#17014: prefetch_related infinite recursion by default managers
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Reporter: akaariai | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.3
(models, ORM) | Resolution:
Severity: Normal | Triage Stage:
Keywords: | Unreviewed
Has patch: 0 | Needs documentation: 1
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Changes (by akaariai):
* cc: anssi.kaariainen@… (added)
* needs_better_patch: => 0
* needs_docs: => 1
* needs_tests: => 0
Comment:
Ok, I have confirmed this against both #17003 patch and trunk. Recursion
will eat all your memory and OOM killer will get into action (after some
trashing). The attached test cases show the problem. I think the patch
will apply to #17003, too.
I will work on a patch against trunk next. My idea is to track added
prefetches by key (model, to_attr) where to_attr will be currently the
name of the related manager we are caching the results in. If we are
adding a prefetch related lookup into the query and the lookup came from
default manager, we will bail out. This way it is possible to traverse the
same path intentionally, but default manager recursion will be avoided.
That is, we can define that we want People -> friends -> friends, but if
we have default prefetch for friends, we will bail out because lookup
People -> friends has been added to the query already. I will try to do
one against #17003, too.
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Ticket URL: <https://code.djangoproject.com/ticket/17014#comment:1>
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