48 lines
1.8 KiB
Python
48 lines
1.8 KiB
Python
from django.db.models.expressions import F, OrderBy
|
|
|
|
|
|
class OrderableAggMixin:
|
|
|
|
def __init__(self, expression, ordering=(), **extra):
|
|
if not isinstance(ordering, (list, tuple)):
|
|
ordering = [ordering]
|
|
ordering = ordering or []
|
|
# Transform minus sign prefixed strings into an OrderBy() expression.
|
|
ordering = (
|
|
(OrderBy(F(o[1:]), descending=True) if isinstance(o, str) and o[0] == '-' else o)
|
|
for o in ordering
|
|
)
|
|
super().__init__(expression, **extra)
|
|
self.ordering = self._parse_expressions(*ordering)
|
|
|
|
def resolve_expression(self, *args, **kwargs):
|
|
self.ordering = [expr.resolve_expression(*args, **kwargs) for expr in self.ordering]
|
|
return super().resolve_expression(*args, **kwargs)
|
|
|
|
def as_sql(self, compiler, connection):
|
|
if self.ordering:
|
|
self.extra['ordering'] = 'ORDER BY ' + ', '.join((
|
|
ordering_element.as_sql(compiler, connection)[0]
|
|
for ordering_element in self.ordering
|
|
))
|
|
else:
|
|
self.extra['ordering'] = ''
|
|
return super().as_sql(compiler, connection)
|
|
|
|
def get_source_expressions(self):
|
|
return self.source_expressions + self.ordering
|
|
|
|
def get_source_fields(self):
|
|
# Filter out fields contributed by the ordering expressions as
|
|
# these should not be used to determine which the return type of the
|
|
# expression.
|
|
return [
|
|
e._output_field_or_none
|
|
for e in self.get_source_expressions()[:self._get_ordering_expressions_index()]
|
|
]
|
|
|
|
def _get_ordering_expressions_index(self):
|
|
"""Return the index at which the ordering expressions start."""
|
|
source_expressions = self.get_source_expressions()
|
|
return len(source_expressions) - len(self.ordering)
|