Source code for django.db.models.functions.window
from django.db.models.expressions import Func
from django.db.models.fields import FloatField, IntegerField
__all__ = [
'CumeDist', 'DenseRank', 'FirstValue', 'Lag', 'LastValue', 'Lead',
'NthValue', 'Ntile', 'PercentRank', 'Rank', 'RowNumber',
]
[docs]class CumeDist(Func):
function = 'CUME_DIST'
output_field = FloatField()
window_compatible = True
[docs]class DenseRank(Func):
function = 'DENSE_RANK'
output_field = IntegerField()
window_compatible = True
[docs]class FirstValue(Func):
arity = 1
function = 'FIRST_VALUE'
window_compatible = True
class LagLeadFunction(Func):
window_compatible = True
def __init__(self, expression, offset=1, default=None, **extra):
if expression is None:
raise ValueError(
'%s requires a non-null source expression.' %
self.__class__.__name__
)
if offset is None or offset <= 0:
raise ValueError(
'%s requires a positive integer for the offset.' %
self.__class__.__name__
)
args = (expression, offset)
if default is not None:
args += (default,)
super().__init__(*args, **extra)
def _resolve_output_field(self):
sources = self.get_source_expressions()
return sources[0].output_field
[docs]class Lag(LagLeadFunction):
function = 'LAG'
[docs]class LastValue(Func):
arity = 1
function = 'LAST_VALUE'
window_compatible = True
[docs]class Lead(LagLeadFunction):
function = 'LEAD'
[docs]class NthValue(Func):
function = 'NTH_VALUE'
window_compatible = True
def __init__(self, expression, nth=1, **extra):
if expression is None:
raise ValueError('%s requires a non-null source expression.' % self.__class__.__name__)
if nth is None or nth <= 0:
raise ValueError('%s requires a positive integer as for nth.' % self.__class__.__name__)
super().__init__(expression, nth, **extra)
def _resolve_output_field(self):
sources = self.get_source_expressions()
return sources[0].output_field
[docs]class Ntile(Func):
function = 'NTILE'
output_field = IntegerField()
window_compatible = True
def __init__(self, num_buckets=1, **extra):
if num_buckets <= 0:
raise ValueError('num_buckets must be greater than 0.')
super().__init__(num_buckets, **extra)
[docs]class PercentRank(Func):
function = 'PERCENT_RANK'
output_field = FloatField()
window_compatible = True
[docs]class Rank(Func):
function = 'RANK'
output_field = IntegerField()
window_compatible = True
[docs]class RowNumber(Func):
function = 'ROW_NUMBER'
output_field = IntegerField()
window_compatible = True