Django: how to do get_or_create() in a threadsafe way?

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In my Django app very often I need to do something similar to get_or_create(). E.g.,

User submits a tag. Need to see if that tag already is in the database. If not, create a new record for it. If it is, just update the existing record.

But looking into the doc for get_or_create() it looks like it's not threadsafe. Thread A checks and finds Record X does not exist. Then Thread B checks and finds that Record X does not exist. Now both Thread A and Thread B will create a new Record X.

This must be a very common situation. How do I handle it in a threadsafe way?

thread-safety concurrency django python database
4 Answers

So many years have passed, but nobody has written about threading.Lock. If you don't have the opportunity to make migrations for unique together, for legacy reasons, you can use locks or threading.Semaphore objects. Here is the pseudocode:

from concurrent.futures import ThreadPoolExecutor
from threading import Lock

_lock = Lock()


def get_staff(data: dict):
    _lock.acquire()
    try:
        staff, created = MyModel.objects.get_or_create(**data)
        return staff
    finally:
        _lock.release()


with ThreadPoolExecutor(max_workers=50) as pool:
    pool.map(get_staff, get_list_of_some_data())
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