196 lines
6.8 KiB
Python
196 lines
6.8 KiB
Python
|
"""
|
||
|
|
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 IntegerField
|
||
|
|
from django.db.models.functions.comparison import Coalesce
|
||
|
|
from django.db.models.functions.mixins import (
|
||
|
|
FixDurationInputMixin,
|
||
|
|
NumericOutputFieldMixin,
|
||
|
|
)
|
||
|
|
|
||
|
|
__all__ = [
|
||
|
|
"Aggregate",
|
||
|
|
"Avg",
|
||
|
|
"Count",
|
||
|
|
"Max",
|
||
|
|
"Min",
|
||
|
|
"StdDev",
|
||
|
|
"Sum",
|
||
|
|
"Variance",
|
||
|
|
]
|
||
|
|
|
||
|
|
|
||
|
|
class Aggregate(Func):
|
||
|
|
template = "%(function)s(%(distinct)s%(expressions)s)"
|
||
|
|
contains_aggregate = True
|
||
|
|
name = None
|
||
|
|
filter_template = "%s FILTER (WHERE %%(filter)s)"
|
||
|
|
window_compatible = True
|
||
|
|
allow_distinct = False
|
||
|
|
empty_result_set_value = None
|
||
|
|
|
||
|
|
def __init__(
|
||
|
|
self, *expressions, distinct=False, filter=None, default=None, **extra
|
||
|
|
):
|
||
|
|
if distinct and not self.allow_distinct:
|
||
|
|
raise TypeError("%s does not allow distinct." % self.__class__.__name__)
|
||
|
|
if default is not None and self.empty_result_set_value is not None:
|
||
|
|
raise TypeError(f"{self.__class__.__name__} does not allow default.")
|
||
|
|
self.distinct = distinct
|
||
|
|
self.filter = filter
|
||
|
|
self.default = default
|
||
|
|
super().__init__(*expressions, **extra)
|
||
|
|
|
||
|
|
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:
|
||
|
|
return 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)
|
||
|
|
)
|
||
|
|
if (default := c.default) is None:
|
||
|
|
return c
|
||
|
|
if hasattr(default, "resolve_expression"):
|
||
|
|
default = default.resolve_expression(query, allow_joins, reuse, summarize)
|
||
|
|
c.default = None # Reset the default argument before wrapping.
|
||
|
|
coalesce = Coalesce(c, default, output_field=c._output_field_or_none)
|
||
|
|
coalesce.is_summary = c.is_summary
|
||
|
|
return coalesce
|
||
|
|
|
||
|
|
@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, alias=None):
|
||
|
|
return []
|
||
|
|
|
||
|
|
def as_sql(self, compiler, connection, **extra_context):
|
||
|
|
extra_context["distinct"] = "DISTINCT " if self.distinct else ""
|
||
|
|
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,
|
||
|
|
**extra_context,
|
||
|
|
)
|
||
|
|
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.distinct:
|
||
|
|
options["distinct"] = self.distinct
|
||
|
|
if self.filter:
|
||
|
|
options["filter"] = self.filter
|
||
|
|
return options
|
||
|
|
|
||
|
|
|
||
|
|
class Avg(FixDurationInputMixin, NumericOutputFieldMixin, Aggregate):
|
||
|
|
function = "AVG"
|
||
|
|
name = "Avg"
|
||
|
|
allow_distinct = True
|
||
|
|
|
||
|
|
|
||
|
|
class Count(Aggregate):
|
||
|
|
function = "COUNT"
|
||
|
|
name = "Count"
|
||
|
|
output_field = IntegerField()
|
||
|
|
allow_distinct = True
|
||
|
|
empty_result_set_value = 0
|
||
|
|
|
||
|
|
def __init__(self, expression, 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, filter=filter, **extra)
|
||
|
|
|
||
|
|
|
||
|
|
class Max(Aggregate):
|
||
|
|
function = "MAX"
|
||
|
|
name = "Max"
|
||
|
|
|
||
|
|
|
||
|
|
class Min(Aggregate):
|
||
|
|
function = "MIN"
|
||
|
|
name = "Min"
|
||
|
|
|
||
|
|
|
||
|
|
class StdDev(NumericOutputFieldMixin, Aggregate):
|
||
|
|
name = "StdDev"
|
||
|
|
|
||
|
|
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(FixDurationInputMixin, Aggregate):
|
||
|
|
function = "SUM"
|
||
|
|
name = "Sum"
|
||
|
|
allow_distinct = True
|
||
|
|
|
||
|
|
|
||
|
|
class Variance(NumericOutputFieldMixin, Aggregate):
|
||
|
|
name = "Variance"
|
||
|
|
|
||
|
|
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"}
|