Update migration command to enable/disable transactions

beanie/executors/migrate.py

@@ -53,6 +53,7 @@ def __init__(self, **kwargs):
             or self.get_from_toml("allow_index_dropping")
             or False
         )
+        self.use_transaction = bool(kwargs.get("use_transaction"))
 
     @staticmethod
     def get_env_value(field_name) -> Any:
@@ -111,7 +112,9 @@ async def run_migrate(settings: MigrationSettings):
         direction=settings.direction, distance=settings.distance
     )
     await root.run(
-        mode=mode, allow_index_dropping=settings.allow_index_dropping
+        mode=mode,
+        allow_index_dropping=settings.allow_index_dropping,
+        use_transaction=settings.use_transaction,
     )
 
 
@@ -160,13 +163,23 @@ async def run_migrate(settings: MigrationSettings):
     default=False,
     help="if allow-index-dropping is set, Beanie will drop indexes from your collection",
 )
+@click.option(
+    "--use-transaction/--no-use-transaction",
+    required=False,
+    default=True,
+    help="Enable or disable the use of transactions during migration. "
+    "When enabled (--use-transaction), Beanie uses transactions for migration, "
+    "which necessitates a replica set. When disabled (--no-use-transaction), "
+    "migrations occur without transactions.",
+)
 def migrate(
     direction,
     distance,
     connection_uri,
     database_name,
     path,
     allow_index_dropping,
+    use_transaction,
 ):
     settings_kwargs = {}
     if direction:
@@ -181,6 +194,7 @@ def migrate(
         settings_kwargs["path"] = path
     if allow_index_dropping:
         settings_kwargs["allow_index_dropping"] = allow_index_dropping
+    settings_kwargs["use_transaction"] = use_transaction
     settings = MigrationSettings(**settings_kwargs)
 
     asyncio.run(run_migrate(settings))

beanie/migrations/controllers/base.py

@@ -5,6 +5,9 @@
 
 
 class BaseMigrationController(ABC):
+    def __init__(self, function):
+        self.function = function
+
     @abstractmethod
     async def run(self, session):
         pass

beanie/migrations/runner.py

@@ -1,7 +1,9 @@
 import logging
 from importlib.machinery import SourceFileLoader
 from pathlib import Path
-from typing import Optional, Type
+from typing import List, Optional, Type
+
+from motor.motor_asyncio import AsyncIOMotorClientSession, AsyncIOMotorDatabase
 
 from beanie.migrations.controllers.iterative import BaseMigrationController
 from beanie.migrations.database import DBHandler
@@ -55,7 +57,12 @@ async def update_current_migration(self):
         await self.clean_current_migration()
         await MigrationLog(is_current=True, name=self.name).insert()
 
-    async def run(self, mode: RunningMode, allow_index_dropping: bool):
+    async def run(
+        self,
+        mode: RunningMode,
+        allow_index_dropping: bool,
+        use_transaction: bool,
+    ):
         """
         Migrate
 
@@ -71,7 +78,8 @@ async def run(self, mode: RunningMode, allow_index_dropping: bool):
                 logger.info("Running migrations forward without limit")
                 while True:
                     await migration_node.run_forward(
-                        allow_index_dropping=allow_index_dropping
+                        allow_index_dropping=allow_index_dropping,
+                        use_transaction=use_transaction,
                     )
                     migration_node = migration_node.next_migration
                     if migration_node is None:
@@ -80,7 +88,8 @@ async def run(self, mode: RunningMode, allow_index_dropping: bool):
                 logger.info(f"Running {mode.distance} migrations forward")
                 for i in range(mode.distance):
                     await migration_node.run_forward(
-                        allow_index_dropping=allow_index_dropping
+                        allow_index_dropping=allow_index_dropping,
+                        use_transaction=use_transaction,
                     )
                     migration_node = migration_node.next_migration
                     if migration_node is None:
@@ -91,7 +100,8 @@ async def run(self, mode: RunningMode, allow_index_dropping: bool):
                 logger.info("Running migrations backward without limit")
                 while True:
                     await migration_node.run_backward(
-                        allow_index_dropping=allow_index_dropping
+                        allow_index_dropping=allow_index_dropping,
+                        use_transaction=use_transaction,
                     )
                     migration_node = migration_node.prev_migration
                     if migration_node is None:
@@ -100,30 +110,41 @@ async def run(self, mode: RunningMode, allow_index_dropping: bool):
                 logger.info(f"Running {mode.distance} migrations backward")
                 for i in range(mode.distance):
                     await migration_node.run_backward(
-                        allow_index_dropping=allow_index_dropping
+                        allow_index_dropping=allow_index_dropping,
+                        use_transaction=use_transaction,
                     )
                     migration_node = migration_node.prev_migration
                     if migration_node is None:
                         break
 
-    async def run_forward(self, allow_index_dropping):
+    async def run_forward(
+        self, allow_index_dropping: bool, use_transaction: bool
+    ):
         if self.forward_class is not None:
             await self.run_migration_class(
-                self.forward_class, allow_index_dropping=allow_index_dropping
+                self.forward_class,
+                allow_index_dropping=allow_index_dropping,
+                use_transaction=use_transaction,
             )
         await self.update_current_migration()
 
-    async def run_backward(self, allow_index_dropping):
+    async def run_backward(
+        self, allow_index_dropping: bool, use_transaction: bool
+    ):
         if self.backward_class is not None:
             await self.run_migration_class(
-                self.backward_class, allow_index_dropping=allow_index_dropping
+                self.backward_class,
+                allow_index_dropping=allow_index_dropping,
+                use_transaction=use_transaction,
             )
         if self.prev_migration is not None:
             await self.prev_migration.update_current_migration()
         else:
             await self.clean_current_migration()
 
-    async def run_migration_class(self, cls: Type, allow_index_dropping: bool):
+    async def run_migration_class(
+        self, cls: Type, allow_index_dropping: bool, use_transaction: bool
+    ):
         """
         Run Backward or Forward migration class
 
@@ -142,19 +163,35 @@ async def run_migration_class(self, cls: Type, allow_index_dropping: bool):
         if client is None:
             raise RuntimeError("client must not be None")
         async with await client.start_session() as s:
-            async with s.start_transaction():
-                for migration in migrations:
-                    for model in migration.models:
-                        await init_beanie(
-                            database=db,
-                            document_models=[model],  # type: ignore
-                            allow_index_dropping=allow_index_dropping,
-                        )  # TODO this is slow
-                    logger.info(
-                        f"Running migration {migration.function.__name__} "
-                        f"from module {self.name}"
+            if use_transaction:
+                async with s.start_transaction():
+                    await self.run_migrations(
+                        migrations, db, allow_index_dropping, s
                     )
-                    await migration.run(session=s)
+            else:
+                await self.run_migrations(
+                    migrations, db, allow_index_dropping, s
+                )
+
+    async def run_migrations(
+        self,
+        migrations: List[BaseMigrationController],
+        db: AsyncIOMotorDatabase,
+        allow_index_dropping: bool,
+        session: AsyncIOMotorClientSession,
+    ) -> None:
+        for migration in migrations:
+            for model in migration.models:
+                await init_beanie(
+                    database=db,
+                    document_models=[model],  # type: ignore
+                    allow_index_dropping=allow_index_dropping,
+                )  # TODO this is slow
+            logger.info(
+                f"Running migration {migration.function.__name__} "
+                f"from module {self.name}"
+            )
+            await migration.run(session=session)
 
     @classmethod
     async def build(cls, path: Path):

docs/tutorial/migrations.md

@@ -1,6 +1,5 @@
 ## Attention!
 
-Migrations use transactions inside. They work only with **MongoDB replica sets**
 
 ## Create
 
@@ -17,6 +16,8 @@ Each one contains instructions to roll migration respectively forward and backwa
 
 ## Run
 
+**Attention**: By default, migrations use transactions. This approach only works with  **MongoDB replica sets**. If you prefer to run migrations without transactions, pass the `--no-use-transaction` flag to the `migrate` command. However, be aware that this approach is risky, as there is no way to roll back migrations without transactions.
+
 To roll one forward migration, run:
 
 ```shell
@@ -26,7 +27,7 @@ beanie migrate -uri 'mongodb+srv://user:pass@host/db' -p relative/path/to/migrat
 To roll all forward migrations, run:
 
 ```shell
-beanie migrate -uri 'mongodb+srv://user:pass@host/db' -p relative/path/to/migrations/directory/
+beanie migrate -uri 'mongodb://user:pass@host' -db db -p relative/path/to/migrations/directory/
 ```
 
 To roll one backward migration, run:

tests/migrations/test_free_fall.py

@@ -65,3 +65,26 @@ async def test_migration_free_fall(settings, notes, db):
     assert inspection.status == InspectionStatuses.OK
     note = await OldNote.find_one({})
     assert note.name == "0"
+
+
+async def test_migration_free_fall_no_use_transactions(settings, notes, db):
+    migration_settings = MigrationSettings(
+        connection_uri=settings.mongodb_dsn,
+        database_name=settings.mongodb_db_name,
+        path="tests/migrations/migrations_for_test/free_fall",
+        use_transaction=False,
+    )
+    await run_migrate(migration_settings)
+
+    await init_beanie(database=db, document_models=[Note])
+    inspection = await Note.inspect_collection()
+    assert inspection.status == InspectionStatuses.OK
+    note = await Note.find_one({})
+    assert note.title == "0"
+
+    migration_settings.direction = RunningDirections.BACKWARD
+    await run_migrate(migration_settings)
+    inspection = await OldNote.inspect_collection()
+    assert inspection.status == InspectionStatuses.OK
+    note = await OldNote.find_one({})
+    assert note.name == "0"