1 files changed, 52 insertions, 0 deletions
diff --git a/lib/gitlab/background_migration/backfill_ci_project_mirrors.rb b/lib/gitlab/background_migration/backfill_ci_project_mirrors.rb
new file mode 100644
index 00000000000..ff6ab9928b0
--- /dev/null
+++ b/lib/gitlab/background_migration/backfill_ci_project_mirrors.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module BackgroundMigration
+    # A job to create ci_project_mirrors entries in batches
+    class BackfillCiProjectMirrors
+      class Project < ActiveRecord::Base # rubocop:disable Style/Documentation
+        include ::EachBatch
+
+        self.table_name = 'projects'
+
+        scope :base_query, -> do
+          select(:id, :namespace_id)
+        end
+      end
+
+      PAUSE_SECONDS = 0.1
+      SUB_BATCH_SIZE = 500
+
+      def perform(start_id, end_id)
+        batch_query = Project.base_query.where(id: start_id..end_id)
+        batch_query.each_batch(of: SUB_BATCH_SIZE) do |sub_batch|
+          first, last = sub_batch.pluck(Arel.sql('MIN(id), MAX(id)')).first
+          ranged_query = Project.unscoped.base_query.where(id: first..last)
+
+          update_sql = <<~SQL
+            INSERT INTO ci_project_mirrors (project_id, namespace_id)
+            #{insert_values(ranged_query)}
+            ON CONFLICT (project_id) DO NOTHING
+          SQL
+          # We do nothing on conflict because we consider they were already filled.
+
+          Project.connection.execute(update_sql)
+
+          sleep PAUSE_SECONDS
+        end
+
+        mark_job_as_succeeded(start_id, end_id)
+      end
+
+      private
+
+      def insert_values(batch)
+        batch.allow_cross_joins_across_databases(url: 'https://gitlab.com/gitlab-org/gitlab/-/issues/336433').to_sql
+      end
+
+      def mark_job_as_succeeded(*arguments)
+        Gitlab::Database::BackgroundMigrationJob.mark_all_as_succeeded('BackfillCiProjectMirrors', arguments)
+      end
+    end
+  end
+end