Opened 6 years ago
Last modified 4 years ago
#29078 closed Cleanup/optimization
Serializer handle_m2m_field should honour any previous prefetch — at Initial Version
| Reported by: | xx396 | Owned by: | nobody |
|---|---|---|---|
| Component: | Core (Serialization) | Version: | 2.0 |
| Severity: | Normal | Keywords: | |
| Cc: | Triage Stage: | Accepted | |
| Has patch: | yes | Needs documentation: | no |
| Needs tests: | no | Patch needs improvement: | no |
| Easy pickings: | no | UI/UX: | no |
Description
Example:
from django.contrib.auth.models import Group
from django.core import serializers
groups = Group.objects.prefetch_related('permissionscontent_type').all()
serializers.serialize('json', groups)
This will N+1 query the permissions as handle_m2m_field uses iterator() which bypasses any cache. Suggest serializers/python.py line 77 replaces iterator() with all()
self._current[field.name] = [
m2m_value(related) for related in getattr(obj, field.name).iterator()
]
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