).to eq(0)
+    end
+  end
+end
diff --git a/spec/lib/gitlab/database_spec.rb b/spec/lib/gitlab/database_spec.rb
index a5657b81952..b2f13fae73f 100644
--- a/spec/lib/gitlab/database_spec.rb
+++ b/spec/lib/gitlab/database_spec.rb
@@ -221,6 +221,22 @@ describe Gitlab::Database do
       described_class.bulk_insert('test', rows)
     end
 
+    it 'does not quote values of a column in the disable_quote option' do
+      [1, 2, 4, 5].each do |i|
+        expect(connection).to receive(:quote).with(i)
+      end
+
+      described_class.bulk_insert('test', rows, disable_quote: :c)
+    end
+
+    it 'does not quote values of columns in the disable_quote option' do
+      [2, 5].each do |i|
+        expect(connection).to receive(:quote).with(i)
+      end
+
+      described_class.bulk_insert('test', rows, disable_quote: [:a, :c])
+    end
+
     it 'handles non-UTF-8 data' do
       expect { described_class.bulk_insert('test', [{ a: "\255" }]) }.not_to raise_error
     end
diff --git a/spec/lib/gitlab/utils_spec.rb b/spec/lib/gitlab/utils_spec.rb
index 3137a72fdc4..e872a5290c5 100644
--- a/spec/lib/gitlab/utils_spec.rb
+++ b/spec/lib/gitlab/utils_spec.rb
@@ -1,7 +1,7 @@
 require 'spec_helper'
 
 describe Gitlab::Utils do
-  delegate :to_boolean, :boolean_to_yes_no, :slugify, :random_string, to: :described_class
+  delegate :to_boolean, :boolean_to_yes_no, :slugify, :random_string, :which, to: :described_class
 
   describe '.slugify' do
     {
@@ -59,4 +59,12 @@ describe Gitlab::Utils do
       expect(random_string).to be_kind_of(String)
     end
   end
+
+  describe '.which' do
+    it 'finds the full path to an executable binary' do
+      expect(File).to receive(:executable?).with('/bin/sh').and_return(true)
+
+      expect(which('sh', 'PATH' => '/bin')).to eq('/bin/sh')
+    end
+  end
 end
diff --git a/spec/migrations/track_untracked_uploads_spec.rb b/spec/migrations/track_untracked_uploads_spec.rb
new file mode 100644
index 00000000000..7fe7a140e2f
--- /dev/null
+++ b/spec/migrations/track_untracked_uploads_spec.rb
@@ -0,0 +1,27 @@
+require 'spec_helper'
+require Rails.root.join('db', 'post_migrate', '20171103140253_track_untracked_uploads')
+
+describe TrackUntrackedUploads, :migration, :sidekiq do
+  include TrackUntrackedUploadsHelpers
+
+  matcher :be_scheduled_migration do
+    match do |migration|
+      BackgroundMigrationWorker.jobs.any? do |job|
+        job['args'] == [migration]
+      end
+    end
+
+    failure_message do |migration|
+      "Migration `#{migration}` with args `#{expected.inspect}` not scheduled!"
+    end
+  end
+
+  it 'correctly schedules the follow-up background migration' do
+    Sidekiq::Testing.fake! do
+      migrate!
+
+      expect(described_class::MIGRATION).to be_scheduled_migration
+      expect(BackgroundMigrationWorker.jobs.size).to eq(1)
+    end
+  end
+end
diff --git a/spec/support/track_untracked_uploads_helpers.rb b/spec/support/track_untracked_uploads_helpers.rb
new file mode 100644
index 00000000000..d05eda08201
--- /dev/null
+++ b/spec/support/track_untracked_uploads_helpers.rb
@@ -0,0 +1,20 @@
+module TrackUntrackedUploadsHelpers
+  def uploaded_file
+    fixture_path = Rails.root.join('spec', 'fixtures', 'rails_sample.jpg')
+    fixture_file_upload(fixture_path)
+  end
+
+  def ensure_temporary_tracking_table_exists
+    Gitlab::BackgroundMigration::PrepareUntrackedUploads.new.send(:ensure_temporary_tracking_table_exists)
+  end
+
+  def drop_temp_table_if_exists
+    ActiveRecord::Base.connection.drop_table(:untracked_files_for_uploads) if ActiveRecord::Base.connection.table_exists?(:untracked_files_for_uploads)
+  end
+
+  def create_or_update_appearance(attrs)
+    a = Appearance.first_or_initialize(title: 'foo', description: 'bar')
+    a.update!(attrs)
+    a
+  end
+end