pip install django-cte
Simple CTE queries can be constructed using With. A custom CTEManager is
used to add the CTE to the final query.
from django_cte import CTEManager, With
class Order(Model):
objects = CTEManager()
id = AutoField(primary_key=True)
region = ForeignKey("Region", on_delete=CASCADE)
amount = IntegerField(default=0)
cte = With(
Order.objects
.values("region_id")
.annotate(total=Sum("amount"))
)
orders = (
cte.join(Order, region=cte.col.region_id)
.with_cte(cte)
.annotate(region_total=cte.col.total)
.order_by("amount")
)Orders returned by this query will have a region_total attribute containing
the sum of all order amounts in the order's region.
If you need to use a custom QuerySets these should have a base class derived
from QTEQuerySet.
class PremiumOrdersQueySet(CTEQuerySet): return self.filter(amount__gt=100)
class PremiumOrders(Orders): class Meta: proxy = True
objects = PremiumOrdersQueySet.as_manager()
These can also be use with custom Manager or Manager and QuerySet
class CustomManager(CTEManager): def special_method(self): return
class AltOrders(Orders): class Meta: proxy = True
premium = CustomManager.from_queryset(PremiumOrdersQueySet)()
objects = CustomManager()
Recursive CTE queries can be constructed using With.recursive.
class Region(Model):
objects = CTEManager()
name = TextField(primary_key=True)
parent = ForeignKey("self", null=True, on_delete=CASCADE)
def make_regions_cte(cte):
return Region.objects.filter(
# start with root nodes
parent__isnull=True
).values(
"name",
path=F("name"),
depth=Value(0, output_field=IntegerField()),
).union(
# recursive union: get descendants
cte.join(Region, parent=cte.col.name).values(
"name",
path=Concat(
cte.col.path, Value("\x01"), F("name"),
output_field=TextField(),
),
depth=cte.col.depth + Value(1, output_field=IntegerField()),
),
all=True,
)
cte = With.recursive(make_regions_cte)
regions = (
cte.join(Region, name=cte.col.name)
.with_cte(cte)
.annotate(
path=cte.col.path,
depth=cte.col.depth,
)
.order_by("path")
)Regions returned by this query will have path and depth attributes. The
results will be ordered by path (hierarchically by region name). In this case
path is a '\x01'-delimited string of region names starting with the root
region.
See tests for more advanced examples.
cd django-cte
mkvirtualenv cte # or however you choose to setup your environment
pip install django nose flake8
nosetests
flake8 --config=setup.cfg
Package and upload the generated files.
pip install -r pkg-requires.txt
python setup.py sdist bdist_wheel
twine upload dist/*