File size: 2,841 Bytes
02bfabd | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 | 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",
]
class CumeDist(Func):
function = "CUME_DIST"
output_field = FloatField()
window_compatible = True
class DenseRank(Func):
function = "DENSE_RANK"
output_field = IntegerField()
window_compatible = True
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
class Lag(LagLeadFunction):
function = "LAG"
class LastValue(Func):
arity = 1
function = "LAST_VALUE"
window_compatible = True
class Lead(LagLeadFunction):
function = "LEAD"
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
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)
class PercentRank(Func):
function = "PERCENT_RANK"
output_field = FloatField()
window_compatible = True
class Rank(Func):
function = "RANK"
output_field = IntegerField()
window_compatible = True
class RowNumber(Func):
function = "ROW_NUMBER"
output_field = IntegerField()
window_compatible = True
|