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Refs #29908 -- Optimized known related objects assignment.

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Since CPython implements a C level attrgetter(*attrs) it even outperforms the
most common case of a single known related object since the resulting attribute
values tuple is built in C.
This commit is contained in:
Simon Charette 2018-11-16 17:23:12 -05:00
parent f436c82637
commit 0cf85e6b07
2 changed files with 19 additions and 13 deletions
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16
django/db/models/query.py
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@ -62,14 +62,12 @@ class ModelIterable(BaseIterable):
for f in select[model_fields_start:model_fields_end]]
related_populators = get_related_populators(klass_info, select, db)
known_related_objects = [
(field, related_objs, [
operator.attrgetter(
field.attname
if from_field == 'self' else
queryset.model._meta.get_field(from_field).attname
)
(field, related_objs, operator.attrgetter(*[
field.attname
if from_field == 'self' else
queryset.model._meta.get_field(from_field).attname
for from_field in field.from_fields
]) for field, related_objs in queryset._known_related_objects.items()
])) for field, related_objs in queryset._known_related_objects.items()
]
for row in compiler.results_iter(results):
obj = model_cls.from_db(db, init_list, row[model_fields_start:model_fields_end])
@ -80,11 +78,11 @@ class ModelIterable(BaseIterable):
setattr(obj, attr_name, row[col_pos])
# Add the known related objects to the model.
for field, rel_objs, rel_getters in known_related_objects:
for field, rel_objs, rel_getter in known_related_objects:
# Avoid overwriting objects loaded by, e.g., select_related().
if field.is_cached(obj):
continue
rel_obj_id = tuple([rel_getter(obj) for rel_getter in rel_getters])
rel_obj_id = rel_getter(obj)
try:
rel_obj = rel_objs[rel_obj_id]
except KeyError: