Change work_histories migration to insert via SQL

Previously, the data migration
BackfillApplicationChoicesWithWorkExperiences was inserting records via
ActiveRecord. This caused an incident, known as 'The Big Touch'. A lot
of application choices, forms and candidates had their updated_at
updated and this caused some of our APIs to be slow.

We still need to run this migration in sandbox so we thought it's a good
idea to change this migration to insert records via SQL avoiding any
callbacks.

app/workers/migrate_application_choices_worker.rb

@@ -4,36 +4,55 @@ class MigrateApplicationChoicesWorker
   sidekiq_options queue: :low_priority
 
   def perform(choice_ids)
-    errors = []
+    return if HostingEnvironment.production?
 
-    ApplicationChoice.where(id: choice_ids).find_each(batch_size: 100) do |choice|
-      ActiveRecord::Base.transaction do
-        application_form = choice.application_form
+    application_experiences = []
+    work_history_breaks = []
 
-        if choice.work_experiences.blank? && application_form.application_work_experiences.any?
-          choice.work_experiences = application_form.application_work_experiences.map(&:dup)
-        end
+    ApplicationChoice.where(id: choice_ids).find_each(batch_size: 100) do |choice|
+      application_form = choice.application_form
+
+      if choice.work_experiences.blank? && application_form.application_work_experiences.any?
+        application_experiences += valid_attributes(
+          application_form.application_work_experiences.map(&:dup),
+          choice,
+          'experienceable',
+        )
+      end
 
-        if choice.volunteering_experiences.blank? && application_form.application_volunteering_experiences.any?
-          choice.volunteering_experiences = application_form.application_volunteering_experiences.map(&:dup)
-        end
+      if choice.volunteering_experiences.blank? && application_form.application_volunteering_experiences.any?
+        application_experiences += valid_attributes(
+          application_form.application_volunteering_experiences.map(&:dup),
+          choice,
+          'experienceable',
+        )
+      end
 
-        if choice.work_history_breaks.blank? && application_form.application_work_history_breaks.any?
-          choice.work_history_breaks = application_form.application_work_history_breaks.map(&:dup)
-        end
+      if choice.work_history_breaks.blank? && application_form.application_work_history_breaks.any?
+        work_history_breaks += valid_attributes(
+          application_form.application_work_history_breaks.map(&:dup),
+          choice,
+          'breakable',
+        )
       end
-    rescue ActiveRecord::RecordInvalid => e
-      errors << "Error choice id #{choice.id}: #{e.message}"
     end
 
-    if errors
-      errors.each do |error|
-        Rails.logger.info error
-      end
+    ApplicationExperience.insert_all(application_experiences) if application_experiences.any?
+    ApplicationWorkHistoryBreak.insert_all(work_history_breaks) if work_history_breaks.any?
+  end
 
-      Rails.logger.info "#{errors.count} errors"
-    end
+private
 
-    Rails.logger.info 'No errors' if errors.blank?
+  def valid_attributes(records, choice, polymorphic_column)
+    records.map do |record|
+      attributes = record.attributes
+      attributes["#{polymorphic_column}_type"] = 'ApplicationChoice'
+      attributes["#{polymorphic_column}_id"] = choice.id
+      attributes['created_at'] = Time.zone.now
+      attributes['updated_at'] = Time.zone.now
+      attributes.delete('id')
+
+      attributes
+    end
   end
 end

spec/workers/migrate_application_choices_worker_spec.rb

@@ -2,7 +2,11 @@
 
 RSpec.describe MigrateApplicationChoicesWorker do
   describe '#perform' do
-    it 'dups the working experiences and histories from application_form to choice' do
+    before do
+      TestSuiteTimeMachine.unfreeze!
+    end
+
+    it 'dups the working experiences and histories from application_form to choice', :with_audited do
       application_form = create(
         :completed_application_form,
         volunteering_experiences_count: 1,
@@ -31,7 +35,6 @@
         breakable: choice_with_data_migrated,
       )
       choice_ids = [choice.id, choice_with_data_migrated.id]
-      allow(Rails.logger).to receive(:info)
 
       expect {
         described_class.new.perform(choice_ids)
@@ -41,27 +44,32 @@
         .and not_change(choice_with_data_migrated.work_experiences, :count)
         .and not_change(choice_with_data_migrated.volunteering_experiences, :count)
         .and not_change(choice_with_data_migrated.work_history_breaks, :count)
-      expect(Rails.logger).to have_received(:info).with('No errors')
+        .and not_change(choice.own_and_associated_audits, :count)
+        .and not_change(choice.reload, :updated_at)
+        .and not_change(application_form.reload, :updated_at)
+        .and not_change(application_form.candidate, :updated_at)
     end
 
-    context 'with errors' do
-      it 'rescues ActiveRecord::RecordInvalid exceptions and logs the errors' do
+    context 'when env is production' do
+      it 'does not create work histories' do
         application_form = create(
           :completed_application_form,
           volunteering_experiences_count: 1,
           full_work_history: true,
         )
         choice = create(:application_choice, application_form:)
-        choice_ids = [choice.id]
 
-        # rubocop:disable RSpec/AnyInstance
-        allow_any_instance_of(ApplicationChoice).to receive(:work_experiences=)
-          .and_raise(ActiveRecord::RecordInvalid)
-        # rubocop:enable RSpec/AnyInstance
-        allow(Rails.logger).to receive(:info)
+        allow(HostingEnvironment).to receive(:production?).and_return(true)
 
-        described_class.new.perform(choice_ids)
-        expect(Rails.logger).to have_received(:info).with("Error choice id #{choice.id}: Record invalid")
+        expect {
+          described_class.new.perform([choice.id])
+        }.to not_change(choice.work_experiences, :count)
+          .and not_change(choice.volunteering_experiences, :count)
+          .and not_change(choice.work_history_breaks, :count)
+          .and not_change(choice.own_and_associated_audits, :count)
+          .and not_change(choice.reload, :updated_at)
+          .and not_change(application_form.reload, :updated_at)
+          .and not_change(application_form.candidate, :updated_at)
       end
     end
   end