Smarter refreshing of authorized projectsproject-authorizations-diff

Prior to this commit the refreshing of authorized projects was done in
two steps:

1. Remove existing authorizations
2. Insert a new list of all authorizations

This can lead to a high amount of dead tuples as every time all rows are
being replaced. For example, if a user with 100 authorizations is given
access to a new project this would lead to:

* 100 rows being removed
* 101 new rows being inserted

This commit changes the way this system works so it only removes/inserts
what is necessary. Using the above example this would lead to only 1 new
row being inserted, with the initial 100 being left untouched.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/25257

1 files changed, 13 insertions, 0 deletions

diff --git a/app/models/project_authorization.rb b/app/models/project_authorization.rb
index a00d43773d9..4c7f4f5a429 100644
--- a/app/models/project_authorization.rb
+++ b/app/models/project_authorization.rb
@@ -5,4 +5,17 @@ class ProjectAuthorization < ActiveRecord::Base
   validates :project, presence: true
   validates :access_level, inclusion: { in: Gitlab::Access.all_values }, presence: true
   validates :user, uniqueness: { scope: [:project, :access_level] }, presence: true
+
+  def self.insert_authorizations(rows, per_batch = 1000)
+    rows.each_slice(per_batch) do |slice|
+      tuples = slice.map do |tuple|
+        tuple.map { |value| connection.quote(value) }
+      end
+
+      connection.execute <<-EOF.strip_heredoc
+      INSERT INTO project_authorizations (user_id, project_id, access_level)
+      VALUES #{tuples.map { |tuple| "(#{tuple.join(', ')})" }.join(', ')}
+      EOF
+    end
+  end
 end