Fix project destruction failing due to idle in transaction timeoutssh-batch-dependent-destroys

When deleting associated records, Rails loads all associations into memory
(https://github.com/rails/rails/issues/22510) before destroying them. This
can cause a surge in memory and cause destruction of objects to fail
due to idle in transaction database timeouts. This fix is inspired from
https://github.com/thisismydesign to destroy `has_many` relationships
in batches.

Closes #44610

1 files changed, 60 insertions, 0 deletions

diff --git a/spec/models/concerns/batch_destroy_dependent_associations_spec.rb b/spec/models/concerns/batch_destroy_dependent_associations_spec.rb
new file mode 100644
index 00000000000..c16b245bea8
--- /dev/null
+++ b/spec/models/concerns/batch_destroy_dependent_associations_spec.rb
@@ -0,0 +1,60 @@
+require 'spec_helper'
+
+describe BatchDestroyDependentAssociations do
+  class TestProject < ActiveRecord::Base
+    self.table_name = 'projects'
+
+    has_many :builds, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+    has_many :notification_settings, as: :source, dependent: :delete_all # rubocop:disable Cop/ActiveRecordDependent
+    has_many :pages_domains
+    has_many :todos
+
+    include BatchDestroyDependentAssociations
+  end
+
+  describe '#dependent_associations_to_destroy' do
+    set(:project) { TestProject.new }
+
+    it 'returns the right associations' do
+      expect(project.dependent_associations_to_destroy.map(&:name)).to match_array([:builds])
+    end
+  end
+
+  describe '#destroy_dependent_associations_in_batches' do
+    set(:project) { create(:project) }
+    set(:build) { create(:ci_build, project: project) }
+    set(:notification_setting) { create(:notification_setting, project: project) }
+    let!(:todos) { create(:todo, project: project) }
+
+    it 'destroys multiple builds' do
+      create(:ci_build, project: project)
+
+      expect(Ci::Build.count).to eq(2)
+
+      project.destroy_dependent_associations_in_batches
+
+      expect(Ci::Build.count).to eq(0)
+    end
+
+    it 'destroys builds in batches' do
+      expect(project).to receive_message_chain(:builds, :find_each).and_yield(build)
+      expect(build).to receive(:destroy).and_call_original
+
+      project.destroy_dependent_associations_in_batches
+
+      expect(Ci::Build.count).to eq(0)
+      expect(Todo.count).to eq(1)
+      expect(User.count).to be > 0
+      expect(NotificationSetting.count).to eq(User.count)
+    end
+
+    it 'excludes associations' do
+      project.destroy_dependent_associations_in_batches(exclude: [:builds])
+
+      expect(Ci::Build.count).to eq(1)
+      expect(Todo.count).to eq(1)
+      expect(User.count).to be > 0
+      expect(NotificationSetting.count).to eq(User.count)
+    end
+  end
+end