Merge pull request #9477 from DFE-Digital/dd/move-migrations-to-worke…

…r-jobs-to-tackle-each-data-export-in-isolation

Only select the Data Export ID to enqueue the migration jobs

app/services/data_migrations/migrate_data_export_data_to_file.rb

@@ -4,7 +4,7 @@ class MigrateDataExportDataToFile
     MANUAL_RUN = true
 
     def change
-      BatchDelivery.new(relation: DataExport.all, stagger_over: 4.hours, batch_size: 10).each do |next_batch_time, data_exports|
+      BatchDelivery.new(relation: DataExport.select(:id), stagger_over: 4.hours, batch_size: 10).each do |next_batch_time, data_exports|
         data_exports.each do |data_export|
           DataExportFileMigrationWorker.perform_at(next_batch_time, data_export.id)
         end