1 files changed, 29 insertions, 0 deletions
diff --git a/lib/gitlab/background_migration/reset_duplicate_ci_runners_token_values.rb b/lib/gitlab/background_migration/reset_duplicate_ci_runners_token_values.rb
new file mode 100644
index 00000000000..cfd6a4e4091
--- /dev/null
+++ b/lib/gitlab/background_migration/reset_duplicate_ci_runners_token_values.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module BackgroundMigration
+    # A job to nullify duplicate token values in ci_runners table in batches
+    class ResetDuplicateCiRunnersTokenValues < BatchedMigrationJob
+      def perform
+        each_sub_batch(operation_name: :nullify_duplicate_ci_runner_token_values) do |sub_batch|
+          # Reset duplicate runner tokens that would prevent creating an unique index.
+          nullify_duplicate_ci_runner_token_values(sub_batch)
+        end
+      end
+
+      private
+
+      def nullify_duplicate_ci_runner_token_values(sub_batch)
+        batchable_model = define_batchable_model(batch_table, connection: connection)
+
+        duplicate_tokens = batchable_model
+                             .where(token: sub_batch.select(:token).distinct)
+                             .group(:token)
+                             .having('COUNT(*) > 1')
+                             .pluck(:token)
+
+        batchable_model.where(token: duplicate_tokens).update_all(token: nil) if duplicate_tokens.any?
+      end
+    end
+  end
+end