Loaded associations should not run a new query when size is called #32617

tgturner · 2018-04-18T02:15:06Z

Already loaded associations were running an extra query when size was called on the association.
This fix ensures that an extra query is no longer run.

This addresses #32569

rails-bot · 2018-04-18T02:15:09Z

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chancancode · 2018-04-21T05:26:49Z

activerecord/lib/active_record/associations/collection_association.rb

@@ -231,7 +233,7 @@ def size
      # loaded and you are going to fetch the records anyway it is better to
      # check <tt>collection.length.zero?</tt>.
      def empty?
-        if loaded?
+        if loaded? || @association_ids


We talked about this briefly in the issue and think this should probably have the !find_target? check as well. Can you investigate why that may matter, and if it does, add a test for it?

I think we don't need the !find_target? since that will be implicit if @association_ids is defined because it calls size.zero?.

chancancode · 2018-04-21T05:26:49Z

activerecord/test/cases/associations/has_many_associations_test.rb

+      car.bulbs.size
+    end
+  end
+


Can you add tests for empty? as well?

kamipo · 2018-04-21T07:24:06Z

activerecord/lib/active_record/associations/collection_association.rb

@@ -212,6 +212,8 @@ def destroy(*records)
      def size
        if !find_target? || loaded?
          target.size
+        elsif @association_ids
+          @association_ids.length


Can you rebase on current master?
This branch will break existing behavior described at e76e477 since ids_reader doesn't respect dirty target when the target is not loaded yet.

tgturner · 2018-04-21T15:54:29Z

@chancancode I don't think the !find_target check in empty? is necessary. I added all relevant test cases I could think of.

Thanks to @kamipo, I noticed that the changes I made were causing incorrect results to be returned for models with unsaved associations. Handling that case, I believe, handled the need for !find_target. Please let me know if any of my assumptions are incorrect, and thanks for working on this with me!

chancancode · 2018-04-24T16:03:07Z

This seems good to me but I would love if @pixeltrix or @kamipo can double check the more subtle aspects of this as I am not super familiar with them, so I might have missed some things.

tgturner · 2018-04-24T20:40:05Z

Thanks for following up!

kamipo · 2018-04-26T14:08:18Z

activerecord/CHANGELOG.md

@@ -1,3 +1,8 @@
+*   Ensure `Associations::CollectionAssociation#size` and `Associations::CollectionAssociation#empty`


s/empty/empty?/

kamipo · 2018-04-26T14:08:18Z

activerecord/lib/active_record/associations/collection_association.rb

@@ -212,6 +212,8 @@ def destroy(*records)
      def size
        if !find_target? || loaded?
          target.size
+        elsif @association_ids && target.empty?
+          @association_ids.length


I prefer @association_ids.size since it is an only place using length in the class.

kamipo · 2018-04-26T14:08:18Z

activerecord/test/cases/associations/has_many_associations_test.rb

+  def test_collection_empty_with_dirty_target
+    post = posts(:thinking)
+    assert_equal [], post.reader_ids
+    assert_equal true, post.readers.empty?


assert_empty post.readers

kamipo · 2018-04-26T14:08:18Z

activerecord/test/cases/associations/has_many_associations_test.rb

+    post.readers.reset
+    post.readers.build
+    assert_equal [], post.reader_ids
+    assert_equal false, post.readers.empty?


assert_not_empty post.readers

kamipo · 2018-04-26T14:08:18Z

activerecord/test/cases/associations/has_many_associations_test.rb

+    car_two = Car.create!
+    car_two.bulb_ids
+
+    assert_queries(0) do


assert_no_queries do

kamipo · 2018-04-26T14:08:18Z

activerecord/test/cases/associations/has_many_associations_test.rb

+      assert_equal false, car.bulbs.empty?
+    end
+
+    assert_queries(0) do


assert_no_queries do

kamipo · 2018-04-26T14:08:18Z

activerecord/test/cases/associations/has_many_associations_test.rb

+    car_two = Car.create!
+
+    assert_queries(1) do
+      assert_equal false, car.bulbs.empty?


assert_not_empty car.bulbs

kamipo · 2018-04-26T14:08:18Z

activerecord/test/cases/associations/has_many_associations_test.rb

+    end
+
+    assert_queries(1) do
+      assert_equal true, car_two.bulbs.empty?


assert_empty car_two.bulbs

kamipo · 2018-04-26T14:08:18Z

activerecord/test/cases/associations/has_many_associations_test.rb

+    car_two.bulb_ids
+
+    assert_queries(0) do
+      assert_equal false, car.bulbs.empty?


assert_not_empty car.bulbs

kamipo · 2018-04-26T14:08:18Z

activerecord/test/cases/associations/has_many_associations_test.rb

+    end
+
+    assert_queries(0) do
+      assert_equal true, car_two.bulbs.empty?


assert_empty car_two.bulbs

tgturner · 2018-04-26T15:51:25Z

@kamipo Thank you for the feedback! Updated PR based on your comments and rebased on top of Master

kamipo

Looks good to me. Can you squash your commits into one?

Already loaded associations were running an extra query when `size` was called on the association. This fix ensures that an extra query is no longer run. Update tests to use proper methods

tgturner · 2018-04-26T16:42:09Z

Done!

chancancode · 2018-04-27T21:10:45Z

Thank you @tgturner and everyone else who reviewed the PR! ❤️

tgturner · 2018-04-27T21:19:59Z

Thanks to everyone that helped!

rails-bot assigned kaspth Apr 18, 2018

chancancode reviewed Apr 21, 2018

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kamipo reviewed Apr 21, 2018

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tgturner force-pushed the size-should-use-available-association branch from 876a6ff to 45f566d Compare April 21, 2018 15:48

chancancode assigned pixeltrix and kamipo and unassigned kaspth Apr 24, 2018

kamipo reviewed Apr 26, 2018

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tgturner force-pushed the size-should-use-available-association branch from 45f566d to d061eb4 Compare April 26, 2018 15:50

kamipo approved these changes Apr 26, 2018

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Loaded associations should not run a new query when size is called

b07b970

Already loaded associations were running an extra query when `size` was called on the association. This fix ensures that an extra query is no longer run. Update tests to use proper methods

tgturner force-pushed the size-should-use-available-association branch from d061eb4 to b07b970 Compare April 26, 2018 16:41

kamipo merged commit 0a8fe15 into rails:master Apr 27, 2018

chancancode mentioned this pull request Apr 27, 2018

CollectionAssociation#size should use @association_ids if available #32569

Closed

tgturner deleted the size-should-use-available-association branch April 27, 2018 21:20

Loaded associations should not run a new query when size is called #32617

Loaded associations should not run a new query when size is called #32617

tgturner commented Apr 18, 2018

rails-bot commented Apr 18, 2018

chancancode Apr 21, 2018

pixeltrix Apr 25, 2018

chancancode Apr 21, 2018

kamipo Apr 21, 2018

tgturner commented Apr 21, 2018

chancancode commented Apr 24, 2018

tgturner commented Apr 24, 2018

kamipo Apr 26, 2018

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tgturner commented Apr 26, 2018

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tgturner commented Apr 26, 2018

chancancode commented Apr 27, 2018

tgturner commented Apr 27, 2018

		@@ -1,3 +1,8 @@
		* Ensure `Associations::CollectionAssociation#size` and `Associations::CollectionAssociation#empty`

Loaded associations should not run a new query when size is called #32617

Loaded associations should not run a new query when size is called #32617

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tgturner commented Apr 26, 2018

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