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- """
- Classes to represent the definitions of aggregate functions.
- """
- from django.core.exceptions import FieldError
- from django.db.models.expressions import Case, Func, Star, When
- from django.db.models.fields import DecimalField, FloatField, IntegerField
-
- __all__ = [
- 'Aggregate', 'Avg', 'Count', 'Max', 'Min', 'StdDev', 'Sum', 'Variance',
- ]
-
-
- class Aggregate(Func):
- contains_aggregate = True
- name = None
- filter_template = '%s FILTER (WHERE %%(filter)s)'
- window_compatible = True
-
- def __init__(self, *args, filter=None, **kwargs):
- self.filter = filter
- super().__init__(*args, **kwargs)
-
- def get_source_fields(self):
- # Don't return the filter expression since it's not a source field.
- return [e._output_field_or_none for e in super().get_source_expressions()]
-
- def get_source_expressions(self):
- source_expressions = super().get_source_expressions()
- if self.filter:
- source_expressions += [self.filter]
- return source_expressions
-
- def set_source_expressions(self, exprs):
- self.filter = self.filter and exprs.pop()
- return super().set_source_expressions(exprs)
-
- def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False):
- # Aggregates are not allowed in UPDATE queries, so ignore for_save
- c = super().resolve_expression(query, allow_joins, reuse, summarize)
- c.filter = c.filter and c.filter.resolve_expression(query, allow_joins, reuse, summarize)
- if not summarize:
- # Call Aggregate.get_source_expressions() to avoid
- # returning self.filter and including that in this loop.
- expressions = super(Aggregate, c).get_source_expressions()
- for index, expr in enumerate(expressions):
- if expr.contains_aggregate:
- before_resolved = self.get_source_expressions()[index]
- name = before_resolved.name if hasattr(before_resolved, 'name') else repr(before_resolved)
- raise FieldError("Cannot compute %s('%s'): '%s' is an aggregate" % (c.name, name, name))
- return c
-
- @property
- def default_alias(self):
- expressions = self.get_source_expressions()
- if len(expressions) == 1 and hasattr(expressions[0], 'name'):
- return '%s__%s' % (expressions[0].name, self.name.lower())
- raise TypeError("Complex expressions require an alias")
-
- def get_group_by_cols(self):
- return []
-
- def as_sql(self, compiler, connection, **extra_context):
- if self.filter:
- if connection.features.supports_aggregate_filter_clause:
- filter_sql, filter_params = self.filter.as_sql(compiler, connection)
- template = self.filter_template % extra_context.get('template', self.template)
- sql, params = super().as_sql(compiler, connection, template=template, filter=filter_sql)
- return sql, params + filter_params
- else:
- copy = self.copy()
- copy.filter = None
- source_expressions = copy.get_source_expressions()
- condition = When(self.filter, then=source_expressions[0])
- copy.set_source_expressions([Case(condition)] + source_expressions[1:])
- return super(Aggregate, copy).as_sql(compiler, connection, **extra_context)
- return super().as_sql(compiler, connection, **extra_context)
-
- def _get_repr_options(self):
- options = super()._get_repr_options()
- if self.filter:
- options.update({'filter': self.filter})
- return options
-
-
- class Avg(Aggregate):
- function = 'AVG'
- name = 'Avg'
-
- def _resolve_output_field(self):
- source_field = self.get_source_fields()[0]
- if isinstance(source_field, (IntegerField, DecimalField)):
- return FloatField()
- return super()._resolve_output_field()
-
- def as_mysql(self, compiler, connection):
- sql, params = super().as_sql(compiler, connection)
- if self.output_field.get_internal_type() == 'DurationField':
- sql = 'CAST(%s as SIGNED)' % sql
- return sql, params
-
- def as_oracle(self, compiler, connection):
- if self.output_field.get_internal_type() == 'DurationField':
- expression = self.get_source_expressions()[0]
- from django.db.backends.oracle.functions import IntervalToSeconds, SecondsToInterval
- return compiler.compile(
- SecondsToInterval(Avg(IntervalToSeconds(expression), filter=self.filter))
- )
- return super().as_sql(compiler, connection)
-
-
- class Count(Aggregate):
- function = 'COUNT'
- name = 'Count'
- template = '%(function)s(%(distinct)s%(expressions)s)'
- output_field = IntegerField()
-
- def __init__(self, expression, distinct=False, filter=None, **extra):
- if expression == '*':
- expression = Star()
- if isinstance(expression, Star) and filter is not None:
- raise ValueError('Star cannot be used with filter. Please specify a field.')
- super().__init__(
- expression, distinct='DISTINCT ' if distinct else '',
- filter=filter, **extra
- )
-
- def _get_repr_options(self):
- return {**super()._get_repr_options(), 'distinct': self.extra['distinct'] != ''}
-
- def convert_value(self, value, expression, connection):
- return 0 if value is None else value
-
-
- class Max(Aggregate):
- function = 'MAX'
- name = 'Max'
-
-
- class Min(Aggregate):
- function = 'MIN'
- name = 'Min'
-
-
- class StdDev(Aggregate):
- name = 'StdDev'
- output_field = FloatField()
-
- def __init__(self, expression, sample=False, **extra):
- self.function = 'STDDEV_SAMP' if sample else 'STDDEV_POP'
- super().__init__(expression, **extra)
-
- def _get_repr_options(self):
- return {**super()._get_repr_options(), 'sample': self.function == 'STDDEV_SAMP'}
-
-
- class Sum(Aggregate):
- function = 'SUM'
- name = 'Sum'
-
- def as_mysql(self, compiler, connection):
- sql, params = super().as_sql(compiler, connection)
- if self.output_field.get_internal_type() == 'DurationField':
- sql = 'CAST(%s as SIGNED)' % sql
- return sql, params
-
- def as_oracle(self, compiler, connection):
- if self.output_field.get_internal_type() == 'DurationField':
- expression = self.get_source_expressions()[0]
- from django.db.backends.oracle.functions import IntervalToSeconds, SecondsToInterval
- return compiler.compile(
- SecondsToInterval(Sum(IntervalToSeconds(expression)))
- )
- return super().as_sql(compiler, connection)
-
-
- class Variance(Aggregate):
- name = 'Variance'
- output_field = FloatField()
-
- def __init__(self, expression, sample=False, **extra):
- self.function = 'VAR_SAMP' if sample else 'VAR_POP'
- super().__init__(expression, **extra)
-
- def _get_repr_options(self):
- return {**super()._get_repr_options(), 'sample': self.function == 'VAR_SAMP'}
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