Optimise DocumentLink creation in fixception migration

src/documents/migrations/0014_auto_20180502_0852.py

@@ -10,6 +10,7 @@ def transcription_to_document(apps, schema_editor):
     DocumentLink = apps.get_model('documents', 'DocumentLink')
     nb = Transcription.objects.count()
     last = 0
+    links = []
     for i, ts in enumerate(Transcription.objects.all()):
         percent = int(100.0 * (i + 1) / nb)
         if percent % 5 == 0 and last != percent:
@@ -21,7 +22,9 @@ def transcription_to_document(apps, schema_editor):
         ts.save()
         max_order_dl = DocumentLink.objects.filter(parent_id=ts.zone.document.id).order_by('-order').first()
         order = 0 if max_order_dl is None else max_order_dl.order + 1
-        DocumentLink.objects.create(parent_id=ts.zone.document.id, child_id=doc.id, order=order)
+        links.append(DocumentLink(parent_id=ts.zone.document.id, child_id=doc.id, order=order))
+    print('Saving document links...')
+    DocumentLink.objects.bulk_create(links)
 
 
 class Migration(migrations.Migration):