使用 SELECT MAX 的集合的 ActiveRecord 查询在 Rails 中表现不佳

Question

我有3个主要模型，可能有数千个组件和测试记录。

class Component
  has_many :test_records, as: :testable
end

class TestRecord
  belongs_to :testable, polymorphic: true
  belongs_to :test_form
end

class TestForm
  has_many :test_records
end

测试记录是在测试可测试项目后生成的，它们导致通过或失败存储为布尔值

test_record.passed

我想做的是提取每个组件的最新测试记录并确定它是否通过。我首先检查它是否已经过以下范围的测试：

  scope :tested, ->(test_form_id) { 
    where("test_records.created_at > ?", 45.days.ago)
    .order(created_at: :desc)
    .distinct
    .joins(:test_records)
    .where("test_records.test_form_id = ?", test_form_id)
    .active
  }

然后我将它传递给：

  scope :passed, ->(test_form_id, type) {
    tested(test_form_id)
    .includes(:test_records)
    .where('test_records.test_form_id = ?', test_form_id)
    .where("test_records.created_at = (
     SELECT MAX(test_records.created_at) 
     FROM test_records 
     WHERE test_records.testable_id = #{type}.id)")
    .where("tested_records.passed = none")
   }

此查询在生产环境中运行需要 20 秒。

我试过以下方法：

scope :passed, ->(test_form_id, type) {
      tested(test_form_id)
      .distinct('ON (test_records.testable_id)')
      .order('test_records.created_at DESC')
      .where('test_records.test_form_id = ?', test_form_id)
      .where('test_records.passed = ?', true)
      .includes(:test_records)
  }

但它没有给出正确的结果，因为它在 distinct 调用之前过滤掉了一个 passed == false 测试记录。

TLDR：我有经过测试的组件，我想 select 为特定 test_form 创建的最后一个 test_record if test_record.passed == true ;目前查询所花的时间比我想要的长 40 倍，如果能帮助我清理活动记录查询，我将不胜感激

谢谢！

编辑：这是 PG EXPLAIN ANALYZE 结果：

    Unique  (cost=1155.71..1155.76 rows=1 width=150) (actual time=8504.313..8504.326 rows=2 loops=1)
   ->  Sort  (cost=1155.71..1155.72 rows=1 width=150) (actual time=8504.312..8504.317 rows=2 loops=1)
         Sort Key: components.created_at DESC, components.id, components.barcode, components.description, components.make, components.model, components.system_id, components.updated_at, components.active, components.component_type, components.abbreviation, components.address, test_records.id, test_records.user_id, test_records.passed, test_records.created_at, test_records.updated_at, test_records.manufacturer_test_form_id
         Sort Method: quicksort  Memory: 25kB
         ->  Hash Join  (cost=798.86..1155.70 rows=1 width=150) (actual time=8502.399..8504.226 rows=2 loops=1)
               Hash Cond: ((test_records.testable_id = components.id) AND (test_records.created_at = (SubPlan 1)))
               ->  Hash Join  (cost=42.09..243.44 rows=9 width=70) (actual time=1.000..1.010 rows=4 loops=1)
                     Hash Cond: (test_records.testable_id = components_systems.component_id)
                     ->  Bitmap Heap Scan on test_records  (cost=19.85..218.41 rows=718 width=62) (actual time=0.409..0.718 rows=418 loops=1)
                           Recheck Cond: (test_form_id = 14)
                           Filter: (passed AND (created_at > '2020-11-03 02:49:31.234492'::timestamp without time zone) AND ((testable_type)::text = 'Component'::text))
                           Rows Removed by Filter: 1106
                           Heap Blocks: exact=92
                           ->  Bitmap Index Scan on index_test_records_on_test_form_id  (cost=0.00..19.67 rows=1518 width=0) (actual time=0.072..0.073 rows=1525 loops=1)
                                 Index Cond: (test_form_id = 14)
                     ->  Hash  (cost=16.43..16.43 rows=465 width=8) (actual time=0.214..0.215 rows=478 loops=1)
                           Buckets: 1024  Batches: 1  Memory Usage: 27kB
                           ->  Index Only Scan using index_components_systems_on_system_id_and_component_id on components_systems  (cost=0.29..16.43 rows=465 width=8) (actual time=0.039..0.119 rows=478 loops=1)
                                 Index Cond: (system_id = 2747)
                                 Heap Fetches: 0
               ->  Hash  (cost=704.23..704.23 rows=3503 width=88) (actual time=8499.537..8499.538 rows=1509 loops=1)
                     Buckets: 4096  Batches: 1  Memory Usage: 246kB
                     ->  Bitmap Heap Scan on components  (cost=43.81..704.23 rows=3503 width=88) (actual time=0.197..3.433 rows=3478 loops=1)
                           Recheck Cond: (component_profile_id = 13)
                           Filter: (active AND active)
                           Rows Removed by Filter: 22
                           Heap Blocks: exact=235
                           ->  Bitmap Index Scan on index_components_on_component_profile_id  (cost=0.00..42.94 rows=3553 width=0) (actual time=0.165..0.165 rows=3695 loops=1)
                                 Index Cond: (component_profile_id = 13)
                     SubPlan 1
                       ->  Aggregate  (cost=345.43..345.44 rows=1 width=8) (actual time=2.440..2.440 rows=1 loops=3480)
                             ->  Seq Scan on test_records test_records_1  (cost=0.00..345.43 rows=1 width=8) (actual time=1.775..2.437 rows=0 loops=3480)
                                   Filter: (testable_id = components.id)
                                   Rows Removed by Filter: 13897
 Planning Time: 0.794 ms
 Execution Time: 8504.505 ms

Answer 1

好吧，解决方案确实比我想象的要简单。我在下面添加了一个迁移：

add_index :test_records, [:testable_id, :testable_type]

之后查询下降到 1.010 毫秒

使用 SELECT MAX 的集合的 ActiveRecord 查询在 Rails 中表现不佳

ActiveRecord Query for a Collection using SELECT MAX exhibiting poor performance in Rails

ruby-on-rails

postgresql

indexing

max

rails-activerecord