Opened 9 years ago
Closed 9 years ago
#26515 closed Bug (fixed)
trim_joins bug with nested related models using ForeignObject
Reported by: | darius | Owned by: | nobody |
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Component: | Database layer (models, ORM) | Version: | 1.9 |
Severity: | Normal | Keywords: | ForeignObject, trim_join, orm |
Cc: | Triage Stage: | Accepted | |
Has patch: | yes | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description
the order in which we declare the from_fields
and to_fields
does matter if we make a nested lookup.
it is clear that the fields in from_fields and to_fields must be on the same orders, but if 3 models use ForeignObject to links themselves, and the fields are the sames on all 3 models, the order in which they are declared in both fields must be the same.
a example app that can trigger the bug follow :
class Address(models.Model): company = models.CharField(max_length=1) tiers_id = models.IntegerField() city = models.CharField(max_length=255) postcode = models.CharField(max_length=32) class Meta(object): unique_together = [ ("company", "tiers_id"), ] class Customer(models.Model): company = models.CharField(max_length=1) customer_id = models.IntegerField() name = models.CharField(max_length=255) address = ForeignObject( Address, on_delete=CASCADE, null=True, from_fields=["customer_id", "company"], to_fields=["tiers_id", "company"] ) class Meta(object): unique_together = [ ("company", "customer_id"), ] class Contact(models.Model): company_code = models.CharField(max_length=1) customer_code = models.IntegerField() surname = models.CharField(max_length=255) # virtual field customer = ForeignObject( Customer, on_delete=CASCADE, related_name='contacts', # not the same order as for Customer -> address which is (customer, company) to_fields=["company", "customer_id"], from_fields=["company_code", "customer_code"] # with same order as for Customer, the bug does not trigger # to_fields = ["customer_id", "company"], # from_fields = ["customer_code", "company_code"] ) class PhoneNumber(models.Model): num = models.CharField(max_length=32) type_number = models.IntegerField() contact = models.ForeignKey(Contact, on_delete=CASCADE, related_name='phonenumbers')
with this models.py, the different orders of the fields Contact.customer can break all query like PhoneNumber.objects.filter(contact__customer__address=a)
.(see comment in Customer)
I found the problem is in django.db.models.query.Query.trim_joins line 1444 on release 1.9.5
targets = tuple(r[0] for r in info.join_field.related_fields if r[1].column in cur_targets)
we see that the new targets is created using the previous used targets, but the order of the previous target is not kept, and the order of to_fields is used to define the new targets.
this lead to a query like :
SELECT "buggyapp_phonenumber"."id", "buggyapp_phonenumber"."num", "buggyapp_phonenumber"."type_number", "buggyapp_phonenumber"."contact_id" FROM "buggyapp_phonenumber" INNER JOIN "buggyapp_contact" ON ("buggyapp_phonenumber"."contact_id" = "buggyapp_contact"."id") WHERE ("buggyapp_contact"."company_code" = 10 AND "buggyapp_contact"."customer_code" = a)
instead of
SELECT "buggyapp_phonenumber"."id", "buggyapp_phonenumber"."num", "buggyapp_phonenumber"."type_number", "buggyapp_phonenumber"."contact_id" FROM "buggyapp_phonenumber" INNER JOIN "buggyapp_contact" ON ("buggyapp_phonenumber"."contact_id" = "buggyapp_contact"."id") WHERE ("buggyapp_contact"."customer_code" = 10 AND "buggyapp_contact"."company_code" = a)
the where part have the values order kept, but the fields order is inconsistent and it end with customer_code = 'a' instead of 10.
the attached files contains a basic app that trigger the bug, and a patch in trim_query that will build the new targets with same order as the previous.
the patch is made for django 1.9.5
Attachments (2)
Change History (9)
by , 9 years ago
Attachment: | ForeignObject_from_fields__bug_26515.tar.gz added |
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by , 9 years ago
Attachment: | ForeignObject_from_fields__bug_26515.patch added |
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patch that keep order of targets in trim_joins
follow-up: 2 comment:1 by , 9 years ago
Can you create a test for this in Django's test suite? See tests/foreign_object/ directory for some similar tests.
comment:2 by , 9 years ago
Replying to akaariai:
Can you create a test for this in Django's test suite? See tests/foreign_object/ directory for some similar tests.
I just forked the django repo (hope it was what you expected) and wrote down my tests in tests/foreign_object/.
the test test_very_deep_optimized_forward
fail without the patch, and after patch, all tests pass on my computer.
all is on my branch https://github.com/ornoone/django/tree/%2326515_trimjoin_bug
comment:3 by , 9 years ago
Could you please send a pull request against master with those changes? See our PatchReviewChecklist.
comment:5 by , 9 years ago
Patch needs improvement: | set |
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Triage Stage: | Unreviewed → Accepted |
Left comments for cosmetic improvements on the PR.
comment:6 by , 9 years ago
Patch needs improvement: | unset |
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simple app to trigger the bug