Backend specific migration fixes

CHANGELOG.rst

@@ -8,6 +8,22 @@ Changelog
 1.1
 ===
 
+1.1.3
+-----
+
+Added
+^^^^^
+- ``RandomHex`` dialect-aware ``SqlDefault`` subclass for generating random hex strings across all backends. (#2108)
+- ``Meta.constraints`` support on models — named ``UniqueConstraint`` objects are now captured by the migration autodetector, enabling ``AddConstraint``/``RemoveConstraint`` generation via ``makemigrations``. (#2108)
+- MySQL schema editor: ``_alter_field`` override using ``MODIFY COLUMN`` for NULL/NOT NULL changes; backtick-quoted ``ALTER_FIELD_*`` templates. (#2108)
+- MSSQL schema editor: ``_alter_field`` override with ``ALTER COLUMN`` for nullability, named default constraint management via ``sys.default_constraints``, bracket-quoted templates, and self-referencing FK CASCADE → NO ACTION downgrade. (#2108)
+
+Fixed
+^^^^^
+- MySQL migrations: ``ALTER COLUMN ... SET NOT NULL`` / ``DROP NOT NULL`` now correctly emits ``MODIFY COLUMN col type NOT NULL/NULL``. (#2108)
+- MSSQL migrations: ``DELETE_CONSTRAINT_TEMPLATE`` and ``UNIQUE_CONSTRAINT_CREATE_TEMPLATE`` now use bracket quoting ``[name]`` instead of double quotes. (#2108)
+- MSSQL migrations: self-referencing foreign keys with ``CASCADE`` no longer fail with error 1785; automatically downgraded to ``NO ACTION``. (#2108)
+
 1.1.2
 -----
 

examples/comprehensive_migrations_project/migrations/0011_populate_computed_fields.py

@@ -5,6 +5,13 @@
 from tortoise import migrations
 from tortoise.migrations import operations as ops
 
+_CONCAT_SQL = {
+    "postgres": "UPDATE employee SET full_name = first_name || ' ' || last_name WHERE full_name IS NULL",
+    "sqlite": "UPDATE employee SET full_name = first_name || ' ' || last_name WHERE full_name IS NULL",
+    "mysql": "UPDATE employee SET full_name = CONCAT(first_name, ' ', last_name) WHERE full_name IS NULL",
+    "mssql": "UPDATE employee SET full_name = first_name + ' ' + last_name WHERE full_name IS NULL",
+}
+
 
 def populate_total_amount(apps, schema_editor):
     """Convert total_cents to total_amount (cents to dollars)."""
@@ -30,6 +37,25 @@ async def do_clear():
     return do_clear()
 
 
+def populate_full_name(apps, schema_editor):
+    """Populate full_name from first_name + last_name using dialect-specific SQL."""
+    sql = _CONCAT_SQL[schema_editor.DIALECT]
+
+    async def do_populate():
+        await schema_editor.client.execute_query(sql)
+
+    return do_populate()
+
+
+def clear_full_name(apps, schema_editor):
+    """Reverse: Clear full_name field."""
+
+    async def do_clear():
+        await schema_editor.client.execute_query("UPDATE employee SET full_name = NULL")
+
+    return do_clear()
+
+
 class Migration(migrations.Migration):
     dependencies = [("erp", "0010_add_computed_fields")]
 
@@ -40,8 +66,8 @@ class Migration(migrations.Migration):
             code=populate_total_amount,
             reverse_code=clear_total_amount,
         ),
-        ops.RunSQL(
-            sql="UPDATE employee SET full_name = first_name || ' ' || last_name WHERE full_name IS NULL",
-            reverse_sql="UPDATE employee SET full_name = NULL",
+        ops.RunPython(
+            code=populate_full_name,
+            reverse_code=clear_full_name,
         ),
     ]

examples/comprehensive_migrations_project/migrations/0017_create_bad_sorted_fk.py

@@ -9,6 +9,28 @@ class Migration(migrations.Migration):
     initial = False
 
     operations = [
+        ops.CreateModel(
+            name="Warehouse",
+            fields=[
+                (
+                    "id",
+                    fields.IntField(generated=True, primary_key=True, unique=True, db_index=True),
+                ),
+                ("name", fields.CharField(max_length=200)),
+                ("location", fields.CharField(max_length=300)),
+                (
+                    "is_active",
+                    fields.BooleanField(default=True, generated=False, null=False, unique=False),
+                ),
+            ],
+            options={
+                "table": "warehouse",
+                "app": "erp",
+                "pk_attr": "id",
+                "table_description": "Warehouse entity - storage location for inventory.",
+            },
+            bases=["Model"],
+        ),
         ops.CreateModel(
             name="Alert",
             fields=[
@@ -42,26 +64,4 @@ class Migration(migrations.Migration):
             },
             bases=["Model"],
         ),
-        ops.CreateModel(
-            name="Warehouse",
-            fields=[
-                (
-                    "id",
-                    fields.IntField(generated=True, primary_key=True, unique=True, db_index=True),
-                ),
-                ("name", fields.CharField(max_length=200)),
-                ("location", fields.CharField(max_length=300)),
-                (
-                    "is_active",
-                    fields.BooleanField(default=True, generated=False, null=False, unique=False),
-                ),
-            ],
-            options={
-                "table": "warehouse",
-                "app": "erp",
-                "pk_attr": "id",
-                "table_description": "Warehouse entity - storage location for inventory.",
-            },
-            bases=["Model"],
-        ),
     ]

examples/comprehensive_migrations_project/migrations/0021_add_sql_default_expressions.py

@@ -1,5 +1,5 @@
 from tortoise import fields, migrations
-from tortoise.fields.db_defaults import Now, SqlDefault
+from tortoise.fields.db_defaults import Now, RandomHex
 from tortoise.migrations import operations as ops
 
 
@@ -17,8 +17,6 @@ class Migration(migrations.Migration):
         ops.AddField(
             model_name="Product",
             name="tracking_id",
-            field=fields.CharField(
-                null=True, db_default=SqlDefault("(lower(hex(randomblob(16))))"), max_length=36
-            ),
+            field=fields.CharField(null=True, db_default=RandomHex(), max_length=36),
         ),
     ]

examples/comprehensive_migrations_project/migrations/0022_add_employee_constraints.py

@@ -0,0 +1,22 @@
+from tortoise import migrations
+from tortoise.migrations import operations as ops
+from tortoise.migrations.constraints import UniqueConstraint
+
+
+class Migration(migrations.Migration):
+    dependencies = [("erp", "0021_add_sql_default_expressions")]
+
+    initial = False
+
+    operations = [
+        ops.AddConstraint(
+            model_name="Employee",
+            constraint=UniqueConstraint(fields=("first_name", "last_name"), name=None),
+        ),
+        ops.AddConstraint(
+            model_name="Employee",
+            constraint=UniqueConstraint(
+                fields=("email", "department_id"), name="uq_employee_email_dept"
+            ),
+        ),
+    ]

examples/comprehensive_migrations_project/migrations/0023_drop_employee_constraints.py

@@ -0,0 +1,21 @@
+from tortoise import migrations
+from tortoise.migrations import operations as ops
+
+
+class Migration(migrations.Migration):
+    dependencies = [("erp", "0022_add_employee_constraints")]
+
+    initial = False
+
+    operations = [
+        ops.RemoveConstraint(
+            model_name="Employee",
+            name=None,
+            fields=["first_name", "last_name"],
+        ),
+        ops.RemoveConstraint(
+            model_name="Employee",
+            name="uq_employee_email_dept",
+            fields=None,
+        ),
+    ]

examples/comprehensive_migrations_project/models.py

@@ -11,7 +11,7 @@
 from enum import Enum, IntEnum
 
 from tortoise import fields, models
-from tortoise.fields import Now, SqlDefault
+from tortoise.fields import Now, RandomHex
 
 
 class OrderStatus(IntEnum):
@@ -121,7 +121,7 @@ class Product(models.Model):
     tracking_id = fields.CharField(
         max_length=36,
         null=True,
-        db_default=SqlDefault("(lower(hex(randomblob(16))))"),
+        db_default=RandomHex(),
     )
     created_at = fields.DatetimeField(db_default=Now())