Analytics: create DB index on PageView.date (#10426)

We use this field to run cleaup
tasks (`readthedocs.analytics.tasks.delete_old_page_counts`). Having an index on
this field will help a lot to improve these queries.

Related readthedocs/readthedocs-ops#1291

Author: humitos

readthedocs/analytics/migrations/0007_index_on_pageview_date.py

@@ -0,0 +1,19 @@
+# Generated by Django 3.2.19 on 2023-06-13 11:12
+
+import datetime
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("analytics", "0006_alter_pageview_id"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="pageview",
+            name="date",
+            field=models.DateField(db_index=True, default=datetime.date.today),
+        ),
+    ]

readthedocs/analytics/models.py

@@ -82,7 +82,7 @@ class PageView(models.Model):
         blank=True,
     )
     view_count = models.PositiveIntegerField(default=0)
-    date = models.DateField(default=datetime.date.today)
+    date = models.DateField(default=datetime.date.today, db_index=True)
     status = models.PositiveIntegerField(
         default=200,
         help_text=_("HTTP status code"),