1 files changed, 26 insertions, 0 deletions
diff --git a/config/initializers/active_record_keyset_pagination.rb b/config/initializers/active_record_keyset_pagination.rb
index f5692c95276..7f830cafd31 100644
--- a/config/initializers/active_record_keyset_pagination.rb
+++ b/config/initializers/active_record_keyset_pagination.rb
@@ -1,10 +1,36 @@
 # frozen_string_literal: true
 
 module PaginatorExtension
+  KEYSET_ORDER_PLACEHOLDER = Object.new
+
   # This method loads the records for the requested page and returns a keyset paginator object.
   def keyset_paginate(cursor: nil, per_page: 20, keyset_order_options: {})
     Gitlab::Pagination::Keyset::Paginator.new(scope: self.dup, cursor: cursor, per_page: per_page, keyset_order_options: keyset_order_options)
   end
+
+  # This modifies `reverse_sql_order` so that it is aware of Gitlab::Pagination::Keyset::Order which
+  # can reverse order clauses with NULLS LAST because we provide it a `reversed_order_expression`.
+  # This allows us to use `#last` on these relations.
+  #
+  # Overrides https://github.com/rails/rails/blob/v6.1.6.1/activerecord/lib/active_record/relation/query_methods.rb#L1331-L1358
+  def reverse_sql_order(order_query)
+    return super if order_query.empty?
+
+    keyset_order_values = []
+
+    order_query_without_keyset = order_query.flat_map do |o|
+      next o unless o.is_a?(Gitlab::Pagination::Keyset::Order)
+
+      keyset_order_values << o
+      KEYSET_ORDER_PLACEHOLDER
+    end
+
+    super(order_query_without_keyset).map do |o|
+      next o unless o == KEYSET_ORDER_PLACEHOLDER
+
+      keyset_order_values.shift.reversed_order
+    end
+  end
 end
 
 ActiveSupport.on_load(:active_record) do