---
title: "データベースのトランザクション"
version: 3.2
locale: ja
source: https://docs.djangoproject.com/ja/3.2/topics/db/transactions/
canonical: https://djangodocs.dev/ja/3.2/topics/db/transactions/
---
# データベースのトランザクション

Django では、データベースのトランザクションをコントロールする方法が提供されています。

## データベースのトランザクションを管理する

### Django のデフォルトのトランザクションの動作

Django のデフォルトの動作は、オートコミットモードで実行することです。トランザクションがアクティブでない限り、各クエリは即座にデータベースにコミットされます。[詳しくは下記を参照してください](#autocommit-details)。

Django は、自動的にトランザクションやセーブポイントを使い、特に [delete()](/ja/3.2/topics/db/queries/#topics-db-queries-delete) と [update()](/ja/3.2/topics/db/queries/#topics-db-queries-update) クエリにおいて、複数のクエリを要求する ORM 操作の信頼性を担保します。

Django の [`TestCase`](/ja/3.2/topics/testing/tools/#django.test.TestCase) クラスは、パフォーマンス向上のため、各テストをトランザクションでラップします。

### HTTP リクエストにトランザクションを結びつける

ウェブ上でトランザクションを扱う一般的な方法は、各リクエストをトランザクションでラップすることです。この動作を有効化したい各データベースの設定で、[`ATOMIC_REQUESTS`](/ja/3.2/ref/settings/#std-setting-DATABASE-ATOMIC_REQUESTS) を `True` にセットしてください。

これは、次のように動作します。まず、ビュー関数を呼び出す前に、Django はトランザクションを開始します。レスポンスが問題なく生成された場合は、Django はトランザクションをコミットします。もしビューが例外を生成した場合は、Django はトランザクションをロールバックします。

ビューのコード (通常は [`atomic()`](#django.db.transaction.atomic) コンテキストマネージャー) の中で、セーブポイントを使ったサブトランザクションを扱うことができます。ただし、ビューの最後では、すべての変更がコミットされるか、何もコミットされないかのどちらかです。

> **Warning**
>
> このトランザクションモデルは簡潔ではありますが、トラフィックが増加するときには非効率となります。全てのビューでトランザクションを扱うとオーバーヘッドが増加します。パフォーマンスへの影響は、アプリケーションのクエリパターンと、どれだけうまくデータベースがロッキングを扱うかに依存します。

> **リクエストごとのトランザクションとストリーミングレスポンス**
>
> ビューが [`StreamingHttpResponse`](/ja/3.2/ref/request-response/#django.http.StreamingHttpResponse) を返すとき、レスポンスの内容読み出しが内容を生成するためのコードを実行することがあります。ビューはすでに返されているので、このコードはトランザクションの外で走ります。
>
> 一般的に言って、ストリーミングレスポンスが生成されている間はデータベースに書き込みすることは推奨されません。レスポンスを送信開始した後にエラーを扱う適切な方法が存在しないからです。

In practice, this feature wraps every view function in the [`atomic()`](#django.db.transaction.atomic)
decorator described below.

あなたのビューの実行だけがトランザクションで閉じられることに注意してください。ミドルウェアはトランザクションの外で実行し、テンプレートレスポンスのレンダリングを実行します。

[`ATOMIC_REQUESTS`](/ja/3.2/ref/settings/#std-setting-DATABASE-ATOMIC_REQUESTS) が有効な場合、ビューがトランザクション内で実行するのを防ぐことができます。

#### `non_atomic_requests(using=None)`

このデコレータは、与えられたビューのために [`ATOMIC_REQUESTS`](/ja/3.2/ref/settings/#std-setting-DATABASE-ATOMIC_REQUESTS) を無効化します。

```
from django.db import transaction

@transaction.non_atomic_requests
def my_view(request):
    do_stuff()

@transaction.non_atomic_requests(using='other')
def my_other_view(request):
    do_stuff_on_the_other_database()
```

ビュー自身に適用される場合にのみ作動します。

### 明示的にトランザクションをコントロールする

Django は、データベーストランザクションをコントロールするための一つの API を提供しています。

#### `atomic(using=None, savepoint=True, durable=False)`

Atomicityは、データベーストランザクションの定義プロパティです。`atomic` は、データベースの atomicity が保証されるコードブロックを作成することを可能にします。 コードブロックが正常に完了すると、変更はデータベースにコミットされます。 例外がある場合、変更はロールバックされます。

`atomic` のブロックはネスト可能です。この場合、内側のブロックが成功裏に完了しても、その効果は後で外側のブロックで例外が発生した場合にロールバック可能となっています。

It is sometimes useful to ensure an `atomic` block is always the
outermost `atomic` block, ensuring that any database changes are
committed when the block is exited without errors. This is known as
durability and can be achieved by setting `durable=True`. If the
`atomic` block is nested within another it raises a `RuntimeError`.

`atomic` は、[decorator](https://docs.python.org/3/glossary.html#term-decorator) として使用することも:

```
from django.db import transaction

@transaction.atomic
def viewfunc(request):
    # This code executes inside a transaction.
    do_stuff()
```

[context manager](https://docs.python.org/3/glossary.html#term-context-manager) として使用することも可能です:

```
from django.db import transaction

def viewfunc(request):
    # This code executes in autocommit mode (Django's default).
    do_stuff()

    with transaction.atomic():
        # This code executes inside a transaction.
        do_more_stuff()
```

try/except ブロック内で `atomic` をラップすると、integrity error を自然な形で処理できます:

```
from django.db import IntegrityError, transaction

@transaction.atomic
def viewfunc(request):
    create_parent()

    try:
        with transaction.atomic():
            generate_relationships()
    except IntegrityError:
        handle_exception()

    add_children()
```

In this example, even if `generate_relationships()` causes a database
error by breaking an integrity constraint, you can execute queries in
`add_children()`, and the changes from `create_parent()` are still
there and bound to the same transaction. Note that any operations attempted
in `generate_relationships()` will already have been rolled back safely
when `handle_exception()` is called, so the exception handler can also
operate on the database if necessary.

> **atomic の内部で例外をキャッチしない!**
>
> `atomic` ブロックの処理を終える際、Django は通常の終了なのか例外を伴うのかを見て、コミットするかロールバックするかを決定します。`atomic` ブロック内で例外をキャッチしてハンドする場合、Django に対して問題が発生したことを隠すことになります。これは予期しない動作の原因となります。
>
> この挙動は、[`DatabaseError`](/ja/3.2/ref/exceptions/#django.db.DatabaseError) およびそのサブクラス　([`IntegrityError`](/ja/3.2/ref/exceptions/#django.db.IntegrityError) など) に対する懸念となります。こうしたエラーが起きた場合、Djangoは `atomic` ブロックの最後にロー路バックを実施します。ロールバックが発生する前にデータベースクエリを実行しようとすると、Django は [`TransactionManagementError`](/ja/3.2/ref/exceptions/#django.db.transaction.TransactionManagementError) を送出します。ORM 関連のシグナルハンドラが例外を送出した際にも同様の挙動となります。
>
> データベースエラーをキャッチする正しい方法は、上記で示した通りの `atomic` ブロックです。必要に応じてさらに `atomic` ブロックを追加してください。このパターンはもう一つのメリットがあります: 例外が発生した場合にどの操作がロールバックされるかを限定できることです。
>
> 素の SQL クエリによって発生した例外をキャッチした場合、Django の挙動は決まっておらず、データベースに依存します。

> **You may need to manually revert model state when rolling back a transaction.**
>
> The values of a model's fields won't be reverted when a transaction
> rollback happens. This could lead to an inconsistent model state unless
> you manually restore the original field values.
>
> For example, given `MyModel` with an `active` field, this snippet
> ensures that the `if obj.active` check at the end uses the correct
> value if updating `active` to `True` fails in the transaction:
>
> ```
> from django.db import DatabaseError, transaction
>
> obj = MyModel(active=False)
> obj.active = True
> try:
>     with transaction.atomic():
>         obj.save()
> except DatabaseError:
>     obj.active = False
>
> if obj.active:
>     ...
> ```

In order to guarantee atomicity, `atomic` disables some APIs. Attempting
to commit, roll back, or change the autocommit state of the database
connection within an `atomic` block will raise an exception.

`atomic` takes a `using` argument which should be the name of a
database. If this argument isn't provided, Django uses the `"default"`
database.

Under the hood, Django's transaction management code:

- opens a transaction when entering the outermost `atomic` block;
- creates a savepoint when entering an inner `atomic` block;
- releases or rolls back to the savepoint when exiting an inner block;
- commits or rolls back the transaction when exiting the outermost block.

You can disable the creation of savepoints for inner blocks by setting the
`savepoint` argument to `False`. If an exception occurs, Django will
perform the rollback when exiting the first parent block with a savepoint
if there is one, and the outermost block otherwise. Atomicity is still
guaranteed by the outer transaction. This option should only be used if
the overhead of savepoints is noticeable. It has the drawback of breaking
the error handling described above.

You may use `atomic` when autocommit is turned off. It will only use
savepoints, even for the outermost block.

> **Performance considerations**
>
> Open transactions have a performance cost for your database server. To
> minimize this overhead, keep your transactions as short as possible. This
> is especially important if you're using [`atomic()`](#django.db.transaction.atomic) in long-running
> processes, outside of Django's request / response cycle.

> **Warning**
>
> [`django.test.TestCase`](/ja/3.2/topics/testing/tools/#django.test.TestCase) disables the durability check to allow
> testing durable atomic blocks in a transaction for performance reasons. Use
> [`django.test.TransactionTestCase`](/ja/3.2/topics/testing/tools/#django.test.TransactionTestCase) for testing durability.

> **Changed in Django 3.2**
>
> The `durable` argument was added.

## 自動コミット

### なぜ Django は自動コミットを使うのか

In the SQL standards, each SQL query starts a transaction, unless one is
already active. Such transactions must then be explicitly committed or rolled
back.

This isn't always convenient for application developers. To alleviate this
problem, most databases provide an autocommit mode. When autocommit is turned
on and no transaction is active, each SQL query gets wrapped in its own
transaction. In other words, not only does each such query start a
transaction, but the transaction also gets automatically committed or rolled
back, depending on whether the query succeeded.

[**PEP 249**](https://peps.python.org/pep-0249/), the Python Database API Specification v2.0, requires autocommit to
be initially turned off. Django overrides this default and turns autocommit
on.

To avoid this, you can [deactivate the transaction management](#deactivate-transaction-management), but it isn't recommended.

### Deactivating transaction management

You can totally disable Django's transaction management for a given database
by setting [`AUTOCOMMIT`](/ja/3.2/ref/settings/#std-setting-DATABASE-AUTOCOMMIT) to `False` in its
configuration. If you do this, Django won't enable autocommit, and won't
perform any commits. You'll get the regular behavior of the underlying
database library.

This requires you to commit explicitly every transaction, even those started
by Django or by third-party libraries. Thus, this is best used in situations
where you want to run your own transaction-controlling middleware or do
something really strange.

## Performing actions after commit

Sometimes you need to perform an action related to the current database
transaction, but only if the transaction successfully commits. Examples might
include a [Celery](https://pypi.org/project/celery/) task, an email notification, or a cache invalidation.

Django provides the [`on_commit()`](#django.db.transaction.on_commit) function to register callback functions
that should be executed after a transaction is successfully committed:

#### `on_commit(func, using=None)`

Pass any function (that takes no arguments) to [`on_commit()`](#django.db.transaction.on_commit):

```
from django.db import transaction

def do_something():
    pass  # send a mail, invalidate a cache, fire off a Celery task, etc.

transaction.on_commit(do_something)
```

You can also wrap your function in a lambda:

```
transaction.on_commit(lambda: some_celery_task.delay('arg1'))
```

The function you pass in will be called immediately after a hypothetical
database write made where `on_commit()` is called would be successfully
committed.

If you call `on_commit()` while there isn't an active transaction, the
callback will be executed immediately.

If that hypothetical database write is instead rolled back (typically when an
unhandled exception is raised in an [`atomic()`](#django.db.transaction.atomic) block), your function will
be discarded and never called.

### Savepoints

Savepoints (i.e. nested [`atomic()`](#django.db.transaction.atomic) blocks) are handled correctly. That is,
an [`on_commit()`](#django.db.transaction.on_commit) callable registered after a savepoint (in a nested
[`atomic()`](#django.db.transaction.atomic) block) will be called after the outer transaction is committed,
but not if a rollback to that savepoint or any previous savepoint occurred
during the transaction:

```
with transaction.atomic():  # Outer atomic, start a new transaction
    transaction.on_commit(foo)

    with transaction.atomic():  # Inner atomic block, create a savepoint
        transaction.on_commit(bar)

# foo() and then bar() will be called when leaving the outermost block
```

On the other hand, when a savepoint is rolled back (due to an exception being
raised), the inner callable will not be called:

```
with transaction.atomic():  # Outer atomic, start a new transaction
    transaction.on_commit(foo)

    try:
        with transaction.atomic():  # Inner atomic block, create a savepoint
            transaction.on_commit(bar)
            raise SomeError()  # Raising an exception - abort the savepoint
    except SomeError:
        pass

# foo() will be called, but not bar()
```

### Order of execution

On-commit functions for a given transaction are executed in the order they were
registered.

### Exception handling

If one on-commit function within a given transaction raises an uncaught
exception, no later registered functions in that same transaction will run.
This is the same behavior as if you'd executed the functions sequentially
yourself without [`on_commit()`](#django.db.transaction.on_commit).

### Timing of execution

Your callbacks are executed *after* a successful commit, so a failure in a
callback will not cause the transaction to roll back. They are executed
conditionally upon the success of the transaction, but they are not *part* of
the transaction. For the intended use cases (mail notifications, Celery tasks,
etc.), this should be fine. If it's not (if your follow-up action is so
critical that its failure should mean the failure of the transaction itself),
then you don't want to use the [`on_commit()`](#django.db.transaction.on_commit) hook. Instead, you may want
[two-phase commit](https://en.wikipedia.org/wiki/Two-phase_commit_protocol) such as the [psycopg Two-Phase Commit protocol support](https://www.psycopg.org/docs/usage.html#tpc) and the [**optional Two-Phase Commit Extensions in the
Python DB-API specification**](https://peps.python.org/pep-0249/#optional-two-phase-commit-extensions).

Callbacks are not run until autocommit is restored on the connection following
the commit (because otherwise any queries done in a callback would open an
implicit transaction, preventing the connection from going back into autocommit
mode).

When in autocommit mode and outside of an [`atomic()`](#django.db.transaction.atomic) block, the function
will run immediately, not on commit.

On-commit functions only work with [autocommit mode](#managing-autocommit)
and the [`atomic()`](#django.db.transaction.atomic) (or [`ATOMIC_REQUESTS`](/ja/3.2/ref/settings/#std-setting-DATABASE-ATOMIC_REQUESTS)) transaction API. Calling [`on_commit()`](#django.db.transaction.on_commit) when
autocommit is disabled and you are not within an atomic block will result in an
error.

### Use in tests

Django's [`TestCase`](/ja/3.2/topics/testing/tools/#django.test.TestCase) class wraps each test in a transaction
and rolls back that transaction after each test, in order to provide test
isolation. This means that no transaction is ever actually committed, thus your
[`on_commit()`](#django.db.transaction.on_commit) callbacks will never be run.

You can overcome this limitation by using
[`TestCase.captureOnCommitCallbacks()`](/ja/3.2/topics/testing/tools/#django.test.TestCase.captureOnCommitCallbacks). This captures your
[`on_commit()`](#django.db.transaction.on_commit) callbacks in a list, allowing you to make assertions on them,
or emulate the transaction committing by calling them.

Another way to overcome the limitation is to use
[`TransactionTestCase`](/ja/3.2/topics/testing/tools/#django.test.TransactionTestCase) instead of
[`TestCase`](/ja/3.2/topics/testing/tools/#django.test.TestCase). This will mean your transactions are committed,
and the callbacks will run. However
[`TransactionTestCase`](/ja/3.2/topics/testing/tools/#django.test.TransactionTestCase) flushes the database between tests,
which is significantly slower than [`TestCase`](/ja/3.2/topics/testing/tools/#django.test.TestCase)'s isolation.

### Why no rollback hook?

A rollback hook is harder to implement robustly than a commit hook, since a
variety of things can cause an implicit rollback.

For instance, if your database connection is dropped because your process was
killed without a chance to shut down gracefully, your rollback hook will never
run.

But there is a solution: instead of doing something during the atomic block
(transaction) and then undoing it if the transaction fails, use
[`on_commit()`](#django.db.transaction.on_commit) to delay doing it in the first place until after the
transaction succeeds. It's a lot easier to undo something you never did in the
first place!

## Low-level APIs

> **Warning**
>
> Always prefer [`atomic()`](#django.db.transaction.atomic) if possible at all. It accounts for the
> idiosyncrasies of each database and prevents invalid operations.
>
> The low level APIs are only useful if you're implementing your own
> transaction management.

### 自動コミット

Django provides an API in the [`django.db.transaction`](#module-django.db.transaction) module to manage the
autocommit state of each database connection.

#### `get_autocommit(using=None)`

#### `set_autocommit(autocommit, using=None)`

These functions take a `using` argument which should be the name of a
database. If it isn't provided, Django uses the `"default"` database.

Autocommit is initially turned on. If you turn it off, it's your
responsibility to restore it.

Once you turn autocommit off, you get the default behavior of your database
adapter, and Django won't help you. Although that behavior is specified in
[**PEP 249**](https://peps.python.org/pep-0249/), implementations of adapters aren't always consistent with one
another. Review the documentation of the adapter you're using carefully.

You must ensure that no transaction is active, usually by issuing a
[`commit()`](#django.db.transaction.commit) or a [`rollback()`](#django.db.transaction.rollback), before turning autocommit back on.

Django will refuse to turn autocommit off when an [`atomic()`](#django.db.transaction.atomic) block is
active, because that would break atomicity.

### Transactions

A transaction is an atomic set of database queries. Even if your program
crashes, the database guarantees that either all the changes will be applied,
or none of them.

Django doesn't provide an API to start a transaction. The expected way to
start a transaction is to disable autocommit with [`set_autocommit()`](#django.db.transaction.set_autocommit).

Once you're in a transaction, you can choose either to apply the changes
you've performed until this point with [`commit()`](#django.db.transaction.commit), or to cancel them with
[`rollback()`](#django.db.transaction.rollback). These functions are defined in [`django.db.transaction`](#module-django.db.transaction).

#### `commit(using=None)`

#### `rollback(using=None)`

These functions take a `using` argument which should be the name of a
database. If it isn't provided, Django uses the `"default"` database.

Django will refuse to commit or to rollback when an [`atomic()`](#django.db.transaction.atomic) block is
active, because that would break atomicity.

### Savepoints

A savepoint is a marker within a transaction that enables you to roll back
part of a transaction, rather than the full transaction. Savepoints are
available with the SQLite, PostgreSQL, Oracle, and MySQL (when using the InnoDB
storage engine) backends. Other backends provide the savepoint functions, but
they're empty operations -- they don't actually do anything.

Savepoints aren't especially useful if you are using autocommit, the default
behavior of Django. However, once you open a transaction with [`atomic()`](#django.db.transaction.atomic),
you build up a series of database operations awaiting a commit or rollback. If
you issue a rollback, the entire transaction is rolled back. Savepoints
provide the ability to perform a fine-grained rollback, rather than the full
rollback that would be performed by `transaction.rollback()`.

When the [`atomic()`](#django.db.transaction.atomic) decorator is nested, it creates a savepoint to allow
partial commit or rollback. You're strongly encouraged to use [`atomic()`](#django.db.transaction.atomic)
rather than the functions described below, but they're still part of the
public API, and there's no plan to deprecate them.

Each of these functions takes a `using` argument which should be the name of
a database for which the behavior applies.  If no `using` argument is
provided then the `"default"` database is used.

Savepoints are controlled by three functions in [`django.db.transaction`](#module-django.db.transaction):

#### `savepoint(using=None)`

Creates a new savepoint. This marks a point in the transaction that is
known to be in a "good" state. Returns the savepoint ID (`sid`).

#### `savepoint_commit(sid, using=None)`

Releases savepoint `sid`. The changes performed since the savepoint was
created become part of the transaction.

#### `savepoint_rollback(sid, using=None)`

Rolls back the transaction to savepoint `sid`.

These functions do nothing if savepoints aren't supported or if the database
is in autocommit mode.

In addition, there's a utility function:

#### `clean_savepoints(using=None)`

Resets the counter used to generate unique savepoint IDs.

The following example demonstrates the use of savepoints:

```
from django.db import transaction

# open a transaction
@transaction.atomic
def viewfunc(request):

    a.save()
    # transaction now contains a.save()

    sid = transaction.savepoint()

    b.save()
    # transaction now contains a.save() and b.save()

    if want_to_keep_b:
        transaction.savepoint_commit(sid)
        # open transaction still contains a.save() and b.save()
    else:
        transaction.savepoint_rollback(sid)
        # open transaction now contains only a.save()
```

Savepoints may be used to recover from a database error by performing a partial
rollback. If you're doing this inside an [`atomic()`](#django.db.transaction.atomic) block, the entire block
will still be rolled back, because it doesn't know you've handled the situation
at a lower level! To prevent this, you can control the rollback behavior with
the following functions.

#### `get_rollback(using=None)`

#### `set_rollback(rollback, using=None)`

Setting the rollback flag to `True` forces a rollback when exiting the
innermost atomic block. This may be useful to trigger a rollback without
raising an exception.

Setting it to `False` prevents such a rollback. Before doing that, make sure
you've rolled back the transaction to a known-good savepoint within the current
atomic block! Otherwise you're breaking atomicity and data corruption may
occur.

## Database-specific notes

### Savepoints in SQLite

While SQLite supports savepoints, a flaw in the design of the [`sqlite3`](https://docs.python.org/3/library/sqlite3.html#module-sqlite3)
module makes them hardly usable.

When autocommit is enabled, savepoints don't make sense. When it's disabled,
[`sqlite3`](https://docs.python.org/3/library/sqlite3.html#module-sqlite3) commits implicitly before savepoint statements. (In fact, it
commits before any statement other than `SELECT`, `INSERT`, `UPDATE`,
`DELETE` and `REPLACE`.) This bug has two consequences:

- The low level APIs for savepoints are only usable inside a transaction ie.
  inside an [`atomic()`](#django.db.transaction.atomic) block.
- It's impossible to use [`atomic()`](#django.db.transaction.atomic) when autocommit is turned off.

### Transactions in MySQL

If you're using MySQL, your tables may or may not support transactions; it
depends on your MySQL version and the table types you're using. (By
"table types," we mean something like "InnoDB" or "MyISAM".) MySQL transaction
peculiarities are outside the scope of this article, but the MySQL site has
[information on MySQL transactions](https://dev.mysql.com/doc/refman/en/sql-transactional-statements.html).

If your MySQL setup does *not* support transactions, then Django will always
function in autocommit mode: statements will be executed and committed as soon
as they're called. If your MySQL setup *does* support transactions, Django
will handle transactions as explained in this document.

### Handling exceptions within PostgreSQL transactions

> **Note**
>
> This section is relevant only if you're implementing your own transaction
> management. This problem cannot occur in Django's default mode and
> [`atomic()`](#django.db.transaction.atomic) handles it automatically.

Inside a transaction, when a call to a PostgreSQL cursor raises an exception
(typically `IntegrityError`), all subsequent SQL in the same transaction
will fail with the error "current transaction is aborted, queries ignored
until end of transaction block". While the basic use of `save()` is unlikely
to raise an exception in PostgreSQL, there are more advanced usage patterns
which might, such as saving objects with unique fields, saving using the
force\_insert/force\_update flag, or invoking custom SQL.

There are several ways to recover from this sort of error.

#### Transaction rollback

The first option is to roll back the entire transaction. For example:

```
a.save() # Succeeds, but may be undone by transaction rollback
try:
    b.save() # Could throw exception
except IntegrityError:
    transaction.rollback()
c.save() # Succeeds, but a.save() may have been undone
```

Calling `transaction.rollback()` rolls back the entire transaction. Any
uncommitted database operations will be lost. In this example, the changes
made by `a.save()` would be lost, even though that operation raised no error
itself.

#### Savepoint rollback

You can use [savepoints](#topics-db-transactions-savepoints) to control
the extent of a rollback. Before performing a database operation that could
fail, you can set or update the savepoint; that way, if the operation fails,
you can roll back the single offending operation, rather than the entire
transaction. For example:

```
a.save() # Succeeds, and never undone by savepoint rollback
sid = transaction.savepoint()
try:
    b.save() # Could throw exception
    transaction.savepoint_commit(sid)
except IntegrityError:
    transaction.savepoint_rollback(sid)
c.save() # Succeeds, and a.save() is never undone
```

In this example, `a.save()` will not be undone in the case where
`b.save()` raises an exception.