From a637c8eb92007c33704f90bcf61c60c6125556d3 Mon Sep 17 00:00:00 2001
From: Rebecca Law <rebecca.law@digital.cabinet-office.gov.uk>
Date: Tue, 20 Apr 2021 13:42:20 +0100
Subject: [PATCH] Add unique key on annual_billing for service_id +
 financial_year_start.

This is an extra precaution for the table to ensure data integrity. Since we only update/insert the data using the annual_billing_dao methods the integrity is in tact. I've check the data on preview, staging and prod there are no violations of this unique key.
---
 app/dao/annual_billing_dao.py                 |  2 +-
 app/models.py                                 |  3 +++
 .../0351_unique_key_annual_billing.py         | 22 +++++++++++++++++++
 3 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 migrations/versions/0351_unique_key_annual_billing.py

diff --git a/app/dao/annual_billing_dao.py b/app/dao/annual_billing_dao.py
index 9497b0d75..ffad11ade 100644
--- a/app/dao/annual_billing_dao.py
+++ b/app/dao/annual_billing_dao.py
@@ -102,7 +102,7 @@ def set_default_free_allowance_for_service(service, year_start=None):
                                 f"{default_free_sms_fragment_limits['other'][year_start]}")
         free_allowance = default_free_sms_fragment_limits['other'][year_start]
 
-    dao_create_or_update_annual_billing_for_year(
+    return dao_create_or_update_annual_billing_for_year(
         service.id,
         free_allowance,
         year_start
diff --git a/app/models.py b/app/models.py
index 9d0db0563..2b91d9395 100644
--- a/app/models.py
+++ b/app/models.py
@@ -579,6 +579,9 @@ class AnnualBilling(db.Model):
     UniqueConstraint('financial_year_start', 'service_id', name='ix_annual_billing_service_id')
     service = db.relationship(Service, backref=db.backref("annual_billing", uselist=True))
 
+    __table_args__ = (UniqueConstraint(
+        'service_id', 'financial_year_start', name='uix_service_id_financial_year_start'),)
+
     def serialize_free_sms_items(self):
         return {
             'free_sms_fragment_limit': self.free_sms_fragment_limit,
diff --git a/migrations/versions/0351_unique_key_annual_billing.py b/migrations/versions/0351_unique_key_annual_billing.py
new file mode 100644
index 000000000..2f814b815
--- /dev/null
+++ b/migrations/versions/0351_unique_key_annual_billing.py
@@ -0,0 +1,22 @@
+"""
+
+Revision ID: 0351_unique_key_annual_billing
+Revises: 0350_update_rates
+Create Date: 2021-04-12 09:02:45.098875
+
+"""
+from alembic import op
+
+revision = '0351_unique_key_annual_billing'
+down_revision = '0350_update_rates'
+
+
+def upgrade():
+    op.create_unique_constraint(
+        'uix_service_id_financial_year_start', 'annual_billing', ['service_id', 'financial_year_start']
+    )
+
+
+def downgrade():
+    op.drop_constraint('uix_service_id_financial_year_start', 'annual_billing', type_='unique')
+