autoupdated database fields for model methods
Project description
django-computedfields
django-computedfields provides autoupdated database fields for model methods.
Tested with Django 2.2 and 3.0 (Python 3.6 to 3.8).
Example
Just derive your model from ComputedFieldsModel
and place
the @computed
decorator at a method:
from django.db import models
from computedfields.models import ComputedFieldsModel, computed
class MyModel(ComputedFieldsModel):
name = models.CharField(max_length=32)
@computed(models.CharField(max_length=32), depends=[['self', ['name']]])
def computed_field(self):
return self.name.upper()
computed_field
will be turned into a real database field
and can be accessed and searched like any other database field.
During saving the associated method gets called and it’s result
written to the database. With the method compute('fieldname')
you can inspect the value that will be written, which is useful
if you have pending changes:
>>> person = MyModel(forename='berty')
>>> person.computed_field # empty since not saved yet
>>> person.compute('computed_field') # outputs 'BERTY'
>>> person.save()
>>> person.computed_field # outputs 'BERTY'
The depends
keyword argument can be used with any relation to indicate dependencies to fields on other models as well:
from django.db import models
from computedfields.models import ComputedFieldsModel, computed
class MyModel(ComputedFieldsModel):
name = models.CharField(max_length=32)
fk = models.ForeignKey(SomeModel)
@computed(models.CharField(max_length=32), depends=[['self', ['name']], ['fk', ['fieldname']]])
def computed_field(self):
return self.name.upper() + self.fk.fieldname
Now changes to self.name
or fk.fieldname
will update computed_field
.
Documentation
The documentation can be found here.
Changelog
- 0.1.2
- bugfix: o2o reverse name access
- add docs about model inheritance support
- 0.1.1
- bugfix: add missing migration
- 0.1.0
- fix recursion on empty queryset
- dependency expansion on M2M fields
m2m_changed
handler with filtering on m2m fields- remove custom metaclass, introducing Resolver class
- new decorator
@precomputed
for custom save methods - old depends syntax removed
- docs update
- 0.0.23:
- Bugfix: Fixing leaking computed fields in model inheritance.
- 0.0.22:
- Automatic dependency expansion on reverse relations.
- Example documentation.
- 0.0.21:
- Bugfix: Fixing undefined _batchsize for pickled map usage.
- 0.0.20
- Use
bulk_update
for computed field updates. - Allow custom update optimizations with select_related and prefetch_related.
- Respect computed field MRO in
compute
. - Allow updates on local computed fields from
update_dependent
simplifying bulk actions onComputedFieldsModel
.
- Use
- 0.0.19
- Better graph expansion on relation paths with support for update_fields.
- 0.0.18
- New depends syntax deprecating the old one.
- MRO of local computed field methods implemented.
- 0.0.17
- Dropped Python 2.7 and Django 1.11 support.
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