108 lines
2.7 KiB
Python
108 lines
2.7 KiB
Python
from django.db.models import FloatField, Func, IntegerField
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__all__ = [
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'CumeDist', 'DenseRank', 'FirstValue', 'Lag', 'LastValue', 'Lead',
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'NthValue', 'Ntile', 'PercentRank', 'Rank', '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.' %
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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('%s requires a non-null source expression.' % self.__class__.__name__)
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if nth is None or nth <= 0:
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raise ValueError('%s requires a positive integer as for nth.' % self.__class__.__name__)
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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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