Clarify SQLite can't drop foreign key constraints (#123898)

homeassistant/components/recorder/migration.py

@@ -585,7 +585,18 @@ def _modify_columns(
 def _update_states_table_with_foreign_key_options(
     session_maker: Callable[[], Session], engine: Engine
 ) -> None:
-    """Add the options to foreign key constraints."""
+    """Add the options to foreign key constraints.
+
+    This is not supported for SQLite because it does not support
+    dropping constraints.
+    """
+
+    if engine.dialect.name not in (SupportedDialect.MYSQL, SupportedDialect.POSTGRESQL):
+        raise RuntimeError(
+            "_update_states_table_with_foreign_key_options not supported for "
+            f"{engine.dialect.name}"
+        )
+
     inspector = sqlalchemy.inspect(engine)
     tmp_states_table = Table(TABLE_STATES, MetaData())
     alters = [
@@ -633,7 +644,17 @@ def _update_states_table_with_foreign_key_options(
 def _drop_foreign_key_constraints(
     session_maker: Callable[[], Session], engine: Engine, table: str, column: str
 ) -> tuple[bool, list[tuple[str, str, ReflectedForeignKeyConstraint]]]:
-    """Drop foreign key constraints for a table on specific columns."""
+    """Drop foreign key constraints for a table on specific columns.
+
+    This is not supported for SQLite because it does not support
+    dropping constraints.
+    """
+
+    if engine.dialect.name not in (SupportedDialect.MYSQL, SupportedDialect.POSTGRESQL):
+        raise RuntimeError(
+            f"_drop_foreign_key_constraints not supported for {engine.dialect.name}"
+        )
+
     inspector = sqlalchemy.inspect(engine)
     dropped_constraints = [
         (table, column, foreign_key)
@@ -1026,7 +1047,17 @@ class _SchemaVersion11Migrator(_SchemaVersionMigrator, target_version=11):
     def _apply_update(self) -> None:
         """Version specific update method."""
         _create_index(self.session_maker, "states", "ix_states_old_state_id")
-        _update_states_table_with_foreign_key_options(self.session_maker, self.engine)
+
+        # _update_states_table_with_foreign_key_options first drops foreign
+        # key constraints, and then re-adds them with the correct settings.
+        # This is not supported by SQLite
+        if self.engine.dialect.name in (
+            SupportedDialect.MYSQL,
+            SupportedDialect.POSTGRESQL,
+        ):
+            _update_states_table_with_foreign_key_options(
+                self.session_maker, self.engine
+            )
 
 
 class _SchemaVersion12Migrator(_SchemaVersionMigrator, target_version=12):
@@ -1080,9 +1111,14 @@ class _SchemaVersion15Migrator(_SchemaVersionMigrator, target_version=15):
 class _SchemaVersion16Migrator(_SchemaVersionMigrator, target_version=16):
     def _apply_update(self) -> None:
         """Version specific update method."""
-        _drop_foreign_key_constraints(
-            self.session_maker, self.engine, TABLE_STATES, "old_state_id"
-        )
+        # Dropping foreign key constraints is not supported by SQLite
+        if self.engine.dialect.name in (
+            SupportedDialect.MYSQL,
+            SupportedDialect.POSTGRESQL,
+        ):
+            _drop_foreign_key_constraints(
+                self.session_maker, self.engine, TABLE_STATES, "old_state_id"
+            )
 
 
 class _SchemaVersion17Migrator(_SchemaVersionMigrator, target_version=17):

tests/components/recorder/test_migrate.py

@@ -1053,3 +1053,51 @@ def test_delete_foreign_key_violations_unsupported_engine(
         RuntimeError, match="_delete_foreign_key_violations not supported for sqlite"
     ):
         migration._delete_foreign_key_violations(session_maker, engine, "", "", "", "")
+
+
+def test_drop_foreign_key_constraints_unsupported_engine(
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    """Test calling _drop_foreign_key_constraints with an unsupported engine."""
+
+    connection = Mock()
+    connection.execute = Mock(side_effect=InternalError(None, None, None))
+    session = Mock()
+    session.connection = Mock(return_value=connection)
+    instance = Mock()
+    instance.get_session = Mock(return_value=session)
+    engine = Mock()
+    engine.dialect = Mock()
+    engine.dialect.name = "sqlite"
+
+    session_maker = Mock(return_value=session)
+    with pytest.raises(
+        RuntimeError, match="_drop_foreign_key_constraints not supported for sqlite"
+    ):
+        migration._drop_foreign_key_constraints(session_maker, engine, "", "")
+
+
+def test_update_states_table_with_foreign_key_options_unsupported_engine(
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    """Test calling function with an unsupported engine.
+
+    This tests _update_states_table_with_foreign_key_options.
+    """
+
+    connection = Mock()
+    connection.execute = Mock(side_effect=InternalError(None, None, None))
+    session = Mock()
+    session.connection = Mock(return_value=connection)
+    instance = Mock()
+    instance.get_session = Mock(return_value=session)
+    engine = Mock()
+    engine.dialect = Mock()
+    engine.dialect.name = "sqlite"
+
+    session_maker = Mock(return_value=session)
+    with pytest.raises(
+        RuntimeError,
+        match="_update_states_table_with_foreign_key_options not supported for sqlite",
+    ):
+        migration._update_states_table_with_foreign_key_options(session_maker, engine)