#27403: prefetch_related doesn't guarantee transactional consistency
-------------------------------------+-------------------------------------
Reporter: Aymeric | Owner: nobody
Augustin |
Type: Bug | Status: new
Component: Database | Version: master
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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Let's assume a `Parent` model and a `Child` model with a FK to `Parent`.
Database initially looks like this:
{{{
parent1 -- child1
}}}
User runs `Parent.objects.all().prefetch_related('child_set')`.
Django fetches `parent1`.
Another transaction commits, resulting in this structure:
{{{
parent1 +- child1
`- child2
parent2
}}}
Django fetches all children pointing to `parent1`, which returns `child1`
and `child2`.
The result of the query is:
{{{
parent1 +- child1
`- child2
}}}
But at no point in the history did the database look like this.
This bug report is based on code inspection.
I verified that `prefetch_related` doesn't start a transaction.
However I didn't write code exhibiting the race condition because that's a
bit complicated.
--
Ticket URL: <https://code.djangoproject.com/ticket/27403>
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