Use raw SQL migration to improve performance

isic/ingest/migrations/0038_migrate_copyright_license.py

@@ -1,18 +1,13 @@
 # Generated by Django 4.1.10 on 2023-07-31 22:25
 
-from django.db import migrations
+from django.db import connection, migrations
 
 
 def migrate_default_copyright_license(apps, schema_editor):
-    Accession = apps.get_model("ingest", "Accession")
-
-    objs = []
-    for accession in (
-        Accession.objects.select_related("cohort").filter(copyright_license=None).iterator()
-    ):
-        accession.copyright_license = accession.cohort.default_copyright_license
-        objs.append(accession)
-    Accession.objects.bulk_update(objs, ["copyright_license"], batch_size=1_000)
+    with connection.cursor() as cursor:
+        cursor.execute(
+            "update ingest_accession set copyright_license = ingest_cohort.default_copyright_license from ingest_cohort where ingest_accession.cohort_id = ingest_cohort.id"  # noqa: E501
+        )
 
 
 class Migration(migrations.Migration):