id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
27403	Document that prefetch_related doesn't guarantee transactional consistency	Aymeric Augustin	Tim Bell	"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."	Cleanup/optimization	closed	Documentation	dev	Normal	fixed		Shai Berger	Ready for checkin	1	0	0	0	0	0