def CountIf(field, expression, **extra):
return Count(
Case(
When(expression, then=F(field), **extra),
default=None,
output_field=Field(),
))
def resolve_ref(name: str, *_: Any, **__: Any) -> 'Col':
from django.db.models.expressions import Col
from django.db.models.fields import Field
# We need to do some faking of the ref resolution.
# This essentially enables us to have a bit more complete
# workings of F().
# An interesting point to raise here is, we need to pass a Field in.
# However, it doesn't need to be the "correct" field. At this point,
# all conversion has been done, so now we just need to get a valid
# target in.
return Col(name, Field())
def field(self):
return Field(name=sentinel.FIELD_NAME)
def __init__(self, token):
"""
Constructor for `QueryField`. This constructor tries to define a valid query field with
all corresponding values for further processing in the context of DB querying.
Example:
QueryField('comment') -> Machine.comment
QueryField('comment_length') -> Machine.comment (for querying the char length)
QueryField('ipv4') -> Machine.ipv4 (dynamic field)
QueryField('installations__comment') -> Machine.installations.comment (related field)
"""
self._field = None
self._related_name = None
self._verbose_name = None
self._dynamic = False
self._pre_function = None
self._post_function = None
if self.LENGTH_SUFFIX in token:
token = token.replace(self.LENGTH_SUFFIX, '')
self._annotation = self.LENGTH_SUFFIX
else:
self._annotation = None
try:
self._field = self.MAPPING[token]['field']
self._verbose_name = self.MAPPING[token].get('verbose_name')
if not self._verbose_name:
self._verbose_name = Machine._meta.get_field(
self._field.name).verbose_name
self._related_name = self.MAPPING[token].get('related_name')
self._pre_function = self.MAPPING[token].get('pre')
self._post_function = self.MAPPING[token].get('post')
except KeyError:
pass
if not self._field and (token in self.DYNAMIC_FIELDS):
self._field = Field(name=token)
self._verbose_name = self.DYNAMIC_FIELDS[
self._field.name]['verbose_name']
self._dynamic_field_function = self.DYNAMIC_FIELDS[
self._field.name]['function']
self._dynamic = True
if not self._field:
try:
self._field = Machine._meta.get_field(token)
self._verbose_name = self._field.verbose_name
except FieldDoesNotExist:
pass
if not self._field:
related_name = '__'.join(token.split('__')[:-1])
field_name = token.split('__')[-1]
if related_name:
for token, values in self.MAPPING.items():
if related_name == values.get('related_name'):
if field_name == values['field'].name:
self._field = self.MAPPING[token]['field']
self._related_name = related_name
self._verbose_name = self.MAPPING[token][
'verbose_name']
self._pre_function = self.MAPPING[token].get('pre')
self._post_function = self.MAPPING[token].get(
'post')
if not self._field:
raise ValueError("Unknown field '{}'!".format(token))
def transform_to_field(key):
field = Field(name=key)
return field
