add db_index on url field

archivebox/core/migrations/0019_auto_20210401_0654.py

@@ -0,0 +1,18 @@
+# Generated by Django 3.1.3 on 2021-04-01 06:54
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('core', '0018_auto_20210327_0952'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='snapshot',
+            name='url',
+            field=models.URLField(db_index=True, unique=True),
+        ),
+    ]