#30564: Cannot create custom field that returns a queryset AND uses pre_save() -------------------------------------+------------------------------------- Reporter: Dan J | Owner: nobody Strohl | Type: Bug | Status: new Component: Database | Version: 2.2 layer (models, ORM) | Severity: Normal | Keywords: Triage Stage: | Has patch: 0 Unreviewed | Needs documentation: 0 | Needs tests: 0 Patch needs improvement: 0 | Easy pickings: 0 UI/UX: 0 | -------------------------------------+------------------------------------- I tried creating a custom field that would store a string that was a list of pks, then return that as a queryset. (yes, I could probably have done it using a many2many field, but I was (am) trying to reduce the number of db queries for this.
In any case, all seems to work OK until I implemented a def pre_save(self, model_instance, add) method on my custom field. What seems to be happening is that when the queryset comes back from the pre-save, it is run through the SQLInsertCompiler.prepare_value, which checks the value to see if it has a "resolve_expression" attrubute, which it assumes is then a SQL expression and then tries checking for "contains_column_references"... The QuerySet object DOES have the "resolve_expression" attribute, but does NOT have the others that are in the SQL expression objects. I suspect this doesn't come up much. My trace back Error Traceback (most recent call last): {{{ File "C:\Users\strohl\Documents\Project\Who\who_db\who_db_tests\test_model_methods.py", line 101, in setUp self.M1 = MixinTest.objects.create(name='M1') File "C:\Users\strohl\Documents\VirtualEnv\Who\lib\site- packages\django\db\models\manager.py", line 82, in manager_method return getattr(self.get_queryset(), name)(*args, **kwargs) File "C:\Users\strohl\Documents\VirtualEnv\Who\lib\site- packages\django\db\models\query.py", line 422, in create obj.save(force_insert=True, using=self.db) File "C:\Users\strohl\Documents\Project\Who\who_db\models.py", line 132, in save super(MixinTest, self).save(*args, **kwargs) File "C:\Users\strohl\Documents\VirtualEnv\Who\lib\site- packages\django\db\models\base.py", line 741, in save force_update=force_update, update_fields=update_fields) File "C:\Users\strohl\Documents\VirtualEnv\Who\lib\site- packages\django\db\models\base.py", line 779, in save_base force_update, using, update_fields, File "C:\Users\strohl\Documents\VirtualEnv\Who\lib\site- packages\django\db\models\base.py", line 870, in _save_table result = self._do_insert(cls._base_manager, using, fields, update_pk, raw) File "C:\Users\strohl\Documents\VirtualEnv\Who\lib\site- packages\django\db\models\base.py", line 908, in _do_insert using=using, raw=raw) File "C:\Users\strohl\Documents\VirtualEnv\Who\lib\site- packages\django\db\models\manager.py", line 82, in manager_method return getattr(self.get_queryset(), name)(*args, **kwargs) File "C:\Users\strohl\Documents\VirtualEnv\Who\lib\site- packages\django\db\models\query.py", line 1186, in _insert return query.get_compiler(using=using).execute_sql(return_id) File "C:\Users\strohl\Documents\VirtualEnv\Who\lib\site- packages\django\db\models\sql\compiler.py", line 1331, in execute_sql for sql, params in self.as_sql(): File "C:\Users\strohl\Documents\VirtualEnv\Who\lib\site- packages\django\db\models\sql\compiler.py", line 1275, in as_sql for obj in self.query.objs File "C:\Users\strohl\Documents\VirtualEnv\Who\lib\site- packages\django\db\models\sql\compiler.py", line 1275, in <listcomp> for obj in self.query.objs File "C:\Users\strohl\Documents\VirtualEnv\Who\lib\site- packages\django\db\models\sql\compiler.py", line 1274, in <listcomp> [self.prepare_value(field, self.pre_save_val(field, obj)) for field in fields] File "C:\Users\strohl\Documents\VirtualEnv\Who\lib\site- packages\django\db\models\sql\compiler.py", line 1205, in prepare_value if value.contains_column_references: AttributeError: 'Query' object has no attribute 'contains_column_references' }}} My custom field: {{{ #!python class PkListField(Field): empty_strings_allowed = False description = "PK List" default_error_messages = {} def __init__(self, *args, max_recs=100, max_pk_size=5, sep=',', ordered=None, as_pks=True, model=None, manager='objects', pre_save_func=None, **kwargs): self.pk_list_model_manager = manager self.max_recs = max_recs self.max_pk_size = max_pk_size self.sep = sep self.as_pks = as_pks self.ordered = ordered self.pre_save_func = pre_save_func self._pk_list_model = model if not as_pks and model is None: raise AttributeError('Model must be specified if not returning as_pks') if as_pks and ordered is not None and ordered != 'pk': raise AttributeError('Data can only be ordered by PKs when returning as pks') kwargs['max_length'] = ((max_pk_size + 2) * max_recs) + 1 kwargs['blank'] = True kwargs['default'] = sep + sep super().__init__(*args, **kwargs) @property def pk_list_model(self): if isinstance(self._pk_list_model, str): self._pk_list_model = apps.get_model(self._pk_list_model) return self._pk_list_model def deconstruct(self): name, path, args, kwargs = super().deconstruct() if self.pre_save_func is not None: kwargs['pre_save_func'] = self.pre_save_func if self.pk_list_model is not None: kwargs['model'] = self.pk_list_model if self.pk_list_model_manager is not 'objects': kwargs['manager'] = self.pk_list_model_manager if not self.as_pks: kwargs['as_pks'] = self.as_pks if self.max_recs != 100: kwargs['max_recs'] = self.max_recs if self.max_pk_size != 5: kwargs['max_pk_size'] = self.max_pk_size if self.sep != ',': kwargs['sep'] = self.sep if self.ordered is not None: kwargs['ordered'] = self.ordered del kwargs['max_length'] del kwargs['blank'] del kwargs['default'] return name, path, args, kwargs def get_internal_type(self): return "CharField" def conv_str_to_python(self, value): def conv_obj(obj_in): if obj_in is None: return [] elif isinstance(obj_in, int): return [obj_in] elif isinstance(obj_in, str): if self.sep in obj_in: return conv_obj(obj_in.strip().strip(self.sep).split(self.sep)) if obj_in: return [int(obj_in.strip())] else: return [] elif issubclass(obj_in.__class__, models.Model): return [obj_in.pk] else: try: tmp_ret = [] for item in obj_in: tmp_ret.extend(conv_obj(item)) return tmp_ret except TypeError: raise ValidationError('Invalid object type: %r' % obj_in) if issubclass(value.__class__, models.QuerySet): if self.as_pks: return list(value.values_list('pk', flat=True)) else: return value if not value: value = [] else: value = conv_obj(value) if self.as_pks: if self.ordered == 'pk': value.sort() return value tmp_mgr = getattr(self.pk_list_model, self.pk_list_model_manager) print('in conv_to_python: value= %r' % value) # if value: tmp_ret = tmp_mgr.filter(pk__in=value) if self.ordered: tmp_ret = tmp_ret.order_by(*make_list(self.ordered)) print('in conv_to_python: returning filtered = %r' % tmp_ret) return tmp_ret # else: # tmp_ret = tmp_mgr.none() # print('in conv_to_python: returning none = %r' % tmp_ret) # return tmp_ret def to_python(self, value): print(f'IN ({self.attname}) to_python({repr(value)})') tmp_ret = self.conv_str_to_python(value) print(f'OUT ({self.attname}) to_python({repr(tmp_ret)})') return tmp_ret def from_db_value(self, value, expression, connection): print(f'IN ({self.attname}) from_db_value({repr(value)})') tmp_ret = self.conv_str_to_python(value) print(f'OUT ({self.attname}) from_db_value({repr(tmp_ret)})') return tmp_ret def conv_to_str(self, value, wrapped=True): def conv_obj(obj_in): if obj_in is None: return [] elif isinstance(obj_in, int): return [str(obj_in)] elif isinstance(obj_in, str): if self.sep in obj_in: return conv_obj(obj_in.strip().strip(self.sep).split(self.sep)) if obj_in: return [obj_in.strip()] else: return [] elif issubclass(obj_in.__class__, models.Model): return [str(obj_in.pk)] else: try: tmp_ret = [] for item in obj_in: tmp_ret.extend(conv_obj(item)) return tmp_ret except TypeError: raise ValidationError('Invalid object type: %r' % obj_in) if issubclass(value.__class__, models.QuerySet): value = list(value.values_list('pk', flat=True)) value = self.sep.join(conv_obj(value)) if wrapped: return self.sep + value + self.sep else: return value def get_db_prep_value(self, value, connection, prepared=False): print(f'IN ({self.attname}) get_db_prep_value({repr(value)})') if not prepared: value = self.get_prep_value(value) value = super(PkListField, self).get_db_prep_value(value, connection, prepared=True) print(f'OUT ({self.attname}) get_db_prep_value({repr(value)})') return value def get_prep_value(self, value): print(f'IN ({self.attname}) get_prep_value({repr(value)})') value = super().get_prep_value(value) value = self.conv_to_str(value) print(f'OUT ({self.attname}) get_prep_value({repr(value)})') return value def pre_save(self, model_instance, add): if self.pre_save_func is not None: value = super(PkListField, self).pre_save(model_instance, add) value = self.pre_save_func(value=value, field=self.attname, model=model_instance, add=add) setattr(model_instance, self.attname, value) print(f'({self.attname}) OUT pre_Save({repr(value)})') return value else: value = super().pre_save(model_instance, add) print(f'OUT ({self.attname}) pre_save({repr(value)})') return value }}} -- Ticket URL: <https://code.djangoproject.com/ticket/30564> Django <https://code.djangoproject.com/> The 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