django1/django/db/models/query_utils.py

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"""
Various data structures used in query construction.
Factored out from django.db.models.query to avoid making the main module very
large and/or so that they can be used by other modules without getting into
circular import difficulties.
"""
from __future__ import unicode_literals
from django.apps import apps
from django.db.backends import utils
from django.utils import six
from django.utils import tree
class InvalidQuery(Exception):
"""
The query passed to raw isn't a safe query to use with raw.
"""
pass
class QueryWrapper(object):
"""
A type that indicates the contents are an SQL fragment and the associate
parameters. Can be used to pass opaque data to a where-clause, for example.
"""
def __init__(self, sql, params):
Fixed #17260 -- Added time zone aware aggregation and lookups. Thanks Carl Meyer for the review. Squashed commit of the following: commit 4f290bdb60b7d8534abf4ca901bd0844612dcbda Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Wed Feb 13 21:21:30 2013 +0100 Used '0:00' instead of 'UTC' which doesn't always exist in Oracle. Thanks Ian Kelly for the suggestion. commit 01b6366f3ce67d57a58ca8f25e5be77911748638 Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Wed Feb 13 13:38:43 2013 +0100 Made tzname a parameter of datetime_extract/trunc_sql. This is required to work around a bug in Oracle. commit 924a144ef8a80ba4daeeafbe9efaa826566e9d02 Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Wed Feb 13 14:47:44 2013 +0100 Added support for parameters in SELECT clauses. commit b4351d2890cd1090d3ff2d203fe148937324c935 Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Mon Feb 11 22:30:22 2013 +0100 Documented backwards incompatibilities in the two previous commits. commit 91ef84713c81bd455f559dacf790e586d08cacb9 Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Mon Feb 11 09:42:31 2013 +0100 Used QuerySet.datetimes for the admin's date_hierarchy. commit 0d0de288a5210fa106cd4350961eb2006535cc5c Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Mon Feb 11 09:29:38 2013 +0100 Used QuerySet.datetimes in date-based generic views. commit 9c0859ff7c0b00734afe7fc15609d43d83215072 Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Sun Feb 10 21:43:25 2013 +0100 Implemented QuerySet.datetimes on Oracle. commit 68ab511a4ffbd2b811bf5da174d47e4dd90f28fc Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Sun Feb 10 21:43:14 2013 +0100 Implemented QuerySet.datetimes on MySQL. commit 22d52681d347a8cdf568dc31ed032cbc61d049ef Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Sun Feb 10 21:42:29 2013 +0100 Implemented QuerySet.datetimes on SQLite. commit f6800fd04c93722b45f9236976389e0b2fe436f5 Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Sun Feb 10 21:43:03 2013 +0100 Implemented QuerySet.datetimes on PostgreSQL. commit 0c829c23f4cf4d6804cadcc93032dd4c26b8c65e Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Sun Feb 10 21:41:08 2013 +0100 Added datetime-handling infrastructure in the ORM layers. commit 104d82a7778cf3f0f5d03dfa53709c26df45daad Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Mon Feb 11 10:05:55 2013 +0100 Updated null_queries tests to avoid clashing with the __second lookup. commit c01bbb32358201b3ac8cb4291ef87b7612a2b8e6 Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Sun Feb 10 23:07:41 2013 +0100 Updated tests of .dates(). Replaced .dates() by .datetimes() for DateTimeFields. Replaced dates with datetimes in the expected output for DateFields. commit 50fb7a52462fecf0127b38e7f3df322aeb287c43 Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Sun Feb 10 21:40:09 2013 +0100 Updated and added tests for QuerySet.datetimes. commit a8451a5004c437190e264667b1e6fb8acc3c1eeb Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Sun Feb 10 22:34:46 2013 +0100 Documented the new time lookups and updated the date lookups. commit 29413eab2bd1d5e004598900c0dadc0521bbf4d3 Author: Aymeric Augustin <aymeric.augustin@m4x.org> Date: Sun Feb 10 16:15:49 2013 +0100 Documented QuerySet.datetimes and updated QuerySet.dates.
2013-02-10 23:15:49 +08:00
self.data = sql, list(params)
def as_sql(self, qn=None, connection=None):
return self.data
class Q(tree.Node):
"""
Encapsulates filters as objects that can then be combined logically (using
& and |).
"""
# Connection types
AND = 'AND'
OR = 'OR'
default = AND
def __init__(self, *args, **kwargs):
super(Q, self).__init__(children=list(args) + list(six.iteritems(kwargs)))
def _combine(self, other, conn):
if not isinstance(other, Q):
raise TypeError(other)
obj = type(self)()
obj.connector = conn
obj.add(self, conn)
obj.add(other, conn)
return obj
def __or__(self, other):
return self._combine(other, self.OR)
def __and__(self, other):
return self._combine(other, self.AND)
def __invert__(self):
obj = type(self)()
obj.add(self, self.AND)
obj.negate()
return obj
def clone(self):
clone = self.__class__._new_instance(
children=[], connector=self.connector, negated=self.negated)
for child in self.children:
if hasattr(child, 'clone'):
clone.children.append(child.clone())
else:
clone.children.append(child)
return clone
class DeferredAttribute(object):
"""
A wrapper for a deferred-loading field. When the value is read from this
object the first time, the query is executed.
"""
def __init__(self, field_name, model):
self.field_name = field_name
def __get__(self, instance, owner):
"""
Retrieves and caches the value from the datastore on the first lookup.
Returns the cached value.
"""
from django.db.models.fields import FieldDoesNotExist
non_deferred_model = instance._meta.proxy_for_model
opts = non_deferred_model._meta
assert instance is not None
data = instance.__dict__
if data.get(self.field_name, self) is self:
# self.field_name is the attname of the field, but only() takes the
# actual name, so we need to translate it here.
try:
f = opts.get_field_by_name(self.field_name)[0]
except FieldDoesNotExist:
f = [f for f in opts.fields if f.attname == self.field_name][0]
name = f.name
# Let's see if the field is part of the parent chain. If so we
# might be able to reuse the already loaded value. Refs #18343.
val = self._check_parent_chain(instance, name)
if val is None:
# We use only() instead of values() here because we want the
# various data coercion methods (to_python(), etc.) to be
# called here.
val = getattr(
non_deferred_model._base_manager.only(name).using(
instance._state.db).get(pk=instance.pk),
self.field_name
)
data[self.field_name] = val
return data[self.field_name]
def __set__(self, instance, value):
"""
Deferred loading attributes can be set normally (which means there will
never be a database lookup involved.
"""
instance.__dict__[self.field_name] = value
def _check_parent_chain(self, instance, name):
"""
Check if the field value can be fetched from a parent field already
loaded in the instance. This can be done if the to-be fetched
field is a primary key field.
"""
opts = instance._meta
f = opts.get_field_by_name(name)[0]
link_field = opts.get_ancestor_link(f.model)
if f.primary_key and f != link_field:
return getattr(instance, link_field.attname)
return None
def select_related_descend(field, restricted, requested, load_fields, reverse=False):
"""
Returns True if this field should be used to descend deeper for
select_related() purposes. Used by both the query construction code
(sql.query.fill_related_selections()) and the model instance creation code
(query.get_klass_info()).
Arguments:
* field - the field to be checked
* restricted - a boolean field, indicating if the field list has been
manually restricted using a requested clause)
* requested - The select_related() dictionary.
* load_fields - the set of fields to be loaded on this model
* reverse - boolean, True if we are checking a reverse select related
"""
if not field.rel:
return False
if field.rel.parent_link and not reverse:
return False
if restricted:
if reverse and field.related_query_name() not in requested:
return False
if not reverse and field.name not in requested:
return False
if not restricted and field.null:
return False
if load_fields:
if field.name not in load_fields:
if restricted and field.name in requested:
raise InvalidQuery("Field %s.%s cannot be both deferred"
" and traversed using select_related"
" at the same time." %
(field.model._meta.object_name, field.name))
return False
return True
# This function is needed because data descriptors must be defined on a class
# object, not an instance, to have any effect.
def deferred_class_factory(model, attrs):
"""
Returns a class object that is a copy of "model" with the specified "attrs"
being replaced with DeferredAttribute objects. The "pk_value" ties the
deferred attributes to a particular instance of the model.
"""
if not attrs:
return model
# Never create deferred models based on deferred model
if model._deferred:
# Deferred models are proxies for the non-deferred model. We never
# create chains of defers => proxy_for_model is the non-deferred
# model.
model = model._meta.proxy_for_model
# The app registry wants a unique name for each model, otherwise the new
# class won't be created (we get an exception). Therefore, we generate
# the name using the passed in attrs. It's OK to reuse an existing class
# object if the attrs are identical.
name = "%s_Deferred_%s" % (model.__name__, '_'.join(sorted(list(attrs))))
name = utils.truncate_name(name, 80, 32)
try:
return apps.get_model(model._meta.app_label, name)
except LookupError:
class Meta:
proxy = True
app_label = model._meta.app_label
overrides = dict((attr, DeferredAttribute(attr, model)) for attr in attrs)
overrides["Meta"] = Meta
overrides["__module__"] = model.__module__
overrides["_deferred"] = True
return type(str(name), (model,), overrides)
# The above function is also used to unpickle model instances with deferred
# fields.
deferred_class_factory.__safe_for_unpickling__ = True