Added missing index on date field.

fix #2403

modoboa/maillog/migrations/0003_auto_20211108_1652.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.2.24 on 2021-11-08 15:52
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('maillog', '0002_auto_20200916_1346'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='maillog',
+            name='date',
+            field=models.DateTimeField(db_index=True),
+        ),
+    ]

modoboa/maillog/models.py

@@ -7,7 +7,7 @@ class Maillog(models.Model):
     """A model to store message logs."""
 
     queue_id = models.CharField(max_length=50)
-    date = models.DateTimeField()
+    date = models.DateTimeField(db_index=True)
     sender = models.EmailField()
     rcpt = models.EmailField()
     original_rcpt = models.EmailField(null=True)