# orm/identity.py
# Copyright (C) 2005-2021 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
import weakref
from . import attributes
from . import util as orm_util
from .. import exc as sa_exc
from .. import util
class IdentityMap(object):
def __init__(self):
self._dict = {}
self._modified = set()
self._wr = weakref.ref(self)
def keys(self):
return self._dict.keys()
def replace(self, state):
raise NotImplementedError()
def add(self, state):
raise NotImplementedError()
def _add_unpresent(self, state, key):
"""optional inlined form of add() which can assume item isn't present
in the map"""
self.add(state)
def update(self, dict_):
raise NotImplementedError("IdentityMap uses add() to insert data")
def clear(self):
raise NotImplementedError("IdentityMap uses remove() to remove data")
def _manage_incoming_state(self, state):
state._instance_dict = self._wr
if state.modified:
self._modified.add(state)
def _manage_removed_state(self, state):
del state._instance_dict
if state.modified:
self._modified.discard(state)
def _dirty_states(self):
return self._modified
def check_modified(self):
"""return True if any InstanceStates present have been marked
as 'modified'.
"""
return bool(self._modified)
def has_key(self, key):
return key in self
def popitem(self):
raise NotImplementedError("IdentityMap uses remove() to remove data")
def pop(self, key, *args):
raise NotImplementedError("IdentityMap uses remove() to remove data")
def setdefault(self, key, default=None):
raise NotImplementedError("IdentityMap uses add() to insert data")
def __len__(self):
return len(self._dict)
def copy(self):
raise NotImplementedError()
def __setitem__(self, key, value):
raise NotImplementedError("IdentityMap uses add() to insert data")
def __delitem__(self, key):
raise NotImplementedError("IdentityMap uses remove() to remove data")
class WeakInstanceDict(IdentityMap):
def __getitem__(self, key):
state = self._dict[key]
o = state.obj()
if o is None:
raise KeyError(key)
return o
def __contains__(self, key):
try:
if key in self._dict:
state = self._dict[key]
o = state.obj()
else:
return False
except KeyError:
return False
else:
return o is not None
def contains_state(self, state):
if state.key in self._dict:
try:
return self._dict[state.key] is state
except KeyError:
return False
else:
return False
def replace(self, state):
if state.key in self._dict:
try:
existing = self._dict[state.key]
except KeyError:
# catch gc removed the key after we just checked for it
pass
else:
if existing is not state:
self._manage_removed_state(existing)
else:
return None
else:
existing = None
self._dict[state.key] = state
self._manage_incoming_state(state)
return existing
def add(self, state):
key = state.key
# inline of self.__contains__
if key in self._dict:
try:
existing_state = self._dict[key]
except KeyError:
# catch gc removed the key after we just checked for it
pass
else:
if existing_state is not state:
o = existing_state.obj()
if o is not None:
raise sa_exc.InvalidRequestError(
"Can't attach instance "
"%s; another instance with key %s is already "
"present in this session."
% (orm_util.state_str(state), state.key)
)
else:
return False
self._dict[key] = state
self._manage_incoming_state(state)
return True
def _add_unpresent(self, state, key):
# inlined form of add() called by loading.py
self._dict[key] = state
state._instance_dict = self._wr
def get(self, key, default=None):
if key not in self._dict:
return default
try:
state = self._dict[key]
except KeyError:
# catch gc removed the key after we just checked for it
return default
else:
o = state.obj()
if o is None:
return default
return o
def items(self):
values = self.all_states()
result = []
for state in values:
value = state.obj()
if value is not None:
result.append((state.key, value))
return result
def values(self):
values = self.all_states()
result = []
for state in values:
value = state.obj()
if value is not None:
result.append(value)
return result
def __iter__(self):
return iter(self.keys())
if util.py2k:
def iteritems(self):
return iter(self.items())
def itervalues(self):
return iter(self.values())
def all_states(self):
if util.py2k:
return self._dict.values()
else:
return list(self._dict.values())
def _fast_discard(self, state):
# used by InstanceState for state being
# GC'ed, inlines _managed_removed_state
try:
st = self._dict[state.key]
except KeyError:
# catch gc removed the key after we just checked for it
pass
else:
if st is state:
self._dict.pop(state.key, None)
def discard(self, state):
self.safe_discard(state)
def safe_discard(self, state):
if state.key in self._dict:
try:
st = self._dict[state.key]
except KeyError:
# catch gc removed the key after we just checked for it
pass
else:
if st is state:
self._dict.pop(state.key, None)
self._manage_removed_state(state)
def prune(self):
return 0
class StrongInstanceDict(IdentityMap):
"""A 'strong-referencing' version of the identity map.
.. deprecated 1.1::
The strong
reference identity map is legacy. See the
recipe at :ref:`session_referencing_behavior` for
an event-based approach to maintaining strong identity
references.
"""
if util.py2k:
def itervalues(self):
return self._dict.itervalues()
def iteritems(self):
return self._dict.iteritems()
def __iter__(self):
return iter(self.dict_)
def __getitem__(self, key):
return self._dict[key]
def __contains__(self, key):
return key in self._dict
def get(self, key, default=None):
return self._dict.get(key, default)
def values(self):
return self._dict.values()
def items(self):
return self._dict.items()
def all_states(self):
return [attributes.instance_state(o) for o in self.values()]
def contains_state(self, state):
return (
state.key in self
and attributes.instance_state(self[state.key]) is state
)
def replace(self, state):
if state.key in self._dict:
existing = self._dict[state.key]
existing = attributes.instance_state(existing)
if existing is not state:
self._manage_removed_state(existing)
else:
return
else:
existing = None
self._dict[state.key] = state.obj()
self._manage_incoming_state(state)
return existing
def add(self, state):
if state.key in self:
if attributes.instance_state(self._dict[state.key]) is not state:
raise sa_exc.InvalidRequestError(
"Can't attach instance "
"%s; another instance with key %s is already "
"present in this session."
% (orm_util.state_str(state), state.key)
)
return False
else:
self._dict[state.key] = state.obj()
self._manage_incoming_state(state)
return True
def _add_unpresent(self, state, key):
# inlined form of add() called by loading.py
self._dict[key] = state.obj()
state._instance_dict = self._wr
def _fast_discard(self, state):
# used by InstanceState for state being
# GC'ed, inlines _managed_removed_state
try:
obj = self._dict[state.key]
except KeyError:
# catch gc removed the key after we just checked for it
pass
else:
if attributes.instance_state(obj) is state:
self._dict.pop(state.key, None)
def discard(self, state):
self.safe_discard(state)
def safe_discard(self, state):
if state.key in self._dict:
obj = self._dict[state.key]
st = attributes.instance_state(obj)
if st is state:
self._dict.pop(state.key, None)
self._manage_removed_state(state)
def prune(self):
"""prune unreferenced, non-dirty states."""
ref_count = len(self)
dirty = [s.obj() for s in self.all_states() if s.modified]
# work around http://bugs.python.org/issue6149
keepers = weakref.WeakValueDictionary()
keepers.update(self)
self._dict.clear()
self._dict.update(keepers)
self.modified = bool(dirty)
return ref_count - len(self)
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