Add many foreign keys to the projects table

This removes the need for relying on Rails' "dependent" option for data
removal, which is _incredibly_ slow (even when using :delete_all) when
deleting large amounts of data. This also ensures data consistency is
enforced on DB level and not on application level (something Rails is
really bad at).

This commit also includes various migrations to add foreign keys to
tables that eventually point to "projects" to ensure no rows get
orphaned upon removing a project.

14 files changed, 458 insertions, 146 deletions

diff --git a/app/models/issue.rb b/app/models/issue.rb
index a97e88f76f6..31e3504e535 100644
--- a/app/models/issue.rb
+++ b/app/models/issue.rb
@@ -25,7 +25,7 @@ class Issue < ActiveRecord::Base
 
   has_many :events, as: :target, dependent: :destroy
 
-  has_many :merge_requests_closing_issues, class_name: 'MergeRequestsClosingIssues', dependent: :delete_all
+  has_many :merge_requests_closing_issues, class_name: 'MergeRequestsClosingIssues'
 
   has_many :issue_assignees
   has_many :assignees, class_name: "User", through: :issue_assignees
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 808212c780c..d2534e9c858 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -12,7 +12,7 @@ class MergeRequest < ActiveRecord::Base
   belongs_to :source_project, class_name: "Project"
   belongs_to :merge_user, class_name: "User"
 
-  has_many :merge_request_diffs, dependent: :destroy
+  has_many :merge_request_diffs
   has_one :merge_request_diff,
     -> { order('merge_request_diffs.id DESC') }
 
@@ -20,7 +20,7 @@ class MergeRequest < ActiveRecord::Base
 
   has_many :events, as: :target, dependent: :destroy
 
-  has_many :merge_requests_closing_issues, class_name: 'MergeRequestsClosingIssues', dependent: :delete_all
+  has_many :merge_requests_closing_issues, class_name: 'MergeRequestsClosingIssues'
 
   belongs_to :assignee, class_name: "User"
 
diff --git a/app/models/project.rb b/app/models/project.rb
index 3a5a01db518..181e9940ddb 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -59,6 +59,7 @@ class Project < ActiveRecord::Base
     update_column(:last_repository_updated_at, self.created_at)
   end
 
+  before_destroy :remove_private_deploy_keys
   after_destroy :remove_pages
 
   # update visibility_level of forks
@@ -80,96 +81,108 @@ class Project < ActiveRecord::Base
   belongs_to :namespace
 
   has_one :last_event, -> {order 'events.created_at DESC'}, class_name: 'Event'
-  has_many :boards, before_add: :validate_board_limit, dependent: :destroy
+  has_many :boards, before_add: :validate_board_limit
 
   # Project services
-  has_one :campfire_service, dependent: :destroy
-  has_one :drone_ci_service, dependent: :destroy
-  has_one :emails_on_push_service, dependent: :destroy
-  has_one :pipelines_email_service, dependent: :destroy
-  has_one :irker_service, dependent: :destroy
-  has_one :pivotaltracker_service, dependent: :destroy
-  has_one :hipchat_service, dependent: :destroy
-  has_one :flowdock_service, dependent: :destroy
-  has_one :assembla_service, dependent: :destroy
-  has_one :asana_service, dependent: :destroy
-  has_one :gemnasium_service, dependent: :destroy
-  has_one :mattermost_slash_commands_service, dependent: :destroy
-  has_one :mattermost_service, dependent: :destroy
-  has_one :slack_slash_commands_service, dependent: :destroy
-  has_one :slack_service, dependent: :destroy
-  has_one :buildkite_service, dependent: :destroy
-  has_one :bamboo_service, dependent: :destroy
-  has_one :teamcity_service, dependent: :destroy
-  has_one :pushover_service, dependent: :destroy
-  has_one :jira_service, dependent: :destroy
-  has_one :redmine_service, dependent: :destroy
-  has_one :custom_issue_tracker_service, dependent: :destroy
-  has_one :bugzilla_service, dependent: :destroy
-  has_one :gitlab_issue_tracker_service, dependent: :destroy, inverse_of: :project
-  has_one :external_wiki_service, dependent: :destroy
-  has_one :kubernetes_service, dependent: :destroy, inverse_of: :project
-  has_one :prometheus_service, dependent: :destroy, inverse_of: :project
-  has_one :mock_ci_service, dependent: :destroy
-  has_one :mock_deployment_service, dependent: :destroy
-  has_one :mock_monitoring_service, dependent: :destroy
-  has_one :microsoft_teams_service, dependent: :destroy
-
-  has_one  :forked_project_link,  dependent: :destroy, foreign_key: "forked_to_project_id"
+  has_one :campfire_service
+  has_one :drone_ci_service
+  has_one :emails_on_push_service
+  has_one :pipelines_email_service
+  has_one :irker_service
+  has_one :pivotaltracker_service
+  has_one :hipchat_service
+  has_one :flowdock_service
+  has_one :assembla_service
+  has_one :asana_service
+  has_one :gemnasium_service
+  has_one :mattermost_slash_commands_service
+  has_one :mattermost_service
+  has_one :slack_slash_commands_service
+  has_one :slack_service
+  has_one :buildkite_service
+  has_one :bamboo_service
+  has_one :teamcity_service
+  has_one :pushover_service
+  has_one :jira_service
+  has_one :redmine_service
+  has_one :custom_issue_tracker_service
+  has_one :bugzilla_service
+  has_one :gitlab_issue_tracker_service, inverse_of: :project
+  has_one :external_wiki_service
+  has_one :kubernetes_service, inverse_of: :project
+  has_one :prometheus_service, inverse_of: :project
+  has_one :mock_ci_service
+  has_one :mock_deployment_service
+  has_one :mock_monitoring_service
+  has_one :microsoft_teams_service
+
+  has_one  :forked_project_link,  foreign_key: "forked_to_project_id"
   has_one  :forked_from_project,  through:   :forked_project_link
 
   has_many :forked_project_links, foreign_key: "forked_from_project_id"
   has_many :forks,                through:     :forked_project_links, source: :forked_to_project
 
   # Merge Requests for target project should be removed with it
-  has_many :merge_requests,     dependent: :destroy, foreign_key: 'target_project_id'
-  has_many :issues,             dependent: :destroy
-  has_many :labels,             dependent: :destroy, class_name: 'ProjectLabel'
-  has_many :services,           dependent: :destroy
-  has_many :events,             dependent: :destroy
-  has_many :milestones,         dependent: :destroy
-  has_many :notes,              dependent: :destroy
-  has_many :snippets,           dependent: :destroy, class_name: 'ProjectSnippet'
-  has_many :hooks,              dependent: :destroy, class_name: 'ProjectHook'
-  has_many :protected_branches, dependent: :destroy
-  has_many :protected_tags,     dependent: :destroy
+  has_many :merge_requests, foreign_key: 'target_project_id'
+  has_many :issues
+  has_many :labels, class_name: 'ProjectLabel'
+  has_many :services
+  has_many :events
+  has_many :milestones
+  has_many :notes
+  has_many :snippets, class_name: 'ProjectSnippet'
+  has_many :hooks, class_name: 'ProjectHook'
+  has_many :protected_branches
+  has_many :protected_tags
 
   has_many :project_authorizations
   has_many :authorized_users, through: :project_authorizations, source: :user, class_name: 'User'
-  has_many :project_members, -> { where(requested_at: nil) }, dependent: :destroy, as: :source
+  has_many :project_members, -> { where(requested_at: nil) },
+    as: :source, dependent: :delete_all
+
   alias_method :members, :project_members
   has_many :users, through: :project_members
 
-  has_many :requesters, -> { where.not(requested_at: nil) }, dependent: :destroy, as: :source, class_name: 'ProjectMember'
+  has_many :requesters, -> { where.not(requested_at: nil) },
+    as: :source, class_name: 'ProjectMember', dependent: :delete_all
 
-  has_many :deploy_keys_projects, dependent: :destroy
+  has_many :deploy_keys_projects
   has_many :deploy_keys, through: :deploy_keys_projects
-  has_many :users_star_projects, dependent: :destroy
+  has_many :users_star_projects
   has_many :starrers, through: :users_star_projects, source: :user
-  has_many :releases, dependent: :destroy
+  has_many :releases
   has_many :lfs_objects_projects, dependent: :destroy
   has_many :lfs_objects, through: :lfs_objects_projects
-  has_many :project_group_links, dependent: :destroy
+  has_many :project_group_links
   has_many :invited_groups, through: :project_group_links, source: :group
-  has_many :pages_domains, dependent: :destroy
-  has_many :todos, dependent: :destroy
-  has_many :notification_settings, dependent: :destroy, as: :source
+  has_many :pages_domains
+  has_many :todos
+  has_many :notification_settings, as: :source, dependent: :delete_all
+
+  has_one :import_data, class_name: 'ProjectImportData'
+  has_one :project_feature
+  has_one :statistics, class_name: 'ProjectStatistics'
 
-  has_one :import_data, dependent: :delete, class_name: 'ProjectImportData'
-  has_one :project_feature, dependent: :destroy
-  has_one :statistics, class_name: 'ProjectStatistics', dependent: :delete
+  # Container repositories need to remove data from the container registry,
+  # which is not managed by the DB. Hence we're still using dependent: :destroy
+  # here.
   has_many :container_repositories, dependent: :destroy
 
-  has_many :commit_statuses, dependent: :destroy
-  has_many :pipelines, dependent: :destroy, class_name: 'Ci::Pipeline'
-  has_many :builds, class_name: 'Ci::Build' # the builds are created from the commit_statuses
-  has_many :runner_projects, dependent: :destroy, class_name: 'Ci::RunnerProject'
+  has_many :commit_statuses
+  has_many :pipelines, class_name: 'Ci::Pipeline'
+
+  # Ci::Build objects store data on the file system such as artifact files and
+  # build traces. Currently there's no efficient way of removing this data in
+  # bulk that doesn't involve loading the rows into memory. As a result we're
+  # still using `dependent: :destroy` here.
+  has_many :builds, class_name: 'Ci::Build', dependent: :destroy
+  has_many :runner_projects, class_name: 'Ci::RunnerProject'
   has_many :runners, through: :runner_projects, source: :runner, class_name: 'Ci::Runner'
   has_many :variables, class_name: 'Ci::Variable'
-  has_many :triggers, dependent: :destroy, class_name: 'Ci::Trigger'
-  has_many :environments, dependent: :destroy
-  has_many :deployments, dependent: :destroy
-  has_many :pipeline_schedules, dependent: :destroy, class_name: 'Ci::PipelineSchedule'
+  has_many :triggers, class_name: 'Ci::Trigger'
+  has_many :environments
+  has_many :deployments
+  has_many :pipeline_schedules, class_name: 'Ci::PipelineSchedule'
 
   has_many :active_runners, -> { active }, through: :runner_projects, source: :runner, class_name: 'Ci::Runner'
 
@@ -1240,7 +1253,13 @@ class Project < ActiveRecord::Base
     File.join(pages_path, 'public')
   end
 
+  def remove_private_deploy_keys
+    deploy_keys.where(public: false).delete_all
+  end
+
   def remove_pages
+    ::Projects::UpdatePagesConfigurationService.new(self).execute
+
     # 1. We rename pages to temporary directory
     # 2. We wait 5 minutes, due to NFS caching
     # 3. We asynchronously remove pages with force
diff --git a/changelogs/unreleased/foreign-keys-for-project-model.yml b/changelogs/unreleased/foreign-keys-for-project-model.yml
new file mode 100644
index 00000000000..3648b1c3735
--- /dev/null
+++ b/changelogs/unreleased/foreign-keys-for-project-model.yml
@@ -0,0 +1,4 @@
+---
+title: Speed up project removals by adding foreign keys with cascading deletes to various tables
+merge_request:
+author:
diff --git a/db/migrate/20170530130129_project_foreign_keys_with_cascading_deletes.rb b/db/migrate/20170530130129_project_foreign_keys_with_cascading_deletes.rb
new file mode 100644
index 00000000000..3eaafac321d
--- /dev/null
+++ b/db/migrate/20170530130129_project_foreign_keys_with_cascading_deletes.rb
@@ -0,0 +1,187 @@
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class ProjectForeignKeysWithCascadingDeletes < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  CONCURRENCY = 4
+
+  disable_ddl_transaction!
+
+  # The tables/columns for which to remove orphans and add foreign keys. Order
+  # matters as some tables/columns should be processed before others.
+  TABLES = [
+    [:boards, :projects, :project_id],
+    [:lists, :labels, :label_id],
+    [:lists, :boards, :board_id],
+    [:services, :projects, :project_id],
+    [:forked_project_links, :projects, :forked_to_project_id],
+    [:merge_requests, :projects, :target_project_id],
+    [:labels, :projects, :project_id],
+    [:issues, :projects, :project_id],
+    [:events, :projects, :project_id],
+    [:milestones, :projects, :project_id],
+    [:notes, :projects, :project_id],
+    [:snippets, :projects, :project_id],
+    [:web_hooks, :projects, :project_id],
+    [:protected_branch_merge_access_levels, :protected_branches, :protected_branch_id],
+    [:protected_branch_push_access_levels, :protected_branches, :protected_branch_id],
+    [:protected_branches, :projects, :project_id],
+    [:protected_tags, :projects, :project_id],
+    [:deploy_keys_projects, :projects, :project_id],
+    [:users_star_projects, :projects, :project_id],
+    [:releases, :projects, :project_id],
+    [:project_group_links, :projects, :project_id],
+    [:pages_domains, :projects, :project_id],
+    [:todos, :projects, :project_id],
+    [:project_import_data, :projects, :project_id],
+    [:project_features, :projects, :project_id],
+    [:ci_builds, :projects, :project_id],
+    [:ci_pipelines, :projects, :project_id],
+    [:ci_runner_projects, :projects, :project_id],
+    [:ci_triggers, :projects, :project_id],
+    [:environments, :projects, :project_id],
+    [:deployments, :projects, :project_id]
+  ]
+
+  def up
+    # These existing foreign keys don't have an "ON DELETE CASCADE" clause.
+    remove_foreign_key_without_error(:boards, :project_id)
+    remove_foreign_key_without_error(:lists, :label_id)
+    remove_foreign_key_without_error(:lists, :board_id)
+    remove_foreign_key_without_error(:protected_branch_merge_access_levels,
+                                     :protected_branch_id)
+
+    remove_foreign_key_without_error(:protected_branch_push_access_levels,
+                                     :protected_branch_id)
+
+    remove_orphaned_rows
+    add_foreign_keys
+
+    # These columns are not indexed yet, meaning a cascading delete would take
+    # forever.
+    add_concurrent_index(:project_group_links, :project_id)
+    add_concurrent_index(:pages_domains, :project_id)
+  end
+
+  def down
+    TABLES.each do |(source, _, column)|
+      remove_foreign_key_without_error(source, column)
+    end
+
+    add_concurrent_foreign_key(:boards, :projects, column: :project_id)
+    add_concurrent_foreign_key(:lists, :labels, column: :label_id)
+    add_concurrent_foreign_key(:lists, :boards, column: :board_id)
+
+    add_concurrent_foreign_key(:protected_branch_merge_access_levels,
+                               :protected_branches,
+                               column: :protected_branch_id)
+
+    add_concurrent_foreign_key(:protected_branch_push_access_levels,
+                               :protected_branches,
+                               column: :protected_branch_id)
+
+    remove_index_without_error(:project_group_links, :project_id)
+    remove_index_without_error(:pages_domains, :project_id)
+  end
+
+  def add_foreign_keys
+    TABLES.each do |(source, target, column)|
+      add_concurrent_foreign_key(source, target, column: column)
+    end
+  end
+
+  # Removes orphans from various tables concurrently.
+  def remove_orphaned_rows
+    Gitlab::Database.with_connection_pool(CONCURRENCY) do |pool|
+      queues = queues_for_rows(TABLES)
+
+      threads = queues.map do |queue|
+        Thread.new do
+          pool.with_connection do |connection|
+            Thread.current[:foreign_key_connection] = connection
+
+            # Disables statement timeouts for the current connection. This is
+            # necessary as removing of orphaned data might otherwise exceed the
+            # statement timeout.
+            disable_statement_timeout
+
+            remove_orphans(*queue.pop) until queue.empty?
+
+            steal_from_queues(queues - [queue])
+          end
+        end
+      end
+
+      threads.each(&:join)
+    end
+  end
+
+  def steal_from_queues(queues)
+    loop do
+      stolen = false
+
+      queues.each do |queue|
+        # Stealing is racy so it's possible a pop might be called on an
+        # already-empty queue.
+        begin
+          remove_orphans(*queue.pop(true))
+          stolen = true
+        rescue ThreadError
+        end
+      end
+
+      break unless stolen
+    end
+  end
+
+  def remove_orphans(source, target, column)
+    quoted_source = quote_table_name(source)
+    quoted_target = quote_table_name(target)
+    quoted_column = quote_column_name(column)
+
+    execute <<-EOF.strip_heredoc
+    DELETE FROM #{quoted_source}
+    WHERE NOT EXISTS (
+      SELECT true
+      FROM #{quoted_target}
+      WHERE #{quoted_target}.id = #{quoted_source}.#{quoted_column}
+    )
+    AND #{quoted_source}.#{quoted_column} IS NOT NULL
+    EOF
+  end
+
+  def remove_foreign_key_without_error(table, column)
+    remove_foreign_key(table, column: column)
+  rescue ArgumentError
+  end
+
+  def remove_index_without_error(table, column)
+    remove_concurrent_index(table, column)
+  rescue ArgumentError
+  end
+
+  def connection
+    # Rails memoizes connection objects, but this causes them to be shared
+    # amongst threads; we don't want that.
+    Thread.current[:foreign_key_connection] || ActiveRecord::Base.connection
+  end
+
+  def queues_for_rows(rows)
+    queues = Array.new(CONCURRENCY) { Queue.new }
+    slice_size = rows.length / CONCURRENCY
+
+    # Divide all the tuples as evenly as possible amongst the queues.
+    rows.each_slice(slice_size).each_with_index do |slice, index|
+      bucket = index % CONCURRENCY
+
+      slice.each do |row|
+        queues[bucket] << row
+      end
+    end
+
+    queues
+  end
+end
diff --git a/db/migrate/20170622130029_correct_protected_branches_foreign_keys.rb b/db/migrate/20170622130029_correct_protected_branches_foreign_keys.rb
new file mode 100644
index 00000000000..46497775527
--- /dev/null
+++ b/db/migrate/20170622130029_correct_protected_branches_foreign_keys.rb
@@ -0,0 +1,40 @@
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class CorrectProtectedBranchesForeignKeys < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    remove_foreign_key_without_error(:protected_branch_push_access_levels,
+                                     column: :protected_branch_id)
+
+    execute <<-EOF
+    DELETE FROM protected_branch_push_access_levels
+    WHERE NOT EXISTS (
+      SELECT true
+      FROM protected_branches
+      WHERE protected_branch_push_access_levels.protected_branch_id = protected_branches.id
+    )
+    AND protected_branch_id IS NOT NULL
+    EOF
+
+    add_concurrent_foreign_key(:protected_branch_push_access_levels,
+                               :protected_branches,
+                               column: :protected_branch_id)
+  end
+
+  def down
+    # Previously there was a foreign key without a CASCADING DELETE, so we'll
+    # just leave the foreign key in place.
+  end
+
+  def remove_foreign_key_without_error(*args)
+    remove_foreign_key(*args)
+  rescue ArgumentError
+  end
+end
diff --git a/db/migrate/20170622132212_add_foreign_key_for_merge_request_diffs.rb b/db/migrate/20170622132212_add_foreign_key_for_merge_request_diffs.rb
new file mode 100644
index 00000000000..9f524fac8a7
--- /dev/null
+++ b/db/migrate/20170622132212_add_foreign_key_for_merge_request_diffs.rb
@@ -0,0 +1,30 @@
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddForeignKeyForMergeRequestDiffs < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    execute <<-EOF
+    DELETE FROM merge_request_diffs
+    WHERE NOT EXISTS (
+      SELECT true
+      FROM merge_requests
+      WHERE merge_requests.id = merge_request_diffs.merge_request_id
+    )
+    EOF
+
+    add_concurrent_foreign_key(:merge_request_diffs,
+                               :merge_requests,
+                               column: :merge_request_id)
+  end
+
+  def down
+    remove_foreign_key(:merge_request_diffs, column: :merge_request_id)
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 40f30a10a01..f12fdf903c5 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -971,6 +971,7 @@ ActiveRecord::Schema.define(version: 20170703102400) do
   end
 
   add_index "pages_domains", ["domain"], name: "index_pages_domains_on_domain", unique: true, using: :btree
+  add_index "pages_domains", ["project_id"], name: "index_pages_domains_on_project_id", using: :btree
 
   create_table "personal_access_tokens", force: :cascade do |t|
     t.integer "user_id", null: false
@@ -1020,6 +1021,7 @@ ActiveRecord::Schema.define(version: 20170703102400) do
   end
 
   add_index "project_group_links", ["group_id"], name: "index_project_group_links_on_group_id", using: :btree
+  add_index "project_group_links", ["project_id"], name: "index_project_group_links_on_project_id", using: :btree
 
   create_table "project_import_data", force: :cascade do |t|
     t.integer "project_id"
@@ -1528,48 +1530,75 @@ ActiveRecord::Schema.define(version: 20170703102400) do
   add_index "web_hooks", ["project_id"], name: "index_web_hooks_on_project_id", using: :btree
   add_index "web_hooks", ["type"], name: "index_web_hooks_on_type", using: :btree
 
-  add_foreign_key "boards", "projects"
+  add_foreign_key "boards", "projects", name: "fk_f15266b5f9", on_delete: :cascade
   add_foreign_key "chat_teams", "namespaces", on_delete: :cascade
   add_foreign_key "ci_builds", "ci_pipelines", column: "auto_canceled_by_id", name: "fk_a2141b1522", on_delete: :nullify
   add_foreign_key "ci_builds", "ci_stages", column: "stage_id", name: "fk_3a9eaa254d", on_delete: :cascade
+  add_foreign_key "ci_builds", "projects", name: "fk_befce0568a", on_delete: :cascade
   add_foreign_key "ci_pipeline_schedules", "projects", name: "fk_8ead60fcc4", on_delete: :cascade
   add_foreign_key "ci_pipeline_schedules", "users", column: "owner_id", name: "fk_9ea99f58d2", on_delete: :nullify
   add_foreign_key "ci_pipelines", "ci_pipeline_schedules", column: "pipeline_schedule_id", name: "fk_3d34ab2e06", on_delete: :nullify
   add_foreign_key "ci_pipelines", "ci_pipelines", column: "auto_canceled_by_id", name: "fk_262d4c2d19", on_delete: :nullify
+  add_foreign_key "ci_pipelines", "projects", name: "fk_86635dbd80", on_delete: :cascade
+  add_foreign_key "ci_runner_projects", "projects", name: "fk_4478a6f1e4", on_delete: :cascade
   add_foreign_key "ci_stages", "ci_pipelines", column: "pipeline_id", name: "fk_fb57e6cc56", on_delete: :cascade
   add_foreign_key "ci_stages", "projects", name: "fk_2360681d1d", on_delete: :cascade
   add_foreign_key "ci_trigger_requests", "ci_triggers", column: "trigger_id", name: "fk_b8ec8b7245", on_delete: :cascade
+  add_foreign_key "ci_triggers", "projects", name: "fk_e3e63f966e", on_delete: :cascade
   add_foreign_key "ci_triggers", "users", column: "owner_id", name: "fk_e8e10d1964", on_delete: :cascade
   add_foreign_key "ci_variables", "projects", name: "fk_ada5eb64b3", on_delete: :cascade
   add_foreign_key "container_repositories", "projects"
+  add_foreign_key "deploy_keys_projects", "projects", name: "fk_58a901ca7e", on_delete: :cascade
+  add_foreign_key "deployments", "projects", name: "fk_b9a3851b82", on_delete: :cascade
+  add_foreign_key "environments", "projects", name: "fk_d1c8c1da6a", on_delete: :cascade
+  add_foreign_key "events", "projects", name: "fk_0434b48643", on_delete: :cascade
+  add_foreign_key "forked_project_links", "projects", column: "forked_to_project_id", name: "fk_434510edb0", on_delete: :cascade
   add_foreign_key "issue_assignees", "issues", name: "fk_b7d881734a", on_delete: :cascade
   add_foreign_key "issue_assignees", "users", name: "fk_5e0c8d9154", on_delete: :cascade
   add_foreign_key "issue_metrics", "issues", on_delete: :cascade
+  add_foreign_key "issues", "projects", name: "fk_899c8f3231", on_delete: :cascade
   add_foreign_key "label_priorities", "labels", on_delete: :cascade
   add_foreign_key "label_priorities", "projects", on_delete: :cascade
   add_foreign_key "labels", "namespaces", column: "group_id", on_delete: :cascade
-  add_foreign_key "lists", "boards"
-  add_foreign_key "lists", "labels"
+  add_foreign_key "labels", "projects", name: "fk_7de4989a69", on_delete: :cascade
+  add_foreign_key "lists", "boards", name: "fk_0d3f677137", on_delete: :cascade
+  add_foreign_key "lists", "labels", name: "fk_7a5553d60f", on_delete: :cascade
   add_foreign_key "merge_request_diff_files", "merge_request_diffs", on_delete: :cascade
+  add_foreign_key "merge_request_diffs", "merge_requests", name: "fk_8483f3258f", on_delete: :cascade
   add_foreign_key "merge_request_metrics", "ci_pipelines", column: "pipeline_id", on_delete: :cascade
   add_foreign_key "merge_request_metrics", "merge_requests", on_delete: :cascade
+  add_foreign_key "merge_requests", "projects", column: "target_project_id", name: "fk_a6963e8447", on_delete: :cascade
   add_foreign_key "merge_requests_closing_issues", "issues", on_delete: :cascade
   add_foreign_key "merge_requests_closing_issues", "merge_requests", on_delete: :cascade
+  add_foreign_key "milestones", "projects", name: "fk_9bd0a0c791", on_delete: :cascade
+  add_foreign_key "notes", "projects", name: "fk_99e097b079", on_delete: :cascade
   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 "project_authorizations", "projects", on_delete: :cascade
   add_foreign_key "project_authorizations", "users", on_delete: :cascade
+  add_foreign_key "project_features", "projects", name: "fk_18513d9b92", on_delete: :cascade
+  add_foreign_key "project_group_links", "projects", name: "fk_daa8cee94c", on_delete: :cascade
+  add_foreign_key "project_import_data", "projects", name: "fk_ffb9ee3a10", on_delete: :cascade
   add_foreign_key "project_statistics", "projects", on_delete: :cascade
-  add_foreign_key "protected_branch_merge_access_levels", "protected_branches"
-  add_foreign_key "protected_branch_push_access_levels", "protected_branches"
+  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
+  add_foreign_key "protected_branches", "projects", name: "fk_7a9c6d93e7", on_delete: :cascade
   add_foreign_key "protected_tag_create_access_levels", "namespaces", column: "group_id"
   add_foreign_key "protected_tag_create_access_levels", "protected_tags"
   add_foreign_key "protected_tag_create_access_levels", "users"
+  add_foreign_key "protected_tags", "projects", name: "fk_8e4af87648", on_delete: :cascade
+  add_foreign_key "releases", "projects", name: "fk_47fe2a0596", on_delete: :cascade
+  add_foreign_key "services", "projects", name: "fk_71cce407f9", on_delete: :cascade
+  add_foreign_key "snippets", "projects", name: "fk_be41fd4bb7", on_delete: :cascade
   add_foreign_key "subscriptions", "projects", on_delete: :cascade
   add_foreign_key "system_note_metadata", "notes", name: "fk_d83a918cb1", on_delete: :cascade
   add_foreign_key "timelogs", "issues", name: "fk_timelogs_issues_issue_id", on_delete: :cascade
   add_foreign_key "timelogs", "merge_requests", name: "fk_timelogs_merge_requests_merge_request_id", on_delete: :cascade
+  add_foreign_key "todos", "projects", name: "fk_45054f9c45", on_delete: :cascade
   add_foreign_key "trending_projects", "projects", on_delete: :cascade
   add_foreign_key "u2f_registrations", "users"
+  add_foreign_key "users_star_projects", "projects", name: "fk_22cd27ddfc", on_delete: :cascade
   add_foreign_key "web_hook_logs", "web_hooks", on_delete: :cascade
+  add_foreign_key "web_hooks", "projects", name: "fk_0c8ca6d9d1", on_delete: :cascade
 end
diff --git a/spec/models/concerns/issuable_spec.rb b/spec/models/concerns/issuable_spec.rb
index ac9303370ab..505039c9d88 100644
--- a/spec/models/concerns/issuable_spec.rb
+++ b/spec/models/concerns/issuable_spec.rb
@@ -155,7 +155,7 @@ describe Issuable do
   end
 
   describe "#sort" do
-    let(:project) { build_stubbed(:empty_project) }
+    let(:project) { create(:empty_project) }
 
     context "by milestone due date" do
       # Correct order is:
diff --git a/spec/models/forked_project_link_spec.rb b/spec/models/forked_project_link_spec.rb
index 5c13cf584f9..38fbdd2536a 100644
--- a/spec/models/forked_project_link_spec.rb
+++ b/spec/models/forked_project_link_spec.rb
@@ -42,7 +42,7 @@ describe ForkedProjectLink, "add link on fork" do
 
   describe '#forked?' do
     let(:project_to) { create(:project, forked_project_link: forked_project_link) }
-    let(:forked_project_link) { build(:forked_project_link) }
+    let(:forked_project_link) { create(:forked_project_link) }
 
     before do
       forked_project_link.forked_from_project = project_from
@@ -59,9 +59,9 @@ describe ForkedProjectLink, "add link on fork" do
     end
 
     it "project_to.destroy destroys fork_link" do
-      expect(forked_project_link).to receive(:destroy)
-
       project_to.destroy
+
+      expect(ForkedProjectLink.exists?(id: forked_project_link.id)).to eq(false)
     end
   end
 
diff --git a/spec/models/merge_request_spec.rb b/spec/models/merge_request_spec.rb
index 587d4b83cb4..d91f1f1a11c 100644
--- a/spec/models/merge_request_spec.rb
+++ b/spec/models/merge_request_spec.rb
@@ -10,7 +10,7 @@ describe MergeRequest, models: true do
     it { is_expected.to belong_to(:source_project).class_name('Project') }
     it { is_expected.to belong_to(:merge_user).class_name("User") }
     it { is_expected.to belong_to(:assignee) }
-    it { is_expected.to have_many(:merge_request_diffs).dependent(:destroy) }
+    it { is_expected.to have_many(:merge_request_diffs) }
   end
 
   describe 'modules' do
diff --git a/spec/models/project_spec.rb b/spec/models/project_spec.rb
index f50b4aea411..75fa2d2eb46 100644
--- a/spec/models/project_spec.rb
+++ b/spec/models/project_spec.rb
@@ -7,50 +7,50 @@ describe Project, models: true do
     it { is_expected.to belong_to(:creator).class_name('User') }
     it { is_expected.to have_many(:users) }
     it { is_expected.to have_many(:services) }
-    it { is_expected.to have_many(:events).dependent(:destroy) }
-    it { is_expected.to have_many(:merge_requests).dependent(:destroy) }
-    it { is_expected.to have_many(:issues).dependent(:destroy) }
-    it { is_expected.to have_many(:milestones).dependent(:destroy) }
-    it { is_expected.to have_many(:project_members).dependent(:destroy) }
+    it { is_expected.to have_many(:events) }
+    it { is_expected.to have_many(:merge_requests) }
+    it { is_expected.to have_many(:issues) }
+    it { is_expected.to have_many(:milestones) }
+    it { is_expected.to have_many(:project_members).dependent(:delete_all) }
     it { is_expected.to have_many(:users).through(:project_members) }
-    it { is_expected.to have_many(:requesters).dependent(:destroy) }
-    it { is_expected.to have_many(:notes).dependent(:destroy) }
-    it { is_expected.to have_many(:snippets).class_name('ProjectSnippet').dependent(:destroy) }
-    it { is_expected.to have_many(:deploy_keys_projects).dependent(:destroy) }
+    it { is_expected.to have_many(:requesters).dependent(:delete_all) }
+    it { is_expected.to have_many(:notes) }
+    it { is_expected.to have_many(:snippets).class_name('ProjectSnippet') }
+    it { is_expected.to have_many(:deploy_keys_projects) }
     it { is_expected.to have_many(:deploy_keys) }
-    it { is_expected.to have_many(:hooks).dependent(:destroy) }
-    it { is_expected.to have_many(:protected_branches).dependent(:destroy) }
-    it { is_expected.to have_one(:forked_project_link).dependent(:destroy) }
-    it { is_expected.to have_one(:slack_service).dependent(:destroy) }
-    it { is_expected.to have_one(:microsoft_teams_service).dependent(:destroy) }
-    it { is_expected.to have_one(:mattermost_service).dependent(:destroy) }
-    it { is_expected.to have_one(:pushover_service).dependent(:destroy) }
-    it { is_expected.to have_one(:asana_service).dependent(:destroy) }
-    it { is_expected.to have_many(:boards).dependent(:destroy) }
-    it { is_expected.to have_one(:campfire_service).dependent(:destroy) }
-    it { is_expected.to have_one(:drone_ci_service).dependent(:destroy) }
-    it { is_expected.to have_one(:emails_on_push_service).dependent(:destroy) }
-    it { is_expected.to have_one(:pipelines_email_service).dependent(:destroy) }
-    it { is_expected.to have_one(:irker_service).dependent(:destroy) }
-    it { is_expected.to have_one(:pivotaltracker_service).dependent(:destroy) }
-    it { is_expected.to have_one(:hipchat_service).dependent(:destroy) }
-    it { is_expected.to have_one(:flowdock_service).dependent(:destroy) }
-    it { is_expected.to have_one(:assembla_service).dependent(:destroy) }
-    it { is_expected.to have_one(:slack_slash_commands_service).dependent(:destroy) }
-    it { is_expected.to have_one(:mattermost_slash_commands_service).dependent(:destroy) }
-    it { is_expected.to have_one(:gemnasium_service).dependent(:destroy) }
-    it { is_expected.to have_one(:buildkite_service).dependent(:destroy) }
-    it { is_expected.to have_one(:bamboo_service).dependent(:destroy) }
-    it { is_expected.to have_one(:teamcity_service).dependent(:destroy) }
-    it { is_expected.to have_one(:jira_service).dependent(:destroy) }
-    it { is_expected.to have_one(:redmine_service).dependent(:destroy) }
-    it { is_expected.to have_one(:custom_issue_tracker_service).dependent(:destroy) }
-    it { is_expected.to have_one(:bugzilla_service).dependent(:destroy) }
-    it { is_expected.to have_one(:gitlab_issue_tracker_service).dependent(:destroy) }
-    it { is_expected.to have_one(:external_wiki_service).dependent(:destroy) }
-    it { is_expected.to have_one(:project_feature).dependent(:destroy) }
-    it { is_expected.to have_one(:statistics).class_name('ProjectStatistics').dependent(:delete) }
-    it { is_expected.to have_one(:import_data).class_name('ProjectImportData').dependent(:delete) }
+    it { is_expected.to have_many(:hooks) }
+    it { is_expected.to have_many(:protected_branches) }
+    it { is_expected.to have_one(:forked_project_link) }
+    it { is_expected.to have_one(:slack_service) }
+    it { is_expected.to have_one(:microsoft_teams_service) }
+    it { is_expected.to have_one(:mattermost_service) }
+    it { is_expected.to have_one(:pushover_service) }
+    it { is_expected.to have_one(:asana_service) }
+    it { is_expected.to have_many(:boards) }
+    it { is_expected.to have_one(:campfire_service) }
+    it { is_expected.to have_one(:drone_ci_service) }
+    it { is_expected.to have_one(:emails_on_push_service) }
+    it { is_expected.to have_one(:pipelines_email_service) }
+    it { is_expected.to have_one(:irker_service) }
+    it { is_expected.to have_one(:pivotaltracker_service) }
+    it { is_expected.to have_one(:hipchat_service) }
+    it { is_expected.to have_one(:flowdock_service) }
+    it { is_expected.to have_one(:assembla_service) }
+    it { is_expected.to have_one(:slack_slash_commands_service) }
+    it { is_expected.to have_one(:mattermost_slash_commands_service) }
+    it { is_expected.to have_one(:gemnasium_service) }
+    it { is_expected.to have_one(:buildkite_service) }
+    it { is_expected.to have_one(:bamboo_service) }
+    it { is_expected.to have_one(:teamcity_service) }
+    it { is_expected.to have_one(:jira_service) }
+    it { is_expected.to have_one(:redmine_service) }
+    it { is_expected.to have_one(:custom_issue_tracker_service) }
+    it { is_expected.to have_one(:bugzilla_service) }
+    it { is_expected.to have_one(:gitlab_issue_tracker_service) }
+    it { is_expected.to have_one(:external_wiki_service) }
+    it { is_expected.to have_one(:project_feature) }
+    it { is_expected.to have_one(:statistics).class_name('ProjectStatistics') }
+    it { is_expected.to have_one(:import_data).class_name('ProjectImportData') }
     it { is_expected.to have_one(:last_event).class_name('Event') }
     it { is_expected.to have_one(:forked_from_project).through(:forked_project_link) }
     it { is_expected.to have_many(:commit_statuses) }
@@ -62,18 +62,18 @@ describe Project, models: true do
     it { is_expected.to have_many(:variables) }
     it { is_expected.to have_many(:triggers) }
     it { is_expected.to have_many(:pages_domains) }
-    it { is_expected.to have_many(:labels).class_name('ProjectLabel').dependent(:destroy) }
-    it { is_expected.to have_many(:users_star_projects).dependent(:destroy) }
-    it { is_expected.to have_many(:environments).dependent(:destroy) }
-    it { is_expected.to have_many(:deployments).dependent(:destroy) }
-    it { is_expected.to have_many(:todos).dependent(:destroy) }
-    it { is_expected.to have_many(:releases).dependent(:destroy) }
-    it { is_expected.to have_many(:lfs_objects_projects).dependent(:destroy) }
-    it { is_expected.to have_many(:project_group_links).dependent(:destroy) }
-    it { is_expected.to have_many(:notification_settings).dependent(:destroy) }
+    it { is_expected.to have_many(:labels).class_name('ProjectLabel') }
+    it { is_expected.to have_many(:users_star_projects) }
+    it { is_expected.to have_many(:environments) }
+    it { is_expected.to have_many(:deployments) }
+    it { is_expected.to have_many(:todos) }
+    it { is_expected.to have_many(:releases) }
+    it { is_expected.to have_many(:lfs_objects_projects) }
+    it { is_expected.to have_many(:project_group_links) }
+    it { is_expected.to have_many(:notification_settings).dependent(:delete_all) }
     it { is_expected.to have_many(:forks).through(:forked_project_links) }
     it { is_expected.to have_many(:uploads).dependent(:destroy) }
-    it { is_expected.to have_many(:pipeline_schedules).dependent(:destroy) }
+    it { is_expected.to have_many(:pipeline_schedules) }
 
     context 'after initialized' do
       it "has a project_feature" do
@@ -2199,4 +2199,21 @@ describe Project, models: true do
       end
     end
   end
+
+  describe '#remove_private_deploy_keys' do
+    it 'removes the private deploy keys of a project' do
+      project = create(:empty_project)
+
+      private_key = create(:deploy_key, public: false)
+      public_key = create(:deploy_key, public: true)
+
+      create(:deploy_keys_project, deploy_key: private_key, project: project)
+      create(:deploy_keys_project, deploy_key: public_key, project: project)
+
+      project.remove_private_deploy_keys
+
+      expect(project.deploy_keys.where(public: false).any?).to eq(false)
+      expect(project.deploy_keys.where(public: true).any?).to eq(true)
+    end
+  end
 end
diff --git a/spec/presenters/ci/build_presenter_spec.rb b/spec/presenters/ci/build_presenter_spec.rb
index 518e97d17a1..f05d5c7fce5 100644
--- a/spec/presenters/ci/build_presenter_spec.rb
+++ b/spec/presenters/ci/build_presenter_spec.rb
@@ -85,7 +85,7 @@ describe Ci::BuildPresenter do
 
   describe 'quack like a Ci::Build permission-wise' do
     context 'user is not allowed' do
-      let(:project) { build_stubbed(:empty_project, public_builds: false) }
+      let(:project) { create(:empty_project, public_builds: false) }
 
       it 'returns false' do
         expect(presenter.can?(nil, :read_build)).to be_falsy
@@ -93,7 +93,7 @@ describe Ci::BuildPresenter do
     end
 
     context 'user is allowed' do
-      let(:project) { build_stubbed(:empty_project, :public) }
+      let(:project) { create(:empty_project, :public) }
 
       it 'returns true' do
         expect(presenter.can?(nil, :read_build)).to be_truthy
diff --git a/spec/workers/expire_build_instance_artifacts_worker_spec.rb b/spec/workers/expire_build_instance_artifacts_worker_spec.rb
index 1d8da68883b..bed5c5e2ecb 100644
--- a/spec/workers/expire_build_instance_artifacts_worker_spec.rb
+++ b/spec/workers/expire_build_instance_artifacts_worker_spec.rb
@@ -30,20 +30,6 @@ describe ExpireBuildInstanceArtifactsWorker do
           expect(build.reload.artifacts_file_identifier).to be_nil
         end
       end
-
-      context 'when associated project was removed' do
-        let(:build) do
-          create(:ci_build, :artifacts, artifacts_expiry) do |build|
-            build.project.pending_delete = true
-          end
-        end
-
-        it 'does not remove artifacts' do
-          expect do
-            build.reload.artifacts_file
-          end.not_to raise_error
-        end
-      end
     end
 
     context 'with not yet expired artifacts' do