1 files changed, 36 insertions, 0 deletions
diff --git a/lib/gitlab/background_migration/populate_topics_non_private_projects_count.rb b/lib/gitlab/background_migration/populate_topics_non_private_projects_count.rb
new file mode 100644
index 00000000000..1f2b55004e4
--- /dev/null
+++ b/lib/gitlab/background_migration/populate_topics_non_private_projects_count.rb
@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module BackgroundMigration
+    # The class to populates the non private projects counter of topics
+    class PopulateTopicsNonPrivateProjectsCount
+      SUB_BATCH_SIZE = 100
+
+      # Temporary AR model for topics
+      class Topic < ActiveRecord::Base
+        include EachBatch
+
+        self.table_name = 'topics'
+      end
+
+      def perform(start_id, stop_id)
+        Topic.where(id: start_id..stop_id).each_batch(of: SUB_BATCH_SIZE) do |batch|
+          ApplicationRecord.connection.execute(<<~SQL)
+            WITH batched_relation AS #{Gitlab::Database::AsWithMaterialized.materialized_if_supported} (#{batch.select(:id).limit(SUB_BATCH_SIZE).to_sql})
+            UPDATE topics
+            SET non_private_projects_count = (
+              SELECT COUNT(*) 
+              FROM project_topics 
+              INNER JOIN projects 
+              ON project_topics.project_id = projects.id 
+              WHERE project_topics.topic_id = batched_relation.id 
+              AND projects.visibility_level > 0
+            )
+            FROM batched_relation
+            WHERE topics.id = batched_relation.id
+          SQL
+        end
+      end
+    end
+  end
+end