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from django.db import connections
from django.db.models import Manager
from django.db.models.query import QuerySet
from django.db.models.sql.compiler import SQLCompiler
from django.db.models.sql.query import Query
from django.db.models.sql.where import WhereNode
class GroupedCompiler(SQLCompiler):
def get_group_by(self, select, order_by):
result = super(GroupedCompiler, self).get_group_by(select, order_by)
expressions = []
for expr in self.query.real_group_by:
ref = expr if hasattr(expr, "as_sql") else self.query.resolve_ref(expr)
sql, params = self.compile(ref)
result.append((sql, params))
return result
class GroupedQuery(Query):
def __init__(self, model, where=WhereNode):
super(GroupedQuery, self).__init__(model, where)
self.real_group_by = []
def clone(self, klass=None, memo=None, **kwargs):
obj = super(GroupedQuery, self).clone(klass, memo, **kwargs)
obj.real_group_by = self.real_group_by[:]
return obj
def add_grouping(self, *grouping):
self.real_group_by.extend(grouping)
def clear_grouping(self):
self.real_group_by = []
def get_compiler(self, using=None, connection=None):
if using is None and connection is None:
raise ValueError("Need either using or connection")
if using:
connection = connections[using]
return GroupedCompiler(self, connection, using)
class GroupedQuerySet(QuerySet):
def __init__(self, model=None, query=None, using=None, hints=None):
super(GroupedQuerySet, self).__init__(model, query, using, hints)
self.query = query or GroupedQuery(self.model)
def group_by(self, *field_names):
obj = self._clone()
obj.query.clear_grouping()
obj.query.add_grouping(*field_names)
return obj
class GroupedManager(Manager):
def __init__(self):
super(GroupedManager, self).__init__()
self._queryset_class = GroupedQuerySet
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