Create stable connection for pagination

app/graphql/sagittarius_schema.rb

@@ -7,6 +7,7 @@ class SagittariusSchema < GraphQL::Schema
   query(Types::QueryType)
 
   default_max_page_size 50
+  connections.add(ActiveRecord::Relation, Sagittarius::Graphql::StableConnection)
 
   # For batch-loading (see https://graphql-ruby.org/dataloader/overview.html)
   use GraphQL::Dataloader

lib/sagittarius/graphql/stable_connection.rb

@@ -0,0 +1,68 @@
+# frozen_string_literal: true
+
+module Sagittarius
+  module Graphql
+    # rubocop:disable GraphQL/ObjectDescription -- this is a connection implementation, not a GraphQL object
+    class StableConnection < GraphQL::Pagination::Connection
+      def cursor_for(item)
+        encode(item.id.to_s)
+      end
+
+      def backward?
+        @before_value.present? || @last_value.present?
+      end
+
+      def page_size
+        if backward?
+          [@last_value, max_page_size].compact.min
+        else
+          [@first_value, max_page_size].compact.min
+        end
+      end
+
+      def results
+        @results ||= begin
+          if backward?
+            paginate_backward
+          elsif @after_value.present?
+            paginate_forward
+          end
+
+          @items.limit(page_size + 1)
+        end
+      end
+
+      def paginate_backward
+        before_id = Integer(decode(@before_value), exception: false)
+        if before_id.nil? && !@before_value.nil?
+          raise GraphQL::ExecutionError, "Invalid cursor '#{@before_value}' provided"
+        end
+
+        @items = @items.where('id < ?', before_id) unless before_id.nil?
+        @items = @items.reverse_order
+      end
+
+      def paginate_forward
+        after_id = Integer(decode(@after_value), exception: false)
+        raise GraphQL::ExecutionError, "Invalid cursor '#{@after_value}' provided" if after_id.nil?
+
+        @items = @items.where('id > ?', after_id)
+      end
+
+      def nodes
+        results.slice(0, page_size)
+      end
+
+      # rubocop:disable Naming/PredicateName -- this is required by graphql-ruby
+      def has_next_page
+        !backward? && results.size > page_size
+      end
+
+      def has_previous_page
+        backward? && results.size > page_size
+      end
+      # rubocop:enable Naming/PredicateName
+    end
+    # rubocop:enable GraphQL/ObjectDescription
+  end
+end