From 3d037b9f689d287567d5961939817d96907a1459 Mon Sep 17 00:00:00 2001 From: Simon Charette Date: Wed, 11 Nov 2015 00:40:20 -0500 Subject: [PATCH] [1.7.x] Refs #25693 -- Avoided redundant calls to get_fields() in `to_attr` validation. Conflicts: django/db/models/query.py Backport of cc8c02fa0fa2119704d1c39ca8509850aef84acc from master --- django/db/models/query.py | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/django/db/models/query.py b/django/db/models/query.py index dca6eea1ba..ac68bec0dd 100644 --- a/django/db/models/query.py +++ b/django/db/models/query.py @@ -1906,17 +1906,20 @@ def prefetch_one_level(instances, prefetcher, lookup, level): rel_attr_val = rel_obj_attr(rel_obj) rel_obj_cache.setdefault(rel_attr_val, []).append(rel_obj) + to_attr, as_attr = lookup.get_current_to_attr(level) + # Make sure `to_attr` does not conflict with a field. + if as_attr and instances: + # We assume that objects retrieved are homogeneous (which is the premise + # of prefetch_related), so what applies to first object applies to all. + model = instances[0].__class__ + for related_m2m in model._meta.get_all_related_many_to_many_objects(): + if related_m2m.get_accessor_name() == to_attr: + msg = 'to_attr={} conflicts with a field on the {} model.' + raise ValueError(msg.format(to_attr, model.__name__)) + for obj in instances: instance_attr_val = instance_attr(obj) vals = rel_obj_cache.get(instance_attr_val, []) - to_attr, as_attr = lookup.get_current_to_attr(level) - - # Check we are not shadowing a field on obj. - if as_attr: - for related_m2m in obj._meta.get_all_related_many_to_many_objects(): - if related_m2m.get_accessor_name() == to_attr: - msg = 'to_attr={} conflicts with a field on the {} model.' - raise ValueError(msg.format(to_attr, obj.__class__.__name__)) if single: val = vals[0] if vals else None