From 42a9e342ef57a9ffa5016f4f57da633a811d2c0f Mon Sep 17 00:00:00 2001
From: stvn <stvn@mit.edu>
Date: Wed, 24 Feb 2021 12:00:34 -0800
Subject: [PATCH] fix: Manually backfill config_id UUIDs again
The previous backfills handled NULL entries;
this handles empty strings.
The difficulty here was that since the empty string in an invalid UUID
(as opposed to None/NULL which is just "blank"), attempts to instantiate
models would fail, given the invalid data. This meant we couldn't use
the Django ORM to handle the migration entirely; we need to craft some
raw SQL to work-around these checks and limitations.
---
.../0009_backfill-empty-string-config-id.py | 72 +++++++++++++++++++
1 file changed, 72 insertions(+)
create mode 100644 lti_consumer/migrations/0009_backfill-empty-string-config-id.py
diff --git a/lti_consumer/migrations/0009_backfill-empty-string-config-id.py b/lti_consumer/migrations/0009_backfill-empty-string-config-id.py
new file mode 100644
index 0000000..30f6a9e
--- /dev/null
+++ b/lti_consumer/migrations/0009_backfill-empty-string-config-id.py
@@ -0,0 +1,72 @@
+"""
+Backfill empty config_id records
+
+We need to do this with raw SQL,
+otherwise the model fails upon instantiation,
+as the empty string is an invalid UUID.
+"""
+import uuid
+
+from django.db import connection
+from django.db import migrations
+
+
+sql_forward = """\
+UPDATE
+ lti_consumer_lticonfiguration
+SET
+ config_id = %s
+WHERE
+ id = %s
+;\
+"""
+
+sql_select_empty = """\
+SELECT
+ id
+FROM
+ lti_consumer_lticonfiguration
+WHERE
+ config_id = ""
+;\
+"""
+
+
+def _get_ids_with_empty_uuid():
+ """
+ Retrieve the list of primary keys for each entry with a blank config_id
+ """
+ with connection.cursor() as cursor:
+ cursor.execute(sql_select_empty)
+ for row in cursor.fetchall():
+ yield row[0]
+
+
+def _create_config_ids(apps, schema_editor):
+ """
+ Generate a UUID for rows missing one
+
+ Note: The model stores these without hyphens.
+ """
+ for _id in _get_ids_with_empty_uuid():
+ config_id = uuid.uuid4()
+ config_id = str(config_id)
+ config_id = config_id.replace('-', '')
+ schema_editor.execute(sql_forward, [
+ config_id,
+ _id,
+ ])
+
+
+class Migration(migrations.Migration):
+ """
+ Backfill empty config_id records
+ """
+
+ dependencies = [
+ ('lti_consumer', '0008_fix_uuid_backfill'),
+ ]
+
+ operations = [
+ migrations.RunPython(_create_config_ids, atomic=False),
+ ]
--
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