Remove the project_authorizations.id column

This column used to be a 32 bits integer, allowing for only a maximum of
2 147 483 647 rows. Given enough users one can hit this limit pretty
quickly, as was the case for GitLab.com.

Changing this type to bigint (= 64 bits) would give us more space, but
we'd eventually hit the same limit given enough users and projects. A
much more sustainable solution is to simply drop the "id" column.

There were only 2 lines of code depending on this column being present,
and neither truly required it to be present. Instead the code now uses
the "project_id" column combined with the "user_id" column. This means
that instead of something like this:

    DELETE FROM project_authorizations
    WHERE user_id = X
    AND id = Y;

We now run the following when removing rows:

    DELETE FROM project_authorizations
    WHERE user_id = X
    AND project_id = Y;

Since both user_id and project_id are indexed this should not slow down
the DELETE query.

This commit also removes the "dependent: destroy" clause from the
"project_authorizations" relation in the User and Project models.
Keeping this prevents Rails from being able to remove data as it relies
on an "id" column being present. Since the "project_authorizations"
table has proper foreign keys set up (with cascading removals) we don't
need to depend on any Rails logic.

3 files changed, 5 insertions, 5 deletions

diff --git a/app/models/project.rb b/app/models/project.rb
index ec40def6fb1..94a6f3ba799 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -130,7 +130,7 @@ class Project < ActiveRecord::Base
   has_many :hooks,              dependent: :destroy, class_name: 'ProjectHook'
   has_many :protected_branches, dependent: :destroy
 
-  has_many :project_authorizations, dependent: :destroy
+  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
   alias_method :members, :project_members
diff --git a/app/models/user.rb b/app/models/user.rb
index 66a768d54bb..06dd98a3188 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -73,7 +73,7 @@ class User < ActiveRecord::Base
   has_many :created_projects,         foreign_key: :creator_id, class_name: 'Project'
   has_many :users_star_projects, dependent: :destroy
   has_many :starred_projects, through: :users_star_projects, source: :project
-  has_many :project_authorizations, dependent: :destroy
+  has_many :project_authorizations
   has_many :authorized_projects, through: :project_authorizations, source: :project
 
   has_many :snippets,                 dependent: :destroy, foreign_key: :author_id
@@ -444,7 +444,7 @@ class User < ActiveRecord::Base
   end
 
   def remove_project_authorizations(project_ids)
-    project_authorizations.where(id: project_ids).delete_all
+    project_authorizations.where(project_id: project_ids).delete_all
   end
 
   def set_authorized_projects_column
diff --git a/app/services/users/refresh_authorized_projects_service.rb b/app/services/users/refresh_authorized_projects_service.rb
index 8559908e0c3..21ec1bd9e65 100644
--- a/app/services/users/refresh_authorized_projects_service.rb
+++ b/app/services/users/refresh_authorized_projects_service.rb
@@ -35,7 +35,7 @@ module Users
         # rows not in the new list or with a different access level should be
         # removed.
         if !fresh[project_id] || fresh[project_id] != row.access_level
-          array << row.id
+          array << row.project_id
         end
       end
 
@@ -100,7 +100,7 @@ module Users
     end
 
     def current_authorizations
-      user.project_authorizations.select(:id, :project_id, :access_level)
+      user.project_authorizations.select(:project_id, :access_level)
     end
 
     def fresh_authorizations