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Fixed #19635 -- Made fields pickleable
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@ -10,6 +10,7 @@ from base64 import b64decode, b64encode
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from itertools import tee
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from django.db import connection
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from django.db.models.loading import get_model
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from django.db.models.query_utils import QueryWrapper
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from django.conf import settings
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from django import forms
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@ -24,6 +25,9 @@ from django.utils.encoding import smart_text, force_text, force_bytes
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from django.utils.ipv6 import clean_ipv6_address
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from django.utils import six
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class Empty(object):
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pass
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class NOT_PROVIDED:
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pass
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@ -31,6 +35,9 @@ class NOT_PROVIDED:
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# of most "choices" lists.
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BLANK_CHOICE_DASH = [("", "---------")]
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def _load_field(app_label, model_name, field_name):
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return get_model(app_label, model_name)._meta.get_field_by_name(field_name)[0]
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class FieldDoesNotExist(Exception):
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pass
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@ -49,6 +56,11 @@ class FieldDoesNotExist(Exception):
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#
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# getattr(obj, opts.pk.attname)
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def _empty(of_cls):
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new = Empty()
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new.__class__ = of_cls
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return new
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@total_ordering
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class Field(object):
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"""Base class for all field types"""
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@ -148,6 +160,34 @@ class Field(object):
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memodict[id(self)] = obj
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return obj
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def __copy__(self):
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# We need to avoid hitting __reduce__, so define this
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# slightly weird copy construct.
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obj = Empty()
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obj.__class__ = self.__class__
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obj.__dict__ = self.__dict__.copy()
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return obj
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def __reduce__(self):
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"""
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Pickling should return the model._meta.fields instance of the field,
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not a new copy of that field. So, we use the app cache to load the
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model and then the field back.
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"""
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if not hasattr(self, 'model'):
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# Fields are sometimes used without attaching them to models (for
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# example in aggregation). In this case give back a plain field
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# instance. The code below will create a new empty instance of
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# class self.__class__, then update its dict with self.__dict__
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# values - so, this is very close to normal pickle.
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return _empty, (self.__class__,), self.__dict__
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if self.model._deferred:
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# Deferred model will not be found from the app cache. This could
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# be fixed by reconstructing the deferred model on unpickle.
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raise RuntimeError("Fields of deferred models can't be reduced")
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return _load_field, (self.model._meta.app_label, self.model._meta.object_name,
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self.name)
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def to_python(self, value):
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"""
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Converts the input value into the expected Python data type, raising
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@ -189,54 +189,6 @@ class Query(object):
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memo[id(self)] = result
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return result
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def __getstate__(self):
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"""
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Pickling support.
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"""
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obj_dict = self.__dict__.copy()
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obj_dict['related_select_cols'] = []
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# Fields can't be pickled, so if a field list has been
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# specified, we pickle the list of field names instead.
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# None is also a possible value; that can pass as-is
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obj_dict['select'] = [
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(s.col, s.field is not None and s.field.name or None)
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for s in obj_dict['select']
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]
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# alias_map can also contain references to fields.
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new_alias_map = {}
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for alias, join_info in obj_dict['alias_map'].items():
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if join_info.join_field is None:
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new_alias_map[alias] = join_info
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else:
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model = join_info.join_field.model._meta
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field_id = (model.app_label, model.object_name, join_info.join_field.name)
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new_alias_map[alias] = join_info._replace(join_field=field_id)
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obj_dict['alias_map'] = new_alias_map
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return obj_dict
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def __setstate__(self, obj_dict):
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"""
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Unpickling support.
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"""
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# Rebuild list of field instances
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opts = obj_dict['model']._meta
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obj_dict['select'] = [
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SelectInfo(tpl[0], tpl[1] is not None and opts.get_field(tpl[1]) or None)
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for tpl in obj_dict['select']
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]
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new_alias_map = {}
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for alias, join_info in obj_dict['alias_map'].items():
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if join_info.join_field is None:
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new_alias_map[alias] = join_info
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else:
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field_id = join_info.join_field
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new_alias_map[alias] = join_info._replace(
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join_field=get_model(field_id[0], field_id[1])._meta.get_field(field_id[2]))
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obj_dict['alias_map'] = new_alias_map
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self.__dict__.update(obj_dict)
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def prepare(self):
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return self
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@ -345,30 +345,6 @@ class Constraint(object):
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def __init__(self, alias, col, field):
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self.alias, self.col, self.field = alias, col, field
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def __getstate__(self):
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"""Save the state of the Constraint for pickling.
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Fields aren't necessarily pickleable, because they can have
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callable default values. So, instead of pickling the field
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store a reference so we can restore it manually
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"""
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obj_dict = self.__dict__.copy()
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if self.field:
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obj_dict['model'] = self.field.model
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obj_dict['field_name'] = self.field.name
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del obj_dict['field']
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return obj_dict
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def __setstate__(self, data):
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"""Restore the constraint """
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model = data.pop('model', None)
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field_name = data.pop('field_name', None)
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self.__dict__.update(data)
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if model is not None:
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self.field = model._meta.get_field(field_name)
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else:
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self.field = None
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def prepare(self, lookup_type, value):
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if self.field:
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return self.field.get_prep_lookup(lookup_type, value)
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