Add db index. Advances BiscuIT-ng#55.

biscuit/apps/exlibris/migrations/0002_db_indexes.py

+# Generated by Django 2.2.4 on 2019-09-04 13:22
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('core', '0001_initial'),
+        ('exlibris', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AddIndex(
+            model_name='bookcopy',
+            index=models.Index(fields=['barcode'], name='exlibris_bo_co_barc_55ac33_idx'),
+        ),
+    ]

biscuit/apps/exlibris/models.py

@@ -88,3 +88,4 @@ class BookCopy(models.Model):
 
     class Meta:
         ordering = ['book__title', 'book__year', 'book__edition', 'copy_num']
+        indexes = [models.Index(fields=['barcode'])]