https://github.com/ambitioneng/django-pgtransaction
A context manager/decorator which extends Django's atomic function with the ability to set isolation level and retries for a given transaction.
https://github.com/ambitioneng/django-pgtransaction
django postgresql transactions
Last synced: 4 months ago
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A context manager/decorator which extends Django's atomic function with the ability to set isolation level and retries for a given transaction.
- Host: GitHub
- URL: https://github.com/ambitioneng/django-pgtransaction
- Owner: AmbitionEng
- License: bsd-3-clause
- Created: 2022-09-14T14:52:26.000Z (about 3 years ago)
- Default Branch: main
- Last Pushed: 2025-05-28T09:43:21.000Z (5 months ago)
- Last Synced: 2025-06-06T02:06:39.765Z (4 months ago)
- Topics: django, postgresql, transactions
- Language: Python
- Homepage: https://django-pgtransaction.readthedocs.io
- Size: 271 KB
- Stars: 59
- Watchers: 3
- Forks: 3
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
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README
# django-pgtransaction
django-pgtransaction offers a drop-in replacement for the default `django.db.transaction` module which, when used on top of a PostgreSQL database, extends the functionality of that module with Postgres-specific features.
At present, django-pgtransaction offers an extension of the `django.db.transaction.atomic` context manager/decorator which allows one to dynamically set [transaction characteristics](https://www.postgresql.org/docs/current/sql-set-transaction.html) including:
- [Isolation level](https://www.postgresql.org/docs/current/transaction-iso.html)
- Read mode (READ WRITE/READ ONLY)
- Deferrability (DEFERRABLE/NOT DEFERRABLE)
- Retry policy for Postgres locking exceptions
See the quickstart below or [the docs](https://django-pgtransaction.readthedocs.io/) for examples.
## Quickstart
After installation, set transaction characteristics using `pgtransaction.atomic`:
### Isolation Levels
Set the isolation level for specific consistency guarantees:
```python
import pgtransaction
with pgtransaction.atomic(isolation_level=pgtransaction.SERIALIZABLE):
# Do queries with SERIALIZABLE isolation...
```
There are three isolation levels: `pgtransaction.READ_COMMITTED`, `pgtransaction.REPEATABLE_READ`, and `pgtransaction.SERIALIZABLE`. By default it inherits the parent isolation level, which is Django's default of "READ COMMITTED".
### Read-Only Transactions
Read-only mode can be used queries that don't modify data:
```python
with pgtransaction.atomic(read_mode=pgtransaction.READ_ONLY):
# Can only read, not write
results = MyModel.objects.all()
```
### Deferrable Transactions
Prevent serialization failures for long-running queries by blocking:
```python
with pgtransaction.atomic(
isolation_level=pgtransaction.SERIALIZABLE,
read_mode=pgtransaction.READ_ONLY,
deferrable=pgtransaction.DEFERRABLE
):
# Long-running read-only query that won't cause serialization conflicts
analytics_data = expensive_query()
```
Note: `DEFERRABLE` only works with `SERIALIZABLE` isolation level and `READ_ONLY` mode.
### Retries for Concurrent Updates
When using stricter isolation levels like `pgtransaction.SERIALIZABLE`, Postgres will throw serialization errors upon concurrent updates to rows. Use the `retry` argument with the decorator to retry these failures:
```python
@pgtransaction.atomic(isolation_level=pgtransaction.SERIALIZABLE, retry=3)
def do_queries():
# Do queries...
```
Note that the `retry` argument will not work when used as a context manager. A `RuntimeError` will be thrown.
By default, retries are only performed when `psycopg.errors.SerializationError` or `psycopg.errors.DeadlockDetected` errors are raised. Configure retried psycopg errors with `settings.PGTRANSACTION_RETRY_EXCEPTIONS`. You can set a default retry amount with `settings.PGTRANSACTION_RETRY`.
### Nested Usage
`pgtransaction.atomic` can be nested, but keep the following in mind:
1. Isolation mode cannot be changed once a query has been performed.
2. Read-write mode can not be changed to from within a read only block.
3. The retry argument only works on the outermost invocation as a decorator, otherwise `RuntimeError` is raised.
## Compatibility
`django-pgtransaction` is compatible with Python 3.9 - 3.13, Django 4.2 - 5.1, Psycopg 2 - 3, and Postgres 13 - 17.
## Documentation
Check out the [Postgres docs](https://www.postgresql.org/docs/current/transaction-iso.html) to learn about transaction isolation in Postgres.
[View the django-pgtransaction docs here](https://django-pgtransaction.readthedocs.io/)
## Installation
Install `django-pgtransaction` with:
pip3 install django-pgtransaction
After this, add `pgtransaction` to the `INSTALLED_APPS` setting of your Django project.
## Contributing Guide
For information on setting up django-pgtransaction for development and contributing changes, view [CONTRIBUTING.md](CONTRIBUTING.md).
## Creators
- [Paul Gilmartin](https://github.com/PaulGilmartin)
- [Wes Kendall](https://github.com/wesleykendall)