From bc4045abd99936d70bd115ea37744dd3521afce0 Mon Sep 17 00:00:00 2001
From: xync <mixartemev@gmail.com>
Date: Thu, 21 May 2026 01:02:31 +0300
Subject: [PATCH] Fix db_default on ForeignKey/OneToOne dropped during
 _init_relations

When db_default is set on a ForeignKeyField/OneToOneField, the value
never reaches the generated DDL: `_init_relations` builds the implicit
`<fk>_id` key field by copying the related model's PK and patching a
small set of attributes from the FK object, but `db_default` is not in
that list. The schema editor then iterates fields_db_projection (which
contains the key field) and finds has_db_default() == False, so the
CREATE TABLE for the owning model has no DEFAULT clause on the FK column.

Add `db_default` to the attribute-copy tuple so it propagates from the
FK to the underlying column, mirroring how PR #2129 fixed the same
omission for non-relation fields.

Fixes #2199
---
 CHANGELOG.rst                              |  1 +
 tests/migrations/test_schema_editor_sql.py | 33 ++++++++++++++++++++++
 tortoise/apps.py                           |  2 +-
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index b111c9525..a6fa2cfae 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -21,6 +21,7 @@ Added
 Fixed
 ^^^^^
 - ``MigrationRecorder`` now uses parameterized queries; fixes MariaDB/MySQL rejecting ISO-8601 ``applied_at`` values. (#2132)
+- ``db_default`` on ``ForeignKeyField``/``OneToOneField`` now propagates to the underlying ``<fk>_id`` column, so ``CREATE TABLE`` emits the ``DEFAULT`` clause for FK columns. (#2199)
 
 1.1.7
 -----
diff --git a/tests/migrations/test_schema_editor_sql.py b/tests/migrations/test_schema_editor_sql.py
index ee9ca8860..30578f5f8 100644
--- a/tests/migrations/test_schema_editor_sql.py
+++ b/tests/migrations/test_schema_editor_sql.py
@@ -249,3 +249,36 @@ class Meta:
     sql = client.executed[0]
     assert 'CREATE TABLE "widget"' in sql
     assert "DEFAULT 'active'" in sql
+
+
+@pytest.mark.asyncio
+async def test_create_model_includes_db_default_on_fk() -> None:
+    """CreateModel should include DEFAULT clause for FK columns with db_default."""
+
+    class Dc(Model):
+        id = fields.IntField(pk=True)
+
+        class Meta:
+            table = "dc"
+            app = "models"
+
+    class App(Model):
+        id = fields.IntField(pk=True)
+        dc = fields.ForeignKeyField("models.Dc", db_default=2)
+
+        class Meta:
+            table = "app"
+            app = "models"
+
+    init_apps(Dc, App)
+
+    client = FakeClient("sql")
+    editor = TestSchemaEditor(client)
+
+    await editor.create_model(App)
+
+    assert len(client.executed) == 1
+    sql = client.executed[0]
+    assert 'CREATE TABLE "app"' in sql
+    assert '"dc_id"' in sql
+    assert "DEFAULT 2" in sql
diff --git a/tortoise/apps.py b/tortoise/apps.py
index f2be4800f..637ba142b 100644
--- a/tortoise/apps.py
+++ b/tortoise/apps.py
@@ -192,7 +192,7 @@ def init_fk_o2o_field(model: type[Model], field: str, is_o2o: bool = False) -> N
             key_field = f"{field}_id"
             key_fk_object.reference = fk_object
             key_fk_object.source_field = fk_object.source_field or key_field
-            for attr in ("index", "default", "null", "generated", "description"):
+            for attr in ("index", "default", "null", "generated", "description", "db_default"):
                 setattr(key_fk_object, attr, getattr(fk_object, attr))
             if is_o2o:
                 key_fk_object.pk = fk_object.pk