django.db.models.aggregates のソースコード
"""
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',
]
[ドキュメント]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
[ドキュメント]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)
[ドキュメント]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
[ドキュメント]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'}
[ドキュメント]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)
[ドキュメント]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'}
