user: migrating to serial user ID #19

osmcal/migrations/0023_user_primary_key.py

@@ -0,0 +1,61 @@
+from django.db import migrations, models
+
+"""
+Hi! I made this because I can't stop making the same mistake: Never use a third-party ID as foreign
+key, because every change will be painful. I am fixing this mistake here: We're going to walk over
+all tables that reference osmcal_user.osm_id and replace this with a serial id.
+This involves a little bit of fiddling, as you might see.
+"""
+
+user_id_dependent_tables = [
+    ("osmcal_eventlog", "created_by_id", "osmcal_eventlog_created_by_id_89c62fed_fk_osmcal_user_osm_id"),
+    ("osmcal_eventparticipation", "user_id", "osmcal_eventparticip_user_id_8a2dfe0f_fk_osmcal_us"),
+    ("osmcal_participationanswer", "user_id", "osmcal_participation_user_id_93228060_fk_osmcal_us"),
+    ("osmcal_user_groups", "user_id", "osmcal_user_groups_user_id_c9d0a3d1_fk_osmcal_user_osm_id"),
+    ("osmcal_user_user_permissions", "user_id", "osmcal_user_user_per_user_id_1ecd1641_fk_osmcal_us"),
+    ("django_admin_log", "user_id", "django_admin_log_user_id_c564eba6_fk_osmcal_user_osm_id"),
+]
+
+
+def conversion_sql():
+    sql = ""
+    for t in user_id_dependent_tables:
+        sql += """
+        ALTER TABLE {0} DROP CONSTRAINT {2};
+        UPDATE {0} SET {1} = (SELECT id FROM osmcal_user WHERE osm_id = {0}.{1});
+        ALTER TABLE {0} ADD CONSTRAINT {2} FOREIGN KEY ({1}) REFERENCES osmcal_user (id);
+        """.format(*t)
+    return sql
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('osmcal', '0022_event_cancelled'),
+    ]
+
+    operations = [
+        migrations.SeparateDatabaseAndState(
+            database_operations=[
+                migrations.RunSQL([
+                    'ALTER TABLE osmcal_user ADD column id serial UNIQUE;',
+                    conversion_sql(),
+                    'ALTER TABLE osmcal_user DROP CONSTRAINT osmcal_user_pkey;',
+                    'ALTER TABLE osmcal_user ADD PRIMARY KEY (id);',
+                ])
+            ],
+            state_operations=[
+                migrations.AddField(
+                    model_name='user',
+                    name='id',
+                    field=models.AutoField(primary_key=True, serialize=False),
+                    preserve_default=False,
+                ),
+                migrations.AlterField(
+                    model_name='user',
+                    name='osm_id',
+                    field=models.IntegerField(),
+                ),
+            ]
+        )
+    ]

osmcal/models.py

@@ -114,7 +114,8 @@ class EventLog(models.Model):
 
 
 class User(AbstractUser):
-    osm_id = models.IntegerField(primary_key=True)
+    id = models.AutoField(primary_key=True)
+    osm_id = models.IntegerField()
     name = models.CharField(max_length=255)
 
     def save(self, *args, **kwargs):