N+1 problem happen with using Time.current in where sentence(maybe)

[gento-ogane]

environment

• Ruby: ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [aarch64-linux]
• Rails: 7.0.4
• graphql 1.13.12
• graphql-batch 0.4.3
• graphql-pro 1.22.2

I'm creating Rails app with following modules;

Steps to reproduce

module Loaders
  class CountLoader < GraphQL::Batch::Loader
    def initialize(model, column: model.primary_key, conditions: {})
      super()
      @model = model
      @column = column
      @joins = conditions[:joins]
      @wheres = conditions[:wheres]
      @where_nots = conditions[:where_nots]
      @distinct = conditions[:distinct] || false
    end

    def perform(keys)
      query(keys).each { |key, count| fulfill(key, count) }
      keys.each { |key| fulfill(key, 0) unless fulfilled?(key) }
    end

    private

    def query(keys)
      scope = @model
      scope = scope.joins(@joins) if @joins.present?
      @wheres.each { |w| scope = scope.where(w) } if @wheres.present?
      @where_nots.each { |w| scope = scope.where.not(w) } if @where_nots.present?

      if @distinct
        scope.where(@column => keys).group(@column).distinct.count
      else
        scope.where(@column => keys).group(@column).count
      end
    end
  end
end

module Types
  class User < Types::SchemaObject
    def suggested_similar_property_other_client_count(property_id:)
      end_time = Time.current
      start_time = end_time.ago(30.days).beginning_of_day

      wheres = [
          {
            messages:
            {
              created_at: start_time..end_time,
            },
          },
        ]
      joins = [:messages]
      conditions = { joins:, wheres:, distinct: true }

      Loaders::CountLoader.for(
        ::Chat::Room,
        column: :user_id,
        conditions:,
      ).load(object.id)
    end
  end
end

class User < ApplicationRecord
...
has_many :chat_rooms, class_name: 'Chat::Room'
...
end

class Chat::Room < ApplicationRecord
...
belongs_to :user
has_many :messages
...
end

actual result

graphql-batch generates this SQL;

SELECT COUNT(DISTINCT `chat_rooms`.`id`) AS `count_id`, `chat_rooms`.`user_id` AS `chat_rooms_user_id` FROM `chat_rooms` INNER JOIN `chat_
messages` `messages` ON `messages`.`room_id` = `chat_rooms`.`id` WHERE `messages`.`created_at` BETWEEN '2023-05-16 00:00:00' AND '2023-06-15 18:51:49' AND `chat_rooms`.`user_id` = 136 GROUP BY `chat_rooms`.`user_id`

SELECT COUNT(DISTINCT `chat_rooms`.`id`) AS `count_id`, `chat_rooms`.`user_id` AS `chat_rooms_user_id` FROM `chat_rooms` INNER JOIN `chat_m
essages` `messages` ON `messages`.`room_id` = `chat_rooms`.`id` WHERE `messages`.`created_at` BETWEEN '2023-05-16 00:00:00' AND '2023-06-15 18:51:49' AND `chat_rooms`.`user_id` = 137 GROUP BY `chat_rooms`.`user_id`

expected result

graphql-batch should generate;

SELECT COUNT(DISTINCT `chat_rooms`.`id`) AS `count_id`, `chat_rooms`.`user_id` AS `chat_rooms_user_id` FROM `chat_rooms` INNER JOIN `chat_
messages` `messages` ON `messages`.`room_id` = `chat_rooms`.`id` WHERE `messages`.`created_at` BETWEEN '2023-05-16 00:00:00' AND '2023-06-15 18:51:49' AND `chat_rooms`.`user_id` IN (136, 137) GROUP BY `chat_rooms`.`user_id`

additional information

In my case, this problem is resolved with following code.

 def suggested_similar_property_other_client_count(property_id:)
  end_time = Time.zone.today ## !<= changed!
  start_time = end_time.ago(30.days).beginning_of_day

  wheres = [
      {
        messages:
        {
          created_at: start_time..end_time,
        },
      },
    ]
  joins = [:messages]
  conditions = { joins:, wheres:, distinct: true }

  Loaders::CountLoader.for(
    ::Chat::Room,
    column: :user_id,
    conditions:,
  ).load(object.id)
 end

[swalkinshaw]

This is how graphql-batch works and shouldn't be considered a bug. Since you're passing in a timestamp to for, that becomes part of the batch loader "grouping" cache key. Time.current including seconds (and microseconds) so every call will have a different value of course.

Time.zone.today gets around that since the value will be the same within each day at least.

[gento-ogane]

I now have a deeper understanding of this good gem.
Thank you!