add migration to fix incorrect file counts on directories

src/metax_api/migrations/0033_auto_20210201_1551.py

@@ -0,0 +1,30 @@
+# Generated by Django 3.1.2 on 2021-02-01 13:51
+import logging
+
+from django.db import migrations
+
+logger = logging.getLogger(__name__)
+
+def recount_directory_files(apps, schema_editor):
+    Directory = apps.get_model('metax_api', 'Directory')
+    dirs_with_no_files = Directory.objects.filter(file_count=0, parent_directory_id=None)
+    logger.info(f"found {dirs_with_no_files.count()} directories without files")
+    aff_rows = 0
+    for dir in dirs_with_no_files:
+        dir.calculate_byte_size_and_file_count()
+        aff_rows += 1
+    logger.info(f"migration 0033 complete with {aff_rows} affected rows")
+
+
+def revert(apps, schema_editor):
+    pass
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('metax_api', '0032_auto_20201222_1321'),
+    ]
+
+    operations = [
+        migrations.RunPython(recount_directory_files, revert),
+    ]