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