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1 import copy |
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2 |
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3 from django.db.models.query import QuerySet, EmptyQuerySet, insert_query |
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4 from django.dispatch import dispatcher |
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5 from django.db.models import signals |
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6 from django.db.models.fields import FieldDoesNotExist |
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7 |
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8 def ensure_default_manager(sender): |
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9 cls = sender |
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10 if not getattr(cls, '_default_manager', None) and not cls._meta.abstract: |
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11 # Create the default manager, if needed. |
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12 try: |
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13 cls._meta.get_field('objects') |
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14 raise ValueError, "Model %s must specify a custom Manager, because it has a field named 'objects'" % cls.__name__ |
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15 except FieldDoesNotExist: |
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16 pass |
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17 cls.add_to_class('objects', Manager()) |
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18 |
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19 dispatcher.connect(ensure_default_manager, signal=signals.class_prepared) |
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20 |
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21 class Manager(object): |
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22 # Tracks each time a Manager instance is created. Used to retain order. |
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23 creation_counter = 0 |
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24 |
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25 def __init__(self): |
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26 super(Manager, self).__init__() |
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27 # Increase the creation counter, and save our local copy. |
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28 self.creation_counter = Manager.creation_counter |
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29 Manager.creation_counter += 1 |
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30 self.model = None |
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31 |
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32 def contribute_to_class(self, model, name): |
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33 # TODO: Use weakref because of possible memory leak / circular reference. |
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34 self.model = model |
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35 setattr(model, name, ManagerDescriptor(self)) |
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36 if not getattr(model, '_default_manager', None) or self.creation_counter < model._default_manager.creation_counter: |
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37 model._default_manager = self |
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38 |
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39 def _copy_to_model(self, model): |
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40 """ |
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41 Makes a copy of the manager and assigns it to 'model', which should be |
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42 a child of the existing model (used when inheriting a manager from an |
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43 abstract base class). |
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44 """ |
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45 assert issubclass(model, self.model) |
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46 mgr = copy.copy(self) |
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47 mgr.model = model |
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48 return mgr |
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49 |
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50 ####################### |
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51 # PROXIES TO QUERYSET # |
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52 ####################### |
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53 |
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54 def get_empty_query_set(self): |
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55 return EmptyQuerySet(self.model) |
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56 |
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57 def get_query_set(self): |
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58 """Returns a new QuerySet object. Subclasses can override this method |
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59 to easily customize the behavior of the Manager. |
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60 """ |
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61 return QuerySet(self.model) |
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62 |
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63 def none(self): |
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64 return self.get_empty_query_set() |
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65 |
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66 def all(self): |
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67 return self.get_query_set() |
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68 |
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69 def count(self): |
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70 return self.get_query_set().count() |
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71 |
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72 def dates(self, *args, **kwargs): |
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73 return self.get_query_set().dates(*args, **kwargs) |
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74 |
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75 def distinct(self, *args, **kwargs): |
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76 return self.get_query_set().distinct(*args, **kwargs) |
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77 |
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78 def extra(self, *args, **kwargs): |
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79 return self.get_query_set().extra(*args, **kwargs) |
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80 |
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81 def get(self, *args, **kwargs): |
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82 return self.get_query_set().get(*args, **kwargs) |
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83 |
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84 def get_or_create(self, **kwargs): |
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85 return self.get_query_set().get_or_create(**kwargs) |
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86 |
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87 def create(self, **kwargs): |
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88 return self.get_query_set().create(**kwargs) |
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89 |
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90 def filter(self, *args, **kwargs): |
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91 return self.get_query_set().filter(*args, **kwargs) |
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92 |
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93 def complex_filter(self, *args, **kwargs): |
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94 return self.get_query_set().complex_filter(*args, **kwargs) |
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95 |
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96 def exclude(self, *args, **kwargs): |
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97 return self.get_query_set().exclude(*args, **kwargs) |
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98 |
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99 def in_bulk(self, *args, **kwargs): |
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100 return self.get_query_set().in_bulk(*args, **kwargs) |
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101 |
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102 def iterator(self, *args, **kwargs): |
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103 return self.get_query_set().iterator(*args, **kwargs) |
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104 |
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105 def latest(self, *args, **kwargs): |
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106 return self.get_query_set().latest(*args, **kwargs) |
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107 |
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108 def order_by(self, *args, **kwargs): |
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109 return self.get_query_set().order_by(*args, **kwargs) |
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110 |
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111 def select_related(self, *args, **kwargs): |
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112 return self.get_query_set().select_related(*args, **kwargs) |
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113 |
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114 def values(self, *args, **kwargs): |
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115 return self.get_query_set().values(*args, **kwargs) |
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116 |
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117 def values_list(self, *args, **kwargs): |
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118 return self.get_query_set().values_list(*args, **kwargs) |
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119 |
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120 def update(self, *args, **kwargs): |
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121 return self.get_query_set().update(*args, **kwargs) |
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122 |
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123 def reverse(self, *args, **kwargs): |
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124 return self.get_query_set().reverse(*args, **kwargs) |
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125 |
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126 def _insert(self, values, **kwargs): |
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127 return insert_query(self.model, values, **kwargs) |
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128 |
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129 def _update(self, values, **kwargs): |
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130 return self.get_query_set()._update(values, **kwargs) |
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131 |
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132 class ManagerDescriptor(object): |
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133 # This class ensures managers aren't accessible via model instances. |
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134 # For example, Poll.objects works, but poll_obj.objects raises AttributeError. |
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135 def __init__(self, manager): |
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136 self.manager = manager |
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137 |
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138 def __get__(self, instance, type=None): |
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139 if instance != None: |
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140 raise AttributeError, "Manager isn't accessible via %s instances" % type.__name__ |
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141 return self.manager |
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142 |
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143 class EmptyManager(Manager): |
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144 def get_query_set(self): |
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145 return self.get_empty_query_set() |