Easy value caching on Django.
Project description
django-cached-fields
Cached fields for Django
Usage
Defining a basic Cached Field
The first argument of the CachedField constructor can be the name of a method on the class.
This method only works with field triggers as signal triggers will require a CachedFieldSignalHandler
.
class Invoice(models.Model):
name = models.TextField(null=False)
quantity = models.IntegerField()
amount = models.IntegerField(null=False)
def calc_total(self):
self.total = self.quantity * self.amount
total = CachedIntegerField(
'calc_total',
field_triggers=[
'amount',
],
timeout=timedelta(seconds=5),
)
If you would like your cached field's callback to be triggered by a signal, you will need to create a signal handler.
class InvoiceSignalHandler(CachedFieldSignalHandler):
def calc_total(instance):
instance.total = instance.quantity * instance.amount
@for_class('Customer')
def cutomer_total(customer):
return invoice.quantity * invoice.amount
@for_class('Supplier')
def supplier_total(supplier):
invoice = supplier.invoice.last()
return invoice.quantity * invoice.amount
If you would like to offload task processing to Celery, django-cached-fields can handle that for you automatically.
settings.py
CACHED_FIELDS_CELERY_ENABLED = True
CACHED_FIELDS_CELERY = {
"queue": "default"
}
If you'd like to offload a recalculation to a specific queue, you can do this.
class InvoiceSignalHandler(CachedFieldSignalHandler):
def calc_total(instance):
instance.total = instance.quantity * instance.amount
@for_class('Customer', queue="low_priority")
def cutomer_total(customer):
invoices = customer.invoices.all()
for i in invoices:
i.cache_toolkit.update_cache('total', i.quantity * i.amount)
i.save()
@for_class('Supplier')
def supplier_total(supplier):
invoice = supplier.invoice.last()
invoice.total = invoice.quantity * invoice.amount
Force Recalculation
ym = YourModel.objects.create(name="fart", amount=6)
ym.cache_toolchain.refresh_field('total')
Get last time the cache was updated
For when you need to run queries ```python In [2]: print(ym.total_last_update) Out[2]: datetime.datetime(2019,10,30,4,30,54)
In [3]: YourModel.objcts.filter(total_last_update__date__gte=date(2019,10,1)).exists() Out[3]: True
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