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.

3 files changed, 87 insertions, 68 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