Django 1.9.5：偶尔出现反向查找字段的 FieldError
Django 1.9.5: FieldError for reverse lookup fields occasionally
我在尝试 运行 预取 Queryset 的 objects.all() 时，在 Django 中遇到令人沮丧的间歇性错误。有一个问题，在查询集实例化和 运行 迭代之间，偶尔 model._meta 似乎缺少字段。就好像查询集的预取实际上没有及时 运行 对象列表的迭代。
在此示例中，data.service_log 只是一个查询集，其中包含一些名为 servicelog 的预取项。当我运行 shell 中的查询集时，我可以查看查询集上self.names_to_path(lookup_splitted, self.get_meta()) 方法中的所有字段。它们都在那里，特别是 "servicelog."
请注意此错误的回溯，它说 "servicelog" 不是可用字段，但它在可供选择的字段列表中列出。这似乎是一个 Django 错误，但我不能确定，因为我无法解释或隔离该行为。我不可能是唯一遇到此错误的人。好像是在django/db/models/sql/query.py中的names_to_paths()方法。这是无法解析的代码：
query.py names_to_paths():
field = None
try:
field = opts.get_field(name)
except FieldDoesNotExist:
if name in self.annotation_select:
field = self.annotation_select[name].output_field
if field is not None:
# Fields that contain one-to-many relations with a generic
# model (like a GenericForeignKey) cannot generate reverse
# relations and therefore cannot be used for reverse querying.
if field.is_relation and not field.related_model:
raise FieldError(
"Field %r does not generate an automatic reverse "
"relation and therefore cannot be used for reverse "
"querying. If it is a GenericForeignKey, consider "
"adding a GenericRelation." % name
)
try:
model = field.model._meta.concrete_model
except AttributeError:
model = None
else:
# We didn't find the current field, so move position back
# one step.
pos -= 1
if pos == -1 or fail_on_missing:
field_names = list(get_field_names_from_opts(opts))
available = sorted(field_names + list(self.annotation_select))
raise FieldError("Cannot resolve keyword %r into field. "
"Choices are: %s" % (name, ", .join(available)))
break
field does not get set in the first try, then the condition statement如果字段不是 Nonefails so we enter theelseblock. There theposgets reduced by one, but since this field is 'servicelog' it is already at 0. However, when I try this in the shell, it always finds thefieldwithopts.get_field('servicelog')`。只有当来自 WSGI 和 Apache2 的 运行 时才会出现此故障。同样，并非所有时间都如此，这使得测试极其困难。我对此感到困惑，并且不确定在哪里寻找线索。如果有人对要探索的内容有任何想法，我将不胜感激。
Traceback (most recent call last):
File "/var/www/fast/services/views/edit.py", line 12897, in service_log
for service in data.service_log:
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 258, in __iter__
self._fetch_all()
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 1076, in _fetch_all
self._prefetch_related_objects()
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 656, in _prefetch_related_objects
prefetch_related_objects(self._result_cache, self._prefetch_related_lookups)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 1457, in prefetch_related_objects
obj_list, additional_lookups = prefetch_one_level(obj_list, prefetcher, lookup, level)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 1556, in prefetch_one_level
prefetcher.get_prefetch_queryset(instances, lookup.get_current_queryset(level)))
File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/related_descriptors.py", line 802, in get_prefetch_queryset
queryset = queryset._next_is_sticky().filter(**query)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 790, in filter
return self._filter_or_exclude(False, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 808, in _filter_or_exclude
clone.query.add_q(Q(*args, **kwargs))
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 1243, in add_q
clause, _ = self._add_q(q_object, self.used_aliases)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 1269, in _add_q
allow_joins=allow_joins, split_subq=split_subq,
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 1149, in build_filter
lookups, parts, reffed_expression = self.solve_lookup_type(arg)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 1035, in solve_lookup_type
_, field, _, lookup_parts = self.names_to_path(lookup_splitted, self.get_meta())
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 1330, in names_to_path
"Choices are: %s" % (name, ", ".join(available)))
FieldError: Cannot resolve keyword u'servicelog' into field. Choices are: additional_county_worker_notes, adoption_disrupted, adoption_first_name, adoption_last_name, adoption_middle_name, adoption_placement_date, adoption_placement_reason, adoption_placement_reason_id, adoption_placement_type, adoption_risk_level, adoption_risk_level_id, adoption_termination_date, adoption_termination_destination, adoption_termination_reason, adoption_termination_reason_id, adoptive_placement, agency, agency_id, all_items_outstanding, all_items_past_due, appeal_process_date, attached_file, attends_college, attorney_email_address, attorney_email_address_id, attorney_fax, attorney_fax_id, attorney_investigator_email_address, attorney_investigator_email_address_id, attorney_investigator_fax, attorney_investigator_fax_id, attorney_investigator_name, attorney_investigator_phone, attorney_investigator_phone_id, attorney_name, attorney_phone, attorney_phone_id, blood_related_to_applicants, blood_relationship, casa_email_address, casa_email_address_id, casa_fax, casa_fax_id, casa_name, casa_phone, casa_phone_id, certification_items_outstanding, certification_items_past_due, classification, classification_id, client, client_id, county_adoption_worker, county_adoption_worker_cell, county_adoption_worker_cell_id, county_adoption_worker_email_address, county_adoption_worker_email_address_id, county_adoption_worker_fax, county_adoption_worker_fax_id, county_adoption_worker_office, county_adoption_worker_office_id, county_adoption_worker_phone, county_adoption_worker_phone_id, county_adoption_worker_title, county_case_number, county_worker, county_worker_cell, county_worker_cell_id, county_worker_email_address, county_worker_email_address_id, county_worker_fax, county_worker_fax_id, county_worker_office, county_worker_office_id, county_worker_phone, county_worker_phone_id, county_worker_title, court, court_case_name, court_case_number, court_department, court_id, created, current_grade, date_identified_adoptive, date_placed_with_home, deleted, discharge_summary, eligibility_worker, eligibility_worker_email_address, eligibility_worker_email_address_id, eligibility_worker_phone, eligibility_worker_phone_id, emergency_placement, employed_80_hours, enable_discharge_summary, expected_type, expected_type_id, extended_family_contact_allowed, final_payment_amount, finalization_date, foreign_placement, hearing_36626_date, homestudy, id, incident_placement_1, incident_placement_2, incident_placement_3, incident_placement_4, individualized_plan_review, inhousemove, interpretive_summary, item_due, items_approved, items_pending, items_rejected, items_update_requested, la_county_id, medi_cal, medi_cal_eligibility_phone, medi_cal_eligibility_phone_id, medi_cal_eligibility_worker, medi_cal_id, modified, monthly_monitored_visit_hours, mother_child, move_in_type, move_out_type, new_protective_custody_petition, non_minor_dependent, non_truant, notes, number_of_files_required, other_school_contact, other_school_contact_first_name, other_school_contact_last_name, parent_payment_override_annually, parent_payment_override_daily, parent_payment_override_monthly, parental_contact_allowed, parental_group, parental_group_id, payment_amount, percent_certified, percent_items_complete, person_number, placement, placement_date, placement_id, placement_payment_override_annually, placement_payment_override_daily, placement_payment_override_monthly, placement_reason, placement_reason_details, placement_reason_id, placement_self, placer_shelter_bed, prior_placement, progress_summary, projected_adoption_36626_date, projected_adoption_finalization_date, projected_adoption_placement_date, recordreview, requires_educational_support, requires_mental_health_services, respite, school, school_different, school_id, school_liaison_email, school_liaison_first_name, school_liaison_last_name, school_liaison_phone, school_liaison_phone_extension, school_notes, serial_number, servicecontact_onbehalf, servicedeliverylog, servicelog, social_worker_at_termination, social_worker_at_termination_id, special_health_care_needs, state_case_number, teachers, termination_date, termination_destination, termination_reason, termination_reason_details, termination_reason_id, therapist, therapy_code, therapy_supervision_requirements, treatment_abilities, treatment_needs, treatment_preferences, treatment_strengths, treatmentneed, update_requested, update_requested_by, update_requested_by_id, update_requested_date, update_requested_note, updateable, use_number_required, uses_psychotropic_medication, visit_frequency_override, visit_frequency_override_id, visitation_restrictions, who_can_pickup_at_home, who_can_pickup_at_school, who_can_visit
更新 - 添加 models/offending 查看代码
models.py
class ParentalGroup(models.Model):
many fields...
class Placement(models.Model):
parental_group = models.ForeignKey(ParentalGroup, null=True, blank=True)
many more fields...
class ServiceLog(models.Model):
parental_group = models.ForeignKey(ParentalGroup, null=True, blank=True)
placement = models.ManyToManyField(Placement, blank=True)
many more fields...
views.py:
data.service_log = ServiceLog.objects.filter(
parental_group=data.pg,
).prefetch_related(
Prefetch(
'placement',
queryset=Placement.objects.all(),
to_attr='placements'
),
)
for service in data.service_log:
some code to generate data to pass to template...
return render_to_response(...)
我在 Gunicorn/Django runserver 上使用 Django 1.8.6 时遇到了类似的问题。我也没有设法在 shell/notebook 环境中重现错误。
我通过在 ManyToManyField 中添加 related_name to the ManyToManyField. I used a through model 解决了随机出现的 FieldError。
你的情况：
class ServiceLog(models.Model):
parental_group = models.ForeignKey(ParentalGroup, null=True, blank=True)
placement = models.ManyToManyField(Placement, blank=True, related_name='servicelog')
一月
我在尝试 运行 预取 Queryset 的 objects.all() 时，在 Django 中遇到令人沮丧的间歇性错误。有一个问题，在查询集实例化和 运行 迭代之间，偶尔 model._meta 似乎缺少字段。就好像查询集的预取实际上没有及时 运行 对象列表的迭代。
在此示例中，data.service_log 只是一个查询集，其中包含一些名为 servicelog 的预取项。当我运行 shell 中的查询集时，我可以查看查询集上self.names_to_path(lookup_splitted, self.get_meta()) 方法中的所有字段。它们都在那里，特别是 "servicelog."
请注意此错误的回溯，它说 "servicelog" 不是可用字段，但它在可供选择的字段列表中列出。这似乎是一个 Django 错误，但我不能确定，因为我无法解释或隔离该行为。我不可能是唯一遇到此错误的人。好像是在django/db/models/sql/query.py中的names_to_paths()方法。这是无法解析的代码：
query.py names_to_paths():
field = None
try:
field = opts.get_field(name)
except FieldDoesNotExist:
if name in self.annotation_select:
field = self.annotation_select[name].output_field
if field is not None:
# Fields that contain one-to-many relations with a generic
# model (like a GenericForeignKey) cannot generate reverse
# relations and therefore cannot be used for reverse querying.
if field.is_relation and not field.related_model:
raise FieldError(
"Field %r does not generate an automatic reverse "
"relation and therefore cannot be used for reverse "
"querying. If it is a GenericForeignKey, consider "
"adding a GenericRelation." % name
)
try:
model = field.model._meta.concrete_model
except AttributeError:
model = None
else:
# We didn't find the current field, so move position back
# one step.
pos -= 1
if pos == -1 or fail_on_missing:
field_names = list(get_field_names_from_opts(opts))
available = sorted(field_names + list(self.annotation_select))
raise FieldError("Cannot resolve keyword %r into field. "
"Choices are: %s" % (name, ", .join(available)))
break
field does not get set in the first try, then the condition statement如果字段不是 Nonefails so we enter theelseblock. There theposgets reduced by one, but since this field is 'servicelog' it is already at 0. However, when I try this in the shell, it always finds thefieldwithopts.get_field('servicelog')`。只有当来自 WSGI 和 Apache2 的 运行 时才会出现此故障。同样，并非所有时间都如此，这使得测试极其困难。我对此感到困惑，并且不确定在哪里寻找线索。如果有人对要探索的内容有任何想法，我将不胜感激。
Traceback (most recent call last):
File "/var/www/fast/services/views/edit.py", line 12897, in service_log
for service in data.service_log:
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 258, in __iter__
self._fetch_all()
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 1076, in _fetch_all
self._prefetch_related_objects()
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 656, in _prefetch_related_objects
prefetch_related_objects(self._result_cache, self._prefetch_related_lookups)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 1457, in prefetch_related_objects
obj_list, additional_lookups = prefetch_one_level(obj_list, prefetcher, lookup, level)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 1556, in prefetch_one_level
prefetcher.get_prefetch_queryset(instances, lookup.get_current_queryset(level)))
File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/related_descriptors.py", line 802, in get_prefetch_queryset
queryset = queryset._next_is_sticky().filter(**query)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 790, in filter
return self._filter_or_exclude(False, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 808, in _filter_or_exclude
clone.query.add_q(Q(*args, **kwargs))
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 1243, in add_q
clause, _ = self._add_q(q_object, self.used_aliases)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 1269, in _add_q
allow_joins=allow_joins, split_subq=split_subq,
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 1149, in build_filter
lookups, parts, reffed_expression = self.solve_lookup_type(arg)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 1035, in solve_lookup_type
_, field, _, lookup_parts = self.names_to_path(lookup_splitted, self.get_meta())
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 1330, in names_to_path
"Choices are: %s" % (name, ", ".join(available)))
FieldError: Cannot resolve keyword u'servicelog' into field. Choices are: additional_county_worker_notes, adoption_disrupted, adoption_first_name, adoption_last_name, adoption_middle_name, adoption_placement_date, adoption_placement_reason, adoption_placement_reason_id, adoption_placement_type, adoption_risk_level, adoption_risk_level_id, adoption_termination_date, adoption_termination_destination, adoption_termination_reason, adoption_termination_reason_id, adoptive_placement, agency, agency_id, all_items_outstanding, all_items_past_due, appeal_process_date, attached_file, attends_college, attorney_email_address, attorney_email_address_id, attorney_fax, attorney_fax_id, attorney_investigator_email_address, attorney_investigator_email_address_id, attorney_investigator_fax, attorney_investigator_fax_id, attorney_investigator_name, attorney_investigator_phone, attorney_investigator_phone_id, attorney_name, attorney_phone, attorney_phone_id, blood_related_to_applicants, blood_relationship, casa_email_address, casa_email_address_id, casa_fax, casa_fax_id, casa_name, casa_phone, casa_phone_id, certification_items_outstanding, certification_items_past_due, classification, classification_id, client, client_id, county_adoption_worker, county_adoption_worker_cell, county_adoption_worker_cell_id, county_adoption_worker_email_address, county_adoption_worker_email_address_id, county_adoption_worker_fax, county_adoption_worker_fax_id, county_adoption_worker_office, county_adoption_worker_office_id, county_adoption_worker_phone, county_adoption_worker_phone_id, county_adoption_worker_title, county_case_number, county_worker, county_worker_cell, county_worker_cell_id, county_worker_email_address, county_worker_email_address_id, county_worker_fax, county_worker_fax_id, county_worker_office, county_worker_office_id, county_worker_phone, county_worker_phone_id, county_worker_title, court, court_case_name, court_case_number, court_department, court_id, created, current_grade, date_identified_adoptive, date_placed_with_home, deleted, discharge_summary, eligibility_worker, eligibility_worker_email_address, eligibility_worker_email_address_id, eligibility_worker_phone, eligibility_worker_phone_id, emergency_placement, employed_80_hours, enable_discharge_summary, expected_type, expected_type_id, extended_family_contact_allowed, final_payment_amount, finalization_date, foreign_placement, hearing_36626_date, homestudy, id, incident_placement_1, incident_placement_2, incident_placement_3, incident_placement_4, individualized_plan_review, inhousemove, interpretive_summary, item_due, items_approved, items_pending, items_rejected, items_update_requested, la_county_id, medi_cal, medi_cal_eligibility_phone, medi_cal_eligibility_phone_id, medi_cal_eligibility_worker, medi_cal_id, modified, monthly_monitored_visit_hours, mother_child, move_in_type, move_out_type, new_protective_custody_petition, non_minor_dependent, non_truant, notes, number_of_files_required, other_school_contact, other_school_contact_first_name, other_school_contact_last_name, parent_payment_override_annually, parent_payment_override_daily, parent_payment_override_monthly, parental_contact_allowed, parental_group, parental_group_id, payment_amount, percent_certified, percent_items_complete, person_number, placement, placement_date, placement_id, placement_payment_override_annually, placement_payment_override_daily, placement_payment_override_monthly, placement_reason, placement_reason_details, placement_reason_id, placement_self, placer_shelter_bed, prior_placement, progress_summary, projected_adoption_36626_date, projected_adoption_finalization_date, projected_adoption_placement_date, recordreview, requires_educational_support, requires_mental_health_services, respite, school, school_different, school_id, school_liaison_email, school_liaison_first_name, school_liaison_last_name, school_liaison_phone, school_liaison_phone_extension, school_notes, serial_number, servicecontact_onbehalf, servicedeliverylog, servicelog, social_worker_at_termination, social_worker_at_termination_id, special_health_care_needs, state_case_number, teachers, termination_date, termination_destination, termination_reason, termination_reason_details, termination_reason_id, therapist, therapy_code, therapy_supervision_requirements, treatment_abilities, treatment_needs, treatment_preferences, treatment_strengths, treatmentneed, update_requested, update_requested_by, update_requested_by_id, update_requested_date, update_requested_note, updateable, use_number_required, uses_psychotropic_medication, visit_frequency_override, visit_frequency_override_id, visitation_restrictions, who_can_pickup_at_home, who_can_pickup_at_school, who_can_visit
更新 - 添加 models/offending 查看代码
models.py
class ParentalGroup(models.Model):
many fields...
class Placement(models.Model):
parental_group = models.ForeignKey(ParentalGroup, null=True, blank=True)
many more fields...
class ServiceLog(models.Model):
parental_group = models.ForeignKey(ParentalGroup, null=True, blank=True)
placement = models.ManyToManyField(Placement, blank=True)
many more fields...
views.py:
data.service_log = ServiceLog.objects.filter(
parental_group=data.pg,
).prefetch_related(
Prefetch(
'placement',
queryset=Placement.objects.all(),
to_attr='placements'
),
)
for service in data.service_log:
some code to generate data to pass to template...
return render_to_response(...)
我在 Gunicorn/Django runserver 上使用 Django 1.8.6 时遇到了类似的问题。我也没有设法在 shell/notebook 环境中重现错误。
我通过在 ManyToManyField 中添加 related_name to the ManyToManyField. I used a through model 解决了随机出现的 FieldError。
你的情况：
class ServiceLog(models.Model):
parental_group = models.ForeignKey(ParentalGroup, null=True, blank=True)
placement = models.ManyToManyField(Placement, blank=True, related_name='servicelog')
一月