1 files changed, 63 insertions, 0 deletions
diff --git a/lib/gitlab/background_migration/extract_project_topics_into_separate_table.rb b/lib/gitlab/background_migration/extract_project_topics_into_separate_table.rb
new file mode 100644
index 00000000000..31b5b5cdb73
--- /dev/null
+++ b/lib/gitlab/background_migration/extract_project_topics_into_separate_table.rb
@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module BackgroundMigration
+    # The class to extract the project topics into a separate `topics` table
+    class ExtractProjectTopicsIntoSeparateTable
+      # Temporary AR table for tags
+      class Tag < ActiveRecord::Base
+        self.table_name = 'tags'
+      end
+
+      # Temporary AR table for taggings
+      class Tagging < ActiveRecord::Base
+        self.table_name = 'taggings'
+        belongs_to :tag
+      end
+
+      # Temporary AR table for topics
+      class Topic < ActiveRecord::Base
+        self.table_name = 'topics'
+      end
+
+      # Temporary AR table for project topics
+      class ProjectTopic < ActiveRecord::Base
+        self.table_name = 'project_topics'
+        belongs_to :topic
+      end
+
+      # Temporary AR table for projects
+      class Project < ActiveRecord::Base
+        self.table_name = 'projects'
+      end
+
+      def perform(start_id, stop_id)
+        Tagging.includes(:tag).where(taggable_type: 'Project', id: start_id..stop_id).each do |tagging|
+          if Project.exists?(id: tagging.taggable_id) && tagging.tag
+            begin
+              topic = Topic.find_or_create_by(name: tagging.tag.name)
+              project_topic = ProjectTopic.find_or_create_by(project_id: tagging.taggable_id, topic: topic)
+
+              tagging.delete if project_topic.persisted?
+            rescue StandardError => e
+              Gitlab::ErrorTracking.log_exception(e, tagging_id: tagging.id)
+            end
+          else
+            tagging.delete
+          end
+        end
+
+        mark_job_as_succeeded(start_id, stop_id)
+      end
+
+      private
+
+      def mark_job_as_succeeded(*arguments)
+        Gitlab::Database::BackgroundMigrationJob.mark_all_as_succeeded(
+          self.class.name.demodulize,
+          arguments
+        )
+      end
+    end
+  end
+end