core: improve performances on notification reads and display

core/migrations/0032_auto_20190909_0043.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.24 on 2019-09-08 22:43
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [("core", "0031_auto_20190906_1615")]
+
+    operations = [
+        migrations.AlterField(
+            model_name="notification",
+            name="viewed",
+            field=models.BooleanField(
+                db_index=True, default=False, verbose_name="viewed"
+            ),
+        )
+    ]