Rename the Repository table to PoolRepository

To separate the different kinds of repositories we have at GitLab this
table will be renamed to pool_repositories. A project can, for now at
least, be member of none, or one of these. The table will get additional
columns in a later merge request where more logic is implemented for the
model.

Further included is a small refactor of logic around hashing ids for the
disk_path, mainly to ensure a previous implementation is reusable.

The disk_path for the pool_repositories table no longer has a NOT NULL
constraint, but given the hashing of the ID requires the DB to assign
the record an ID, an after_create hook is used to update the value.

A related MR is:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/23143, adding
tables for 'normal' repositories and wiki_repositories.

app/models/pool_repository.rb

 # frozen_string_literal: true
 
 class PoolRepository < ActiveRecord::Base
-  POOL_PREFIX = '@pools'
-
   belongs_to :shard
   validates :shard, presence: true
 
-  # For now, only pool repositories are tracked in the database. However, we may
-  # want to add other repository types in the future
-  self.table_name = 'repositories'
+  has_many :member_projects, class_name: 'Project'
 
-  has_many :pool_member_projects, class_name: 'Project', foreign_key: :pool_repository_id
+  after_create :correct_disk_path
 
   def shard_name
     shard&.name
@@ -19,4 +15,15 @@ class PoolRepository < ActiveRecord::Base
   def shard_name=(name)
     self.shard = Shard.by_name(name)
   end
+
+  private
+
+  def correct_disk_path
+    update(disk_path: storage.disk_path)
+  end
+
+  def storage
+    Storage::HashedProject
+      .new(self, prefix: Storage::HashedProject::POOL_PATH_PREFIX)
+  end
 end

app/models/storage/hashed_project.rb

@@ -5,17 +5,19 @@ module Storage
     attr_accessor :project
     delegate :gitlab_shell, :repository_storage, to: :project
 
-    ROOT_PATH_PREFIX = '@hashed'.freeze
+    REPOSITORY_PATH_PREFIX = '@hashed'
+    POOL_PATH_PREFIX = '@pools'
 
-    def initialize(project)
+    def initialize(project, prefix: REPOSITORY_PATH_PREFIX)
       @project = project
+      @prefix = prefix
     end
 
     # Base directory
     #
     # @return [String] directory where repository is stored
     def base_dir
-      "#{ROOT_PATH_PREFIX}/#{disk_hash[0..1]}/#{disk_hash[2..3]}" if disk_hash
+      "#{@prefix}/#{disk_hash[0..1]}/#{disk_hash[2..3]}" if disk_hash
     end
 
     # Disk path is used to build repository and project's wiki path on disk

db/migrate/20181120082911_rename_repositories_pool_repositories.rb

+class RenameRepositoriesPoolRepositories < ActiveRecord::Migration[5.0]
+  include Gitlab::Database::MigrationHelpers
+
+  # This change doesn't require downtime as the table is not in use, so we're
+  # free to change an empty table
+  DOWNTIME = false
+
+  def change
+    rename_table :repositories, :pool_repositories
+  end
+end

db/migrate/20181123135036_drop_not_null_constraint_pool_repository_disk_path.rb

+# frozen_string_literal: true
+
+class DropNotNullConstraintPoolRepositoryDiskPath < ActiveRecord::Migration[5.0]
+  DOWNTIME = false
+
+  def change
+    change_column_null :pool_repositories, :disk_path, true
+  end
+end

db/schema.rb

@@ -1501,6 +1501,13 @@ ActiveRecord::Schema.define(version: 20181126153547) do
     t.index ["user_id"], name: "index_personal_access_tokens_on_user_id", using: :btree
   end
 
+  create_table "pool_repositories", id: :bigserial, force: :cascade do |t|
+    t.integer "shard_id", null: false
+    t.string "disk_path"
+    t.index ["disk_path"], name: "index_pool_repositories_on_disk_path", unique: true, using: :btree
+    t.index ["shard_id"], name: "index_pool_repositories_on_shard_id", using: :btree
+  end
+
   create_table "programming_languages", force: :cascade do |t|
     t.string "name", null: false
     t.string "color", null: false
@@ -1798,13 +1805,6 @@ ActiveRecord::Schema.define(version: 20181126153547) do
     t.index ["project_id"], name: "index_remote_mirrors_on_project_id", using: :btree
   end
 
-  create_table "repositories", id: :bigserial, force: :cascade do |t|
-    t.integer "shard_id", null: false
-    t.string "disk_path", null: false
-    t.index ["disk_path"], name: "index_repositories_on_disk_path", unique: true, using: :btree
-    t.index ["shard_id"], name: "index_repositories_on_shard_id", using: :btree
-  end
-
   create_table "repository_languages", id: false, force: :cascade do |t|
     t.integer "project_id", null: false
     t.integer "programming_language_id", null: false
@@ -2377,6 +2377,7 @@ ActiveRecord::Schema.define(version: 20181126153547) do
   add_foreign_key "oauth_openid_requests", "oauth_access_grants", column: "access_grant_id", name: "fk_oauth_openid_requests_oauth_access_grants_access_grant_id"
   add_foreign_key "pages_domains", "projects", name: "fk_ea2f6dfc6f", on_delete: :cascade
   add_foreign_key "personal_access_tokens", "users"
+  add_foreign_key "pool_repositories", "shards", on_delete: :restrict
   add_foreign_key "project_authorizations", "projects", on_delete: :cascade
   add_foreign_key "project_authorizations", "users", on_delete: :cascade
   add_foreign_key "project_auto_devops", "projects", on_delete: :cascade
@@ -2389,7 +2390,7 @@ ActiveRecord::Schema.define(version: 20181126153547) do
   add_foreign_key "project_import_data", "projects", name: "fk_ffb9ee3a10", on_delete: :cascade
   add_foreign_key "project_mirror_data", "projects", on_delete: :cascade
   add_foreign_key "project_statistics", "projects", on_delete: :cascade
-  add_foreign_key "projects", "repositories", column: "pool_repository_id", name: "fk_6e5c14658a", on_delete: :nullify
+  add_foreign_key "projects", "pool_repositories", name: "fk_6e5c14658a", on_delete: :nullify
   add_foreign_key "prometheus_metrics", "projects", on_delete: :cascade
   add_foreign_key "protected_branch_merge_access_levels", "protected_branches", name: "fk_8a3072ccb3", on_delete: :cascade
   add_foreign_key "protected_branch_push_access_levels", "protected_branches", name: "fk_9ffc86a3d9", on_delete: :cascade
@@ -2401,7 +2402,6 @@ ActiveRecord::Schema.define(version: 20181126153547) do
   add_foreign_key "push_event_payloads", "events", name: "fk_36c74129da", on_delete: :cascade
   add_foreign_key "releases", "projects", name: "fk_47fe2a0596", on_delete: :cascade
   add_foreign_key "remote_mirrors", "projects", on_delete: :cascade
-  add_foreign_key "repositories", "shards", on_delete: :restrict
   add_foreign_key "repository_languages", "projects", on_delete: :cascade
   add_foreign_key "resource_label_events", "issues", on_delete: :cascade
   add_foreign_key "resource_label_events", "labels", on_delete: :nullify

lib/tasks/gitlab/cleanup.rake

@@ -6,7 +6,7 @@ namespace :gitlab do
     desc "GitLab | Cleanup | Clean namespaces"
     task dirs: :gitlab_environment do
       namespaces = Set.new(Namespace.pluck(:path))
-      namespaces << Storage::HashedProject::ROOT_PATH_PREFIX
+      namespaces << Storage::HashedProject::REPOSITORY_PATH_PREFIX
 
       Gitaly::Server.all.each do |server|
         all_dirs = Gitlab::GitalyClient::StorageService
@@ -49,7 +49,7 @@ namespace :gitlab do
 
           # TODO ignoring hashed repositories for now.  But revisit to fully support
           # possible orphaned hashed repos
-          next if repo_with_namespace.start_with?(Storage::HashedProject::ROOT_PATH_PREFIX)
+          next if repo_with_namespace.start_with?(Storage::HashedProject::REPOSITORY_PATH_PREFIX)
           next if Project.find_by_full_path(repo_with_namespace)
 
           new_path = path + move_suffix

spec/factories/pool_repositories.rb

+FactoryBot.define do
+  factory :pool_repository do
+    shard
+  end
+end

spec/factories/shards.rb

+FactoryBot.define do
+  factory :shard do
+    name "default"
+  end
+end

spec/models/pool_repository_spec.rb

+require 'spec_helper'
+
+describe PoolRepository do
+  describe 'associations' do
+    it { is_expected.to belong_to(:shard) }
+    it { is_expected.to have_many(:member_projects) }
+  end
+
+  describe 'validations' do
+    let!(:pool_repository) { create(:pool_repository) }
+
+    it { is_expected.to validate_presence_of(:shard) }
+  end
+
+  describe '#disk_path' do
+    it 'sets the hashed disk_path' do
+      pool = create(:pool_repository)
+
+      elements = File.split(pool.disk_path)
+
+      expect(elements).to all( match(/\d{2,}/) )
+    end
+  end
+end