CODEWITHSUNDEEP
djangopostgresqlcelery
ketanbhatt
ketanbhatt

Reputation: 988

"select_for_update" called from an atomic block still TransactionManagementError

I am working with django on a large project.

I call a celery task from inside the save of a model that calls a method which calls another method in a loop. That is:

celery task --> function A()
A() --> for i in range(1,100): call function B()

Now B() is wrapped with an atomic() decorator and has a select_for_update call inside it.

I still get TransactionManagementError('select_for_update cannot be used outside of a transaction.',)

I do not know why this is. I have tested with delaying the task by a few seconds so that the save is committed by the time the task is called. Did not help.

My question is: Why am I getting a TransactionManagementError when I am already inside an atomic block?

Upvotes: 4

Views: 1977

Answers (1)

Vikas Gulati
Vikas Gulati

Reputation: 998

@ketanbhatt This might help

https://docs.djangoproject.com/en/1.9/ref/models/querysets/#select-for-update

Evaluating a queryset with select_for_update() in autocommit mode on backends which support SELECT ... FOR UPDATE is a TransactionManagementError error because the rows are not locked in that case. If allowed, this would facilitate data corruption and could easily be caused by calling code that expects to be run in a transaction outside of one.

https://docs.djangoproject.com/en/1.9/topics/db/transactions/#managing-autocommit

Django will refuse to turn autocommit off when an atomic() block is active, because that would break atomicity.

Upvotes: 2

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