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457 lines
13 KiB
Python
457 lines
13 KiB
Python
# orm/base.py
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# Copyright (C) 2005-2014 the SQLAlchemy authors and contributors <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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"""Constants and rudimental functions used throughout the ORM.
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"""
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from .. import util, inspection, exc as sa_exc
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from ..sql import expression
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from . import exc
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import operator
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PASSIVE_NO_RESULT = util.symbol('PASSIVE_NO_RESULT',
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"""Symbol returned by a loader callable or other attribute/history
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retrieval operation when a value could not be determined, based
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on loader callable flags.
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"""
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)
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ATTR_WAS_SET = util.symbol('ATTR_WAS_SET',
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"""Symbol returned by a loader callable to indicate the
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retrieved value, or values, were assigned to their attributes
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on the target object.
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""")
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ATTR_EMPTY = util.symbol('ATTR_EMPTY',
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"""Symbol used internally to indicate an attribute had no callable.
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""")
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NO_VALUE = util.symbol('NO_VALUE',
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"""Symbol which may be placed as the 'previous' value of an attribute,
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indicating no value was loaded for an attribute when it was modified,
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and flags indicated we were not to load it.
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"""
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)
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NEVER_SET = util.symbol('NEVER_SET',
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"""Symbol which may be placed as the 'previous' value of an attribute
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indicating that the attribute had not been assigned to previously.
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"""
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)
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NO_CHANGE = util.symbol("NO_CHANGE",
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"""No callables or SQL should be emitted on attribute access
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and no state should change""", canonical=0
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)
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CALLABLES_OK = util.symbol("CALLABLES_OK",
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"""Loader callables can be fired off if a value
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is not present.""", canonical=1
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)
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SQL_OK = util.symbol("SQL_OK",
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"""Loader callables can emit SQL at least on scalar value
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attributes.""", canonical=2)
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RELATED_OBJECT_OK = util.symbol("RELATED_OBJECT_OK",
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"""callables can use SQL to load related objects as well
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as scalar value attributes.
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""", canonical=4
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)
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INIT_OK = util.symbol("INIT_OK",
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"""Attributes should be initialized with a blank
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value (None or an empty collection) upon get, if no other
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value can be obtained.
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""", canonical=8
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)
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NON_PERSISTENT_OK = util.symbol("NON_PERSISTENT_OK",
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"""callables can be emitted if the parent is not persistent.""",
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canonical=16
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)
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LOAD_AGAINST_COMMITTED = util.symbol("LOAD_AGAINST_COMMITTED",
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"""callables should use committed values as primary/foreign keys during a load
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""", canonical=32
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)
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NO_AUTOFLUSH = util.symbol("NO_AUTOFLUSH",
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"""loader callables should disable autoflush.
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""", canonical=64)
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# pre-packaged sets of flags used as inputs
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PASSIVE_OFF = util.symbol("PASSIVE_OFF",
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"Callables can be emitted in all cases.",
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canonical=(RELATED_OBJECT_OK | NON_PERSISTENT_OK |
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INIT_OK | CALLABLES_OK | SQL_OK)
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)
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PASSIVE_RETURN_NEVER_SET = util.symbol("PASSIVE_RETURN_NEVER_SET",
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"""PASSIVE_OFF ^ INIT_OK""",
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canonical=PASSIVE_OFF ^ INIT_OK
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)
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PASSIVE_NO_INITIALIZE = util.symbol("PASSIVE_NO_INITIALIZE",
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"PASSIVE_RETURN_NEVER_SET ^ CALLABLES_OK",
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canonical=PASSIVE_RETURN_NEVER_SET ^ CALLABLES_OK
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)
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PASSIVE_NO_FETCH = util.symbol("PASSIVE_NO_FETCH",
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"PASSIVE_OFF ^ SQL_OK",
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canonical=PASSIVE_OFF ^ SQL_OK
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)
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PASSIVE_NO_FETCH_RELATED = util.symbol("PASSIVE_NO_FETCH_RELATED",
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"PASSIVE_OFF ^ RELATED_OBJECT_OK",
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canonical=PASSIVE_OFF ^ RELATED_OBJECT_OK
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)
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PASSIVE_ONLY_PERSISTENT = util.symbol("PASSIVE_ONLY_PERSISTENT",
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"PASSIVE_OFF ^ NON_PERSISTENT_OK",
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canonical=PASSIVE_OFF ^ NON_PERSISTENT_OK
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)
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DEFAULT_MANAGER_ATTR = '_sa_class_manager'
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DEFAULT_STATE_ATTR = '_sa_instance_state'
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_INSTRUMENTOR = ('mapper', 'instrumentor')
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EXT_CONTINUE = util.symbol('EXT_CONTINUE')
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EXT_STOP = util.symbol('EXT_STOP')
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ONETOMANY = util.symbol('ONETOMANY',
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"""Indicates the one-to-many direction for a :func:`.relationship`.
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This symbol is typically used by the internals but may be exposed within
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certain API features.
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""")
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MANYTOONE = util.symbol('MANYTOONE',
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"""Indicates the many-to-one direction for a :func:`.relationship`.
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This symbol is typically used by the internals but may be exposed within
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certain API features.
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""")
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MANYTOMANY = util.symbol('MANYTOMANY',
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"""Indicates the many-to-many direction for a :func:`.relationship`.
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This symbol is typically used by the internals but may be exposed within
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certain API features.
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""")
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NOT_EXTENSION = util.symbol('NOT_EXTENSION',
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"""Symbol indicating an :class:`_InspectionAttr` that's
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not part of sqlalchemy.ext.
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Is assigned to the :attr:`._InspectionAttr.extension_type`
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attibute.
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""")
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_none_set = frozenset([None])
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def _generative(*assertions):
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"""Mark a method as generative, e.g. method-chained."""
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@util.decorator
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def generate(fn, *args, **kw):
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self = args[0]._clone()
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for assertion in assertions:
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assertion(self, fn.__name__)
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fn(self, *args[1:], **kw)
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return self
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return generate
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# these can be replaced by sqlalchemy.ext.instrumentation
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# if augmented class instrumentation is enabled.
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def manager_of_class(cls):
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return cls.__dict__.get(DEFAULT_MANAGER_ATTR, None)
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instance_state = operator.attrgetter(DEFAULT_STATE_ATTR)
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instance_dict = operator.attrgetter('__dict__')
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def instance_str(instance):
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"""Return a string describing an instance."""
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return state_str(instance_state(instance))
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def state_str(state):
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"""Return a string describing an instance via its InstanceState."""
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if state is None:
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return "None"
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else:
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return '<%s at 0x%x>' % (state.class_.__name__, id(state.obj()))
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def state_class_str(state):
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"""Return a string describing an instance's class via its InstanceState."""
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if state is None:
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return "None"
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else:
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return '<%s>' % (state.class_.__name__, )
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def attribute_str(instance, attribute):
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return instance_str(instance) + "." + attribute
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def state_attribute_str(state, attribute):
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return state_str(state) + "." + attribute
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def object_mapper(instance):
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"""Given an object, return the primary Mapper associated with the object
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instance.
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Raises :class:`sqlalchemy.orm.exc.UnmappedInstanceError`
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if no mapping is configured.
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This function is available via the inspection system as::
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inspect(instance).mapper
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Using the inspection system will raise
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:class:`sqlalchemy.exc.NoInspectionAvailable` if the instance is
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not part of a mapping.
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"""
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return object_state(instance).mapper
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def object_state(instance):
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"""Given an object, return the :class:`.InstanceState`
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associated with the object.
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Raises :class:`sqlalchemy.orm.exc.UnmappedInstanceError`
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if no mapping is configured.
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Equivalent functionality is available via the :func:`.inspect`
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function as::
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inspect(instance)
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Using the inspection system will raise
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:class:`sqlalchemy.exc.NoInspectionAvailable` if the instance is
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not part of a mapping.
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"""
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state = _inspect_mapped_object(instance)
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if state is None:
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raise exc.UnmappedInstanceError(instance)
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else:
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return state
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@inspection._inspects(object)
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def _inspect_mapped_object(instance):
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try:
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return instance_state(instance)
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# TODO: whats the py-2/3 syntax to catch two
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# different kinds of exceptions at once ?
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except exc.UnmappedClassError:
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return None
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except exc.NO_STATE:
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return None
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def _class_to_mapper(class_or_mapper):
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insp = inspection.inspect(class_or_mapper, False)
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if insp is not None:
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return insp.mapper
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else:
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raise exc.UnmappedClassError(class_or_mapper)
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def _mapper_or_none(entity):
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"""Return the :class:`.Mapper` for the given class or None if the
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class is not mapped."""
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insp = inspection.inspect(entity, False)
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if insp is not None:
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return insp.mapper
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else:
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return None
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def _is_mapped_class(entity):
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"""Return True if the given object is a mapped class,
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:class:`.Mapper`, or :class:`.AliasedClass`."""
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insp = inspection.inspect(entity, False)
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return insp is not None and \
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hasattr(insp, "mapper") and \
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(
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insp.is_mapper
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or insp.is_aliased_class
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)
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def _attr_as_key(attr):
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if hasattr(attr, 'key'):
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return attr.key
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else:
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return expression._column_as_key(attr)
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def _orm_columns(entity):
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insp = inspection.inspect(entity, False)
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if hasattr(insp, 'selectable'):
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return [c for c in insp.selectable.c]
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else:
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return [entity]
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def _is_aliased_class(entity):
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insp = inspection.inspect(entity, False)
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return insp is not None and \
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getattr(insp, "is_aliased_class", False)
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def _entity_descriptor(entity, key):
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"""Return a class attribute given an entity and string name.
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May return :class:`.InstrumentedAttribute` or user-defined
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attribute.
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"""
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insp = inspection.inspect(entity)
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if insp.is_selectable:
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description = entity
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entity = insp.c
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elif insp.is_aliased_class:
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entity = insp.entity
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description = entity
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elif hasattr(insp, "mapper"):
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description = entity = insp.mapper.class_
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else:
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description = entity
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try:
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return getattr(entity, key)
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except AttributeError:
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raise sa_exc.InvalidRequestError(
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"Entity '%s' has no property '%s'" %
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(description, key)
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)
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_state_mapper = util.dottedgetter('manager.mapper')
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@inspection._inspects(type)
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def _inspect_mapped_class(class_, configure=False):
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try:
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class_manager = manager_of_class(class_)
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if not class_manager.is_mapped:
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return None
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mapper = class_manager.mapper
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if configure and mapper._new_mappers:
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mapper._configure_all()
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return mapper
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except exc.NO_STATE:
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return None
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def class_mapper(class_, configure=True):
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"""Given a class, return the primary :class:`.Mapper` associated
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with the key.
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Raises :exc:`.UnmappedClassError` if no mapping is configured
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on the given class, or :exc:`.ArgumentError` if a non-class
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object is passed.
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Equivalent functionality is available via the :func:`.inspect`
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function as::
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inspect(some_mapped_class)
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Using the inspection system will raise
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:class:`sqlalchemy.exc.NoInspectionAvailable` if the class is not mapped.
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"""
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mapper = _inspect_mapped_class(class_, configure=configure)
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if mapper is None:
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if not isinstance(class_, type):
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raise sa_exc.ArgumentError(
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"Class object expected, got '%r'." % (class_, ))
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raise exc.UnmappedClassError(class_)
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else:
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return mapper
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class _InspectionAttr(object):
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"""A base class applied to all ORM objects that can be returned
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by the :func:`.inspect` function.
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The attributes defined here allow the usage of simple boolean
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checks to test basic facts about the object returned.
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While the boolean checks here are basically the same as using
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the Python isinstance() function, the flags here can be used without
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the need to import all of these classes, and also such that
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the SQLAlchemy class system can change while leaving the flags
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here intact for forwards-compatibility.
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"""
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is_selectable = False
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"""Return True if this object is an instance of :class:`.Selectable`."""
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is_aliased_class = False
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"""True if this object is an instance of :class:`.AliasedClass`."""
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is_instance = False
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"""True if this object is an instance of :class:`.InstanceState`."""
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is_mapper = False
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"""True if this object is an instance of :class:`.Mapper`."""
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is_property = False
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"""True if this object is an instance of :class:`.MapperProperty`."""
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is_attribute = False
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"""True if this object is a Python :term:`descriptor`.
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This can refer to one of many types. Usually a
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:class:`.QueryableAttribute` which handles attributes events on behalf
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of a :class:`.MapperProperty`. But can also be an extension type
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such as :class:`.AssociationProxy` or :class:`.hybrid_property`.
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The :attr:`._InspectionAttr.extension_type` will refer to a constant
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identifying the specific subtype.
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.. seealso::
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:attr:`.Mapper.all_orm_descriptors`
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"""
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is_clause_element = False
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"""True if this object is an instance of :class:`.ClauseElement`."""
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extension_type = NOT_EXTENSION
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"""The extension type, if any.
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Defaults to :data:`.interfaces.NOT_EXTENSION`
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.. versionadded:: 0.8.0
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.. seealso::
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:data:`.HYBRID_METHOD`
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:data:`.HYBRID_PROPERTY`
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:data:`.ASSOCIATION_PROXY`
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"""
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class _MappedAttribute(object):
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"""Mixin for attributes which should be replaced by mapper-assigned
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attributes.
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"""
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