GraphQL Ruby N+1 批处理问题答案

【问题标题】：GraphQL Ruby N+1 Batching IssueGraphQL Ruby N+1 批处理问题
【发布时间】：2018-10-08 13:24:07
【问题描述】：

我在 Ruby 中使用带有 Batch 和 QueryResolver gem 的 GraphQL。除了这个问题，他们工作得很好，似乎无法弄清楚为什么会发生这种情况。它似乎正在加载“所有关系”，然后在不久之后加载“第一：X”关系。这导致数百个 ID 被传递到 SELECT * ... IN (...) 查询中，而不是先做 hte: X 在 IN () 查询中。这是我的查询：

query getCenterPayments(
  $centerId: ID!
  $first: Int
) {
  viewer {
    id
    centers(id: $centerId) {
      edges {
        node {
          id
          currency
          payments(
            first: $first
          ) {
            pageInfo {
              hasNextPage
              hasPreviousPage
              endCursor
              startCursor
            }
            edges {
              cursor
              node {
                id
                participant { <---- N+1 Queries here
                  id
                  name
                }
              }
            }
          }
        }
      }
    }
  }
}

这是在后台执行的查询...

User Load (0.4ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT $2[["id", 1], ["LIMIT", 1]]
  Center Load (1.4ms)  SELECT "centers".* FROM "centers" INNER JOIN "members" ON "centers"."id" = "members"."center_id" WHERE "members"."user_id" = $1 AND (centers.uid = 'xxxxx' OR centers.slug = 'xxxxx')  [["user_id", 1]]
  Payment Load (15.5ms)  SELECT "payments".* FROM "payments" WHERE "payments"."center_id" = 1
  User Load (7.0ms)  SELECT "users".* FROM "users" WHERE "users"."id" IN (2, 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49,50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92,93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145,146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231,232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283, 284, 285, 286, 287, 288, 289, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311, 312, 313, 314, 315, 316, 317,318, 319, 320, 321, 322, 323, 324, 325, 326, 327, 328, 329, 330, 331, 332, 333, 334, 335, 336, 337, 338, 339, 340, 341, 342, 343, 344, 345, 346, 347, 348, 349, 350, 351, 352, 353, 354, 355, 356, 357, 358, 359, 360, 361, 362, 363, 364, 365, 366, 367, 368, 369, 370, 371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 382, 383, 384, 385, 386, 387, 388, 389, 390, 391, 392, 393, 394, 395, 396, 397, 398, 399, 400, 401, 402, 403,404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 416, 417, 418, 419, 420, 421, 422, 423, 424, 425, 426, 427, 428, 429, 430, 431, 432, 433, 434, 435, 436, 437, 438, 439, 440, 441, 442, 443, 444, 445, 446, 447, 448, 449, 450, 451, 452, 453, 454, 455, 456, 457, 458, 459, 460, 461, 462, 463, 464, 465, 466, 467, 468, 469, 470, 471, 472, 473, 474, 475, 476, 477, 478, 479, 480, 481, 482, 483, 484, 485, 486, 487, 488, 489,490, 491, 492, 493, 494, 495, 496, 497, 498, 499, 500, 501, 502, 503, 504, 505, 506, 507)
  Member Exists (0.7ms)  SELECT  1 AS one FROM "members" WHERE "members"."center_id" = $1 AND "members"."discarded_at" IS NULL AND "members"."role" = $2 AND "members"."user_id" = $3 LIMIT $4  [["center_id", 1], ["role", "admin"], ["user_id", 1], ["LIMIT", 1]]
  Payment Load (13.9ms)  SELECT "payments".* FROM "payments" WHERE "payments"."center_id" = $1 ORDER BY "payments"."date" DESC  [["center_id", 1]]
  User Load (7.1ms)  SELECT "users".* FROM "users" WHERE "users"."id" IN (237, 149, 298, 506, 278, 497, 76, 138, 139, 4, 61, 274, 449, 450, 243, 311, 93, 239, 496, 307, 78, 59, 453, 499, 500, 490, 489, 447, 337, 437, 300, 255, 187, 186, 446, 387, 401, 371, 481, 502, 390, 340, 341, 504, 505, 494, 151, 7, 465, 393, 174, 419, 103, 487, 503, 454, 498, 417, 418, 495, 472, 58, 442, 501, 263, 275, 285, 476, 486, 140, 116, 479, 493, 488, 178, 507, 226, 229, 372, 373, 134, 133, 228, 483, 484, 114, 431, 258, 463, 468, 462, 441, 68, 459, 460, 438, 403, 404, 148, 242, 204, 439, 46, 70, 127, 429, 492, 350, 317, 366, 491, 358, 360, 150, 84, 407, 455, 456, 164, 363, 365, 413, 155, 402, 485, 238, 482, 314, 315, 142, 221, 480, 478, 383, 389, 470, 85, 458, 477, 445, 467, 466, 250,251, 412, 411, 165, 475, 432, 461, 474, 216, 361, 334, 473, 436, 451, 427, 471, 464, 272, 271, 422, 302, 95, 94, 469, 400, 380, 231, 434, 448, 378, 457, 67, 382, 381, 430,6, 452, 206, 428, 220, 367, 368, 444, 167, 408, 443, 130, 426, 109, 440, 224, 410, 24, 421, 435, 312, 313, 433, 384, 335, 283, 423, 424, 357, 392, 141, 425, 388, 30, 420, 168, 266, 321, 336, 416, 415, 414, 377, 399, 406, 83, 288, 292, 409, 405, 398, 396, 351, 359, 297, 397, 395, 394, 391, 214, 105, 364, 369, 386, 370, 333, 379, 296, 40, 385,352, 189, 346, 342, 375, 376, 332, 353, 374, 338, 323, 356, 354, 236, 362, 355, 347, 185, 326, 325, 324, 179, 348, 349, 219, 166, 249, 193, 345, 322, 343, 344, 111, 316, 299, 339, 331, 203, 276, 31, 293, 304, 329, 112, 113, 328, 327, 330, 319, 241, 240, 91,308, 309, 270, 310, 320, 55, 318, 210, 306, 200, 102, 247, 248, 235, 173, 305, 232, 264, 201, 202, 154, 217, 294, 265, 252, 303, 12, 213, 147, 301, 282, 286, 287, 291, 295, 290, 279, 289, 284, 38, 225, 227, 106, 245, 280, 19, 281, 244, 277, 159, 273, 268, 77, 269, 51, 246, 234, 230, 65, 66, 260, 56, 267, 262, 223, 261, 146, 259, 254, 253, 190, 257, 256, 181, 74, 162, 97, 175, 121, 233, 171, 194, 16, 188, 163, 222, 60, 41, 212, 208, 215, 218, 137, 26, 207, 209, 176, 211, 195, 131, 132, 144, 136, 196, 197, 199, 143, 129, 180, 184, 71, 156, 183, 128, 34, 191, 192, 205, 11, 198, 182, 152, 82, 29, 172, 27, 28, 170, 169, 177, 101, 99, 145, 17, 160, 48, 49, 124, 100, 161, 108, 107, 122, 157, 158, 123, 115, 110, 125, 8, 153, 57, 135, 44, 9, 119, 126, 3, 10, 13, 22, 75, 104, 118, 21, 120, 2, 117, 15, 50, 25, 90, 80, 96, 36, 47, 89, 87, 98, 23, 86, 92, 81, 88, 53, 63, 64, 37, 14, 73, 72, 18, 20, 32, 45, 39, 79, 42, 43, 62, 54, 33, 69, 52, 35, 5)
  Payment Load (0.6ms)  SELECT  "payments".* FROM "payments" WHERE "payments"."center_id" = $1 ORDER BY "payments"."date" DESC LIMIT $2  [["center_id", 1], ["LIMIT", 10]]
   (2.0ms)  SELECT COUNT(*) FROM "payments" WHERE "payments"."center_id" = $1  [["center_id", 1]]
  Center Load (0.5ms)  SELECT "centers".* FROM "centers" WHERE "centers"."id" = 1
  User Load (1.0ms)  SELECT "users".* FROM "users" WHERE "users"."id" IN (237, 149, 298, 506, 278, 497, 76, 138, 139, 4)
Completed 200 OK in 680ms (Views: 1.6ms | ActiveRecord: 50.3ms)

正如你所见，它加载了很多不必要的用户，尽管我是为用户的解析器这样做的：

field :participant do
  type UserType

  resolve -> (obj, args, ctx) {
    RecordLoader.for(User).load(obj.participant_id)
  }
end

你以前也遇到过这种情况吗？

【问题讨论】：

使用bullet gem github.com/flyerhzm/bullet 找出（N + 1）个查询。
也许您需要对关联记录执行includes？我还没有将 GraphQL 与 Rails 一起使用（嫉妒！），但也许 Rails 和 GraphQL 相处得并不好。 Bullet 在这里可能也有助于诊断。
@emptywalls 是的，如果我正在执行 REST 类型的 API，那会起作用，但 GQL 设置会产生过度杀伤力，特别是如果我不想要这些字段。大量多余的数据。
@emptywalls 是的，rails 对于 gql 来说非常棒。到目前为止，这可能是我对中小型项目的选择。 :D

标签： ruby-on-rails ruby graphql graphql-ruby

【解决方案1】：

您可以使用 graphql-preload gem 在 Graphql 中预加载关联

https://github.com/ConsultingMD/graphql-preload

field :payment do
    preload :participants
    resolve -> (obj, args, ctx) {
      obj.participants
    }
end

【讨论】：

【解决方案2】：

问题在于同时使用两个解析器。看起来 QueryResolver 在限制之前解析，因为下一个查询解析器正在寻求解决其查询。它正在造成混乱。我最终选择了 Shopify 的 Batch gem，并且对它非常满意。

【讨论】：