refactor write_export_archive to only hold MAX_XML_RECORDS in memory at a time

app/services/exports/lettings_log_export_service.rb

@@ -63,53 +63,58 @@ module Exports
       @storage_service.write_file(file_path, string_io)
     end
 
-    def get_archive_name(lettings_log, base_number, increment)
+    def get_archive_name(collection, base_number, increment)
-      return unless lettings_log.startdate
+      return unless collection
 
-      collection_start = lettings_log.collection_start_year
-      start_month = collection_start_date(lettings_log.startdate).strftime("%b")
-      end_month = collection_end_date(lettings_log.startdate).strftime("%b")
       base_number_str = "f#{base_number.to_s.rjust(4, '0')}"
       increment_str = "inc#{increment.to_s.rjust(4, '0')}"
-      "core_#{collection_start}_#{collection_start + 1}_#{start_month}_#{end_month}_#{base_number_str}_#{increment_str}".downcase
+      "core_#{collection}_#{collection + 1}_apr_mar_#{base_number_str}_#{increment_str}".downcase
     end
 
     def write_export_archive(export, collection, start_time, full_update)
       @logger.info("Writing export archives")
-      # Order lettings logs per archive
+      archive = get_archive_name(collection, export.base_number, export.increment_number) # archive name would be the same for all logs because they're already filtered by year (?)
-      lettings_logs = retrieve_lettings_logs(start_time, full_update).filter_by_year(collection)
+
-      return {} unless lettings_logs.exists?
+      # Write archive
-      
+      logs_count = retrieve_lettings_logs(start_time, full_update).filter_by_year(collection).count
-      archive_name = get_archive_name(lettings_logs.first, export.base_number, export.increment_number) #archive name would be the same for all logs because they're already filtered by year (?)
+      @logger.info("Writing #{archive} - #{logs_count} logs")
-      lettings_logs_per_archive = { archive_name => lettings_logs }
+      manifest_xml = build_manifest_xml(logs_count)
-
+      return {} if logs_count.zero?
-      # Write all archives
+
-      archive_datetimes = {}
+      zip_file = Zip::File.open_buffer(StringIO.new)
-      lettings_logs_per_archive.each do |archive, lettings_logs_to_export|
+      zip_file.add("manifest.xml", manifest_xml)
-        @logger.info("Writing #{archive} - #{lettings_logs_to_export.count} logs")
+
-        manifest_xml = build_manifest_xml(lettings_logs_to_export.count)
+      part_number = 1
-        zip_file = Zip::File.open_buffer(StringIO.new)
+      last_processed_marker = nil
-        zip_file.add("manifest.xml", manifest_xml)
+
-
+      loop do
-        part_number = 1
+        lettings_logs_slice = if last_processed_marker.present?
-        lettings_logs_to_export.each_slice(MAX_XML_RECORDS) do |lettings_logs_slice|
+                                retrieve_lettings_logs(start_time, full_update).filter_by_year(collection)
-          data_xml = build_export_xml(lettings_logs_slice)
+                                      .where("created_at > ?", last_processed_marker)
-          part_number_str = "pt#{part_number.to_s.rjust(3, '0')}"
+                                      .order(:created_at)
-          @logger.info("Adding #{archive}_#{part_number_str}.xml")
+                                      .limit(MAX_XML_RECORDS)
-          zip_file.add("#{archive}_#{part_number_str}.xml", data_xml)
+                              else
-          part_number += 1
+                                retrieve_lettings_logs(start_time, full_update).filter_by_year(collection)
-        end
+                                .order(:created_at)
-
+                                .limit(MAX_XML_RECORDS)
-        # Required by S3 to avoid Aws::S3::Errors::BadDigest
+                              end
-        zip_io = zip_file.write_buffer
+
-        zip_io.rewind
+        break if lettings_logs_slice.empty?
-        @logger.info("Writting #{archive}.zip")
+
-        @storage_service.write_file("#{archive}.zip", zip_io)
+        data_xml = build_export_xml(lettings_logs_slice)
-        archive_datetimes[archive] = Time.zone.now
+        part_number_str = "pt#{part_number.to_s.rjust(3, '0')}"
+        @logger.info("Adding #{archive}_#{part_number_str}.xml")
+        zip_file.add("#{archive}_#{part_number_str}.xml", data_xml)
+        part_number += 1
+        last_processed_marker = lettings_logs_slice.last.created_at
       end
-      # rubocop:enable Style/CombinableLoops
 
-      archive_datetimes
+      # Required by S3 to avoid Aws::S3::Errors::BadDigest
+      zip_io = zip_file.write_buffer
+      zip_io.rewind
+      @logger.info("Writting #{archive}.zip")
+      @storage_service.write_file("#{archive}.zip", zip_io)
+      { archive => Time.zone.now }
     end
 
     def retrieve_lettings_logs(start_time, full_update)