Query directly for services with high failure rate

app/dao/services_dao.py

@@ -4,6 +4,7 @@ from datetime import date, datetime, timedelta
 from notifications_utils.statsd_decorators import statsd
 from sqlalchemy.sql.expression import asc, case, and_, func
 from sqlalchemy.orm import joinedload
+from sqlalchemy import cast, Float
 from flask import current_app
 
 from app import db
@@ -44,6 +45,7 @@ from app.models import (
     KEY_TYPE_TEST,
     NHS_ORGANISATION_TYPES,
     NON_CROWN_ORGANISATION_TYPES,
+    NOTIFICATION_PERMANENT_FAILURE,
     SMS_TYPE,
     LETTER_TYPE,
 )
@@ -544,12 +546,10 @@ def dao_find_services_sending_to_tv_numbers(start_date, end_date, threshold=100)
     ).all()
 
 
-def dao_find_real_sms_notification_count_by_status_for_live_services(start_date, end_date):
-    #  only works within services' retention period
-    return db.session.query(
-        Notification.service_id.label('service_id'),
-        Notification.status.label('status'),
-        func.count(Notification.id).label('count')
+def dao_find_services_with_high_failure_rates(start_date, end_date, threshold=100):
+    subquery = db.session.query(
+        func.count(Notification.id).label('total_count'),
+        Notification.service_id.label('service_id')
     ).filter(
         Notification.service_id == Service.id,
         Notification.created_at >= start_date,
@@ -561,5 +561,35 @@ def dao_find_real_sms_notification_count_by_status_for_live_services(start_date,
         Service.active == True,
     ).group_by(
         Notification.service_id,
-        Notification.status
-    ).all()
+    ).having(
+        func.count(Notification.id) >= threshold
+    )
+
+    subquery = subquery.subquery()
+
+    query = db.session.query(
+        Notification.service_id.label('service_id'),
+        func.count(Notification.id).label('permanent_failure_count'),
+        subquery.c.total_count.label('total_count'),
+        (cast(func.count(Notification.id), Float) / cast(subquery.c.total_count, Float)).label('permanent_failure_rate')
+    ).join(
+        subquery,
+        subquery.c.service_id == Notification.service_id
+    ).filter(
+        Notification.service_id == Service.id,
+        Notification.created_at >= start_date,
+        Notification.created_at <= end_date,
+        Notification.key_type != KEY_TYPE_TEST,
+        Notification.notification_type == SMS_TYPE,
+        Notification.status == NOTIFICATION_PERMANENT_FAILURE,
+        Service.restricted == False,  # noqa
+        Service.research_mode == False,
+        Service.active == True,
+    ).group_by(
+        Notification.service_id,
+        subquery.c.total_count
+    ).having(
+        cast(func.count(Notification.id), Float) / cast(subquery.c.total_count, Float) >= 0.25
+    )
+
+    return query.all()