1 files changed, 19 insertions, 24 deletions

diff --git a/app/models/concerns/relative_positioning.rb b/app/models/concerns/relative_positioning.rb
index 3cbc174536c..7f559f0a7ed 100644
--- a/app/models/concerns/relative_positioning.rb
+++ b/app/models/concerns/relative_positioning.rb
@@ -102,33 +102,16 @@ module RelativePositioning
       delta = at_end ? gap : -gap
       indexed = (at_end ? objects : objects.reverse).each_with_index
 
-      # Some classes are polymorphic, and not all siblings are in the same table.
-      by_model = indexed.group_by { |pair| pair.first.class }
       lower_bound, upper_bound = at_end ? [position, MAX_POSITION] : [MIN_POSITION, position]
 
-      by_model.each do |model, pairs|
-        model.transaction do
-          pairs.each_slice(100) do |batch|
-            # These are known to be integers, one from the DB, and the other
-            # calculated by us, and thus safe to interpolate
-            values = batch.map do |obj, i|
-              desired_pos = position + delta * (i + 1)
-              pos = desired_pos.clamp(lower_bound, upper_bound)
-              obj.relative_position = pos
-              "(#{obj.id}, #{pos})"
-            end.join(', ')
-
-            model.connection.exec_query(<<~SQL, "UPDATE #{model.table_name} positions")
-              WITH cte(cte_id, new_pos) AS (
-               SELECT *
-               FROM (VALUES #{values}) as t (id, pos)
-              )
-              UPDATE #{model.table_name}
-              SET relative_position = cte.new_pos
-              FROM cte
-              WHERE cte_id = id
-            SQL
+      representative.model_class.transaction do
+        indexed.each_slice(100) do |batch|
+          mapping = batch.to_h.transform_values! do |i|
+            desired_pos = position + delta * (i + 1)
+            { relative_position: desired_pos.clamp(lower_bound, upper_bound) }
           end
+
+          ::Gitlab::Database::BulkUpdate.execute([:relative_position], mapping, &:model_class)
         end
       end
 
@@ -200,4 +183,16 @@ module RelativePositioning
   # Override if you want to be notified of failures to move
   def could_not_move(exception)
   end
+
+  # Override if the implementing class is not a simple application record, for
+  # example if the record is loaded from a union.
+  def reset_relative_position
+    reset.relative_position
+  end
+
+  # Override if the model class needs a more complicated computation (e.g. the
+  # object is a member of a union).
+  def model_class
+    self.class
+  end
 end