949 lines
32 KiB
Python
949 lines
32 KiB
Python
# orm/strategy_options.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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"""
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"""
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from .interfaces import MapperOption, PropComparator
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from .. import util
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from ..sql.base import _generative, Generative
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from .. import exc as sa_exc, inspect
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from .base import _is_aliased_class, _class_to_mapper
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from . import util as orm_util
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from .path_registry import PathRegistry, TokenRegistry, \
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_WILDCARD_TOKEN, _DEFAULT_TOKEN
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class Load(Generative, MapperOption):
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"""Represents loader options which modify the state of a
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:class:`.Query` in order to affect how various mapped attributes are loaded.
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.. versionadded:: 0.9.0 The :meth:`.Load` system is a new foundation for
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the existing system of loader options, including options such as
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:func:`.orm.joinedload`, :func:`.orm.defer`, and others. In particular,
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it introduces a new method-chained system that replaces the need for
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dot-separated paths as well as "_all()" options such as :func:`.orm.joinedload_all`.
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A :class:`.Load` object can be used directly or indirectly. To use one
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directly, instantiate given the parent class. This style of usage is
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useful when dealing with a :class:`.Query` that has multiple entities,
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or when producing a loader option that can be applied generically to
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any style of query::
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myopt = Load(MyClass).joinedload("widgets")
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The above ``myopt`` can now be used with :meth:`.Query.options`::
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session.query(MyClass).options(myopt)
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The :class:`.Load` construct is invoked indirectly whenever one makes use
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of the various loader options that are present in ``sqlalchemy.orm``, including
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options such as :func:`.orm.joinedload`, :func:`.orm.defer`, :func:`.orm.subqueryload`,
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and all the rest. These constructs produce an "anonymous" form of the
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:class:`.Load` object which tracks attributes and options, but is not linked
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to a parent class until it is associated with a parent :class:`.Query`::
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# produce "unbound" Load object
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myopt = joinedload("widgets")
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# when applied using options(), the option is "bound" to the
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# class observed in the given query, e.g. MyClass
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session.query(MyClass).options(myopt)
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Whether the direct or indirect style is used, the :class:`.Load` object
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returned now represents a specific "path" along the entities of a :class:`.Query`.
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This path can be traversed using a standard method-chaining approach.
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Supposing a class hierarchy such as ``User``, ``User.addresses -> Address``,
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``User.orders -> Order`` and ``Order.items -> Item``, we can specify a variety
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of loader options along each element in the "path"::
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session.query(User).options(
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joinedload("addresses"),
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subqueryload("orders").joinedload("items")
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)
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Where above, the ``addresses`` collection will be joined-loaded, the
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``orders`` collection will be subquery-loaded, and within that subquery load
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the ``items`` collection will be joined-loaded.
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"""
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def __init__(self, entity):
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insp = inspect(entity)
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self.path = insp._path_registry
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self.context = {}
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self.local_opts = {}
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def _generate(self):
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cloned = super(Load, self)._generate()
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cloned.local_opts = {}
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return cloned
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strategy = None
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propagate_to_loaders = False
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def process_query(self, query):
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self._process(query, True)
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def process_query_conditionally(self, query):
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self._process(query, False)
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def _process(self, query, raiseerr):
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current_path = query._current_path
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if current_path:
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for (token, start_path), loader in self.context.items():
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chopped_start_path = self._chop_path(start_path, current_path)
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if chopped_start_path is not None:
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query._attributes[(token, chopped_start_path)] = loader
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else:
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query._attributes.update(self.context)
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def _generate_path(self, path, attr, wildcard_key, raiseerr=True):
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if raiseerr and not path.has_entity:
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if isinstance(path, TokenRegistry):
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raise sa_exc.ArgumentError(
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"Wildcard token cannot be followed by another entity")
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else:
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raise sa_exc.ArgumentError(
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"Attribute '%s' of entity '%s' does not "
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"refer to a mapped entity" %
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(path.prop.key, path.parent.entity)
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)
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if isinstance(attr, util.string_types):
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default_token = attr.endswith(_DEFAULT_TOKEN)
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if attr.endswith(_WILDCARD_TOKEN) or default_token:
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if default_token:
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self.propagate_to_loaders = False
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if wildcard_key:
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attr = "%s:%s" % (wildcard_key, attr)
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return path.token(attr)
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try:
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# use getattr on the class to work around
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# synonyms, hybrids, etc.
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attr = getattr(path.entity.class_, attr)
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except AttributeError:
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if raiseerr:
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raise sa_exc.ArgumentError(
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"Can't find property named '%s' on the "
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"mapped entity %s in this Query. " % (
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attr, path.entity)
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)
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else:
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return None
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else:
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attr = attr.property
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path = path[attr]
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else:
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prop = attr.property
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if not prop.parent.common_parent(path.mapper):
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if raiseerr:
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raise sa_exc.ArgumentError("Attribute '%s' does not "
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"link from element '%s'" % (attr, path.entity))
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else:
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return None
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if getattr(attr, '_of_type', None):
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ac = attr._of_type
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ext_info = inspect(ac)
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path_element = ext_info.mapper
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if not ext_info.is_aliased_class:
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ac = orm_util.with_polymorphic(
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ext_info.mapper.base_mapper,
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ext_info.mapper, aliased=True,
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_use_mapper_path=True)
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path.entity_path[prop].set(self.context,
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"path_with_polymorphic", inspect(ac))
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path = path[prop][path_element]
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else:
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path = path[prop]
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if path.has_entity:
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path = path.entity_path
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return path
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def _coerce_strat(self, strategy):
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if strategy is not None:
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strategy = tuple(sorted(strategy.items()))
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return strategy
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@_generative
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def set_relationship_strategy(self, attr, strategy, propagate_to_loaders=True):
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strategy = self._coerce_strat(strategy)
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self.propagate_to_loaders = propagate_to_loaders
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# if the path is a wildcard, this will set propagate_to_loaders=False
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self.path = self._generate_path(self.path, attr, "relationship")
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self.strategy = strategy
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if strategy is not None:
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self._set_path_strategy()
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@_generative
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def set_column_strategy(self, attrs, strategy, opts=None):
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strategy = self._coerce_strat(strategy)
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for attr in attrs:
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path = self._generate_path(self.path, attr, "column")
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cloned = self._generate()
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cloned.strategy = strategy
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cloned.path = path
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cloned.propagate_to_loaders = True
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if opts:
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cloned.local_opts.update(opts)
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cloned._set_path_strategy()
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def _set_path_strategy(self):
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if self.path.has_entity:
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self.path.parent.set(self.context, "loader", self)
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else:
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self.path.set(self.context, "loader", self)
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def __getstate__(self):
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d = self.__dict__.copy()
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d["path"] = self.path.serialize()
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return d
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def __setstate__(self, state):
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self.__dict__.update(state)
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self.path = PathRegistry.deserialize(self.path)
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def _chop_path(self, to_chop, path):
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i = -1
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for i, (c_token, p_token) in enumerate(zip(to_chop, path.path)):
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if isinstance(c_token, util.string_types):
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# TODO: this is approximated from the _UnboundLoad
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# version and probably has issues, not fully covered.
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if i == 0 and c_token.endswith(':' + _DEFAULT_TOKEN):
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return to_chop
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elif c_token != 'relationship:%s' % (_WILDCARD_TOKEN,) and c_token != p_token.key:
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return None
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if c_token is p_token:
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continue
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else:
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return None
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return to_chop[i+1:]
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class _UnboundLoad(Load):
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"""Represent a loader option that isn't tied to a root entity.
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The loader option will produce an entity-linked :class:`.Load`
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object when it is passed :meth:`.Query.options`.
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This provides compatibility with the traditional system
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of freestanding options, e.g. ``joinedload('x.y.z')``.
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"""
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def __init__(self):
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self.path = ()
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self._to_bind = set()
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self.local_opts = {}
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_is_chain_link = False
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def _set_path_strategy(self):
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self._to_bind.add(self)
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def _generate_path(self, path, attr, wildcard_key):
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if wildcard_key and isinstance(attr, util.string_types) and \
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attr in (_WILDCARD_TOKEN, _DEFAULT_TOKEN):
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if attr == _DEFAULT_TOKEN:
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self.propagate_to_loaders = False
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attr = "%s:%s" % (wildcard_key, attr)
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return path + (attr, )
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def __getstate__(self):
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d = self.__dict__.copy()
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d['path'] = ret = []
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for token in util.to_list(self.path):
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if isinstance(token, PropComparator):
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ret.append((token._parentmapper.class_, token.key))
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else:
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ret.append(token)
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return d
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def __setstate__(self, state):
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ret = []
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for key in state['path']:
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if isinstance(key, tuple):
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cls, propkey = key
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ret.append(getattr(cls, propkey))
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else:
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ret.append(key)
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state['path'] = tuple(ret)
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self.__dict__ = state
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def _process(self, query, raiseerr):
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for val in self._to_bind:
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val._bind_loader(query, query._attributes, raiseerr)
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@classmethod
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def _from_keys(self, meth, keys, chained, kw):
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opt = _UnboundLoad()
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def _split_key(key):
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if isinstance(key, util.string_types):
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# coerce fooload('*') into "default loader strategy"
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if key == _WILDCARD_TOKEN:
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return (_DEFAULT_TOKEN, )
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# coerce fooload(".*") into "wildcard on default entity"
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elif key.startswith("." + _WILDCARD_TOKEN):
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key = key[1:]
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return key.split(".")
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else:
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return (key,)
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all_tokens = [token for key in keys for token in _split_key(key)]
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for token in all_tokens[0:-1]:
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if chained:
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opt = meth(opt, token, **kw)
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else:
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opt = opt.defaultload(token)
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opt._is_chain_link = True
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opt = meth(opt, all_tokens[-1], **kw)
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opt._is_chain_link = False
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return opt
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def _chop_path(self, to_chop, path):
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i = -1
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for i, (c_token, (p_mapper, p_prop)) in enumerate(zip(to_chop, path.pairs())):
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if isinstance(c_token, util.string_types):
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if i == 0 and c_token.endswith(':' + _DEFAULT_TOKEN):
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return to_chop
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elif c_token != 'relationship:%s' % (_WILDCARD_TOKEN,) and c_token != p_prop.key:
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return None
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elif isinstance(c_token, PropComparator):
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if c_token.property is not p_prop:
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return None
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else:
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i += 1
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return to_chop[i:]
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def _bind_loader(self, query, context, raiseerr):
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start_path = self.path
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# _current_path implies we're in a
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# secondary load with an existing path
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current_path = query._current_path
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if current_path:
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start_path = self._chop_path(start_path, current_path)
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if not start_path:
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return None
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token = start_path[0]
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if isinstance(token, util.string_types):
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entity = self._find_entity_basestring(query, token, raiseerr)
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elif isinstance(token, PropComparator):
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prop = token.property
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entity = self._find_entity_prop_comparator(
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query,
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prop.key,
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token._parententity,
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raiseerr)
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else:
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raise sa_exc.ArgumentError(
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"mapper option expects "
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"string key or list of attributes")
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if not entity:
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return
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path_element = entity.entity_zero
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# transfer our entity-less state into a Load() object
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# with a real entity path.
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loader = Load(path_element)
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loader.context = context
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loader.strategy = self.strategy
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path = loader.path
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for token in start_path:
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loader.path = path = loader._generate_path(
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loader.path, token, None, raiseerr)
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if path is None:
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return
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loader.local_opts.update(self.local_opts)
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if loader.path.has_entity:
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effective_path = loader.path.parent
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else:
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effective_path = loader.path
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# prioritize "first class" options over those
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# that were "links in the chain", e.g. "x" and "y" in someload("x.y.z")
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# versus someload("x") / someload("x.y")
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if self._is_chain_link:
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effective_path.setdefault(context, "loader", loader)
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else:
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effective_path.set(context, "loader", loader)
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def _find_entity_prop_comparator(self, query, token, mapper, raiseerr):
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if _is_aliased_class(mapper):
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searchfor = mapper
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else:
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searchfor = _class_to_mapper(mapper)
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for ent in query._mapper_entities:
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if ent.corresponds_to(searchfor):
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return ent
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else:
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if raiseerr:
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if not list(query._mapper_entities):
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raise sa_exc.ArgumentError(
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"Query has only expression-based entities - "
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"can't find property named '%s'."
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% (token, )
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)
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else:
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raise sa_exc.ArgumentError(
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"Can't find property '%s' on any entity "
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"specified in this Query. Note the full path "
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"from root (%s) to target entity must be specified."
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% (token, ",".join(str(x) for
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x in query._mapper_entities))
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)
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else:
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return None
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def _find_entity_basestring(self, query, token, raiseerr):
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if token.endswith(':' + _WILDCARD_TOKEN):
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if len(list(query._mapper_entities)) != 1:
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if raiseerr:
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raise sa_exc.ArgumentError(
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"Wildcard loader can only be used with exactly "
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"one entity. Use Load(ent) to specify "
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"specific entities.")
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elif token.endswith(_DEFAULT_TOKEN):
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raiseerr = False
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for ent in query._mapper_entities:
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# return only the first _MapperEntity when searching
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# based on string prop name. Ideally object
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# attributes are used to specify more exactly.
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return ent
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else:
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if raiseerr:
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raise sa_exc.ArgumentError(
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"Query has only expression-based entities - "
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"can't find property named '%s'."
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% (token, )
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)
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else:
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return None
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class loader_option(object):
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def __init__(self):
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pass
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def __call__(self, fn):
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self.name = name = fn.__name__
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self.fn = fn
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if hasattr(Load, name):
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raise TypeError("Load class already has a %s method." % (name))
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setattr(Load, name, fn)
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return self
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def _add_unbound_fn(self, fn):
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self._unbound_fn = fn
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fn_doc = self.fn.__doc__
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self.fn.__doc__ = """Produce a new :class:`.Load` object with the
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:func:`.orm.%(name)s` option applied.
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See :func:`.orm.%(name)s` for usage examples.
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""" % {"name": self.name}
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fn.__doc__ = fn_doc
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return self
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def _add_unbound_all_fn(self, fn):
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self._unbound_all_fn = fn
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fn.__doc__ = """Produce a standalone "all" option for :func:`.orm.%(name)s`.
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.. deprecated:: 0.9.0
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The "_all()" style is replaced by method chaining, e.g.::
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session.query(MyClass).options(
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%(name)s("someattribute").%(name)s("anotherattribute")
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)
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""" % {"name": self.name}
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return self
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@loader_option()
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def contains_eager(loadopt, attr, alias=None):
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"""Indicate that the given attribute should be eagerly loaded from
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columns stated manually in the query.
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This function is part of the :class:`.Load` interface and supports
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both method-chained and standalone operation.
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The option is used in conjunction with an explicit join that loads
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the desired rows, i.e.::
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sess.query(Order).\\
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join(Order.user).\\
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options(contains_eager(Order.user))
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The above query would join from the ``Order`` entity to its related
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``User`` entity, and the returned ``Order`` objects would have the
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``Order.user`` attribute pre-populated.
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:func:`contains_eager` also accepts an `alias` argument, which is the
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string name of an alias, an :func:`~sqlalchemy.sql.expression.alias`
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construct, or an :func:`~sqlalchemy.orm.aliased` construct. Use this when
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the eagerly-loaded rows are to come from an aliased table::
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|
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user_alias = aliased(User)
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sess.query(Order).\\
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join((user_alias, Order.user)).\\
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|
options(contains_eager(Order.user, alias=user_alias))
|
|
|
|
.. seealso::
|
|
|
|
:ref:`contains_eager`
|
|
|
|
"""
|
|
if alias is not None:
|
|
if not isinstance(alias, str):
|
|
info = inspect(alias)
|
|
alias = info.selectable
|
|
|
|
cloned = loadopt.set_relationship_strategy(
|
|
attr,
|
|
{"lazy": "joined"},
|
|
propagate_to_loaders=False
|
|
)
|
|
cloned.local_opts['eager_from_alias'] = alias
|
|
return cloned
|
|
|
|
@contains_eager._add_unbound_fn
|
|
def contains_eager(*keys, **kw):
|
|
return _UnboundLoad()._from_keys(_UnboundLoad.contains_eager, keys, True, kw)
|
|
|
|
@loader_option()
|
|
def load_only(loadopt, *attrs):
|
|
"""Indicate that for a particular entity, only the given list
|
|
of column-based attribute names should be loaded; all others will be
|
|
deferred.
|
|
|
|
This function is part of the :class:`.Load` interface and supports
|
|
both method-chained and standalone operation.
|
|
|
|
Example - given a class ``User``, load only the ``name`` and ``fullname``
|
|
attributes::
|
|
|
|
session.query(User).options(load_only("name", "fullname"))
|
|
|
|
Example - given a relationship ``User.addresses -> Address``, specify
|
|
subquery loading for the ``User.addresses`` collection, but on each ``Address``
|
|
object load only the ``email_address`` attribute::
|
|
|
|
session.query(User).options(
|
|
subqueryload("addreses").load_only("email_address")
|
|
)
|
|
|
|
For a :class:`.Query` that has multiple entities, the lead entity can be
|
|
specifically referred to using the :class:`.Load` constructor::
|
|
|
|
session.query(User, Address).join(User.addresses).options(
|
|
Load(User).load_only("name", "fullname"),
|
|
Load(Address).load_only("email_addres")
|
|
)
|
|
|
|
|
|
.. versionadded:: 0.9.0
|
|
|
|
"""
|
|
cloned = loadopt.set_column_strategy(
|
|
attrs,
|
|
{"deferred": False, "instrument": True}
|
|
)
|
|
cloned.set_column_strategy("*",
|
|
{"deferred": True, "instrument": True})
|
|
return cloned
|
|
|
|
@load_only._add_unbound_fn
|
|
def load_only(*attrs):
|
|
return _UnboundLoad().load_only(*attrs)
|
|
|
|
@loader_option()
|
|
def joinedload(loadopt, attr, innerjoin=None):
|
|
"""Indicate that the given attribute should be loaded using joined
|
|
eager loading.
|
|
|
|
This function is part of the :class:`.Load` interface and supports
|
|
both method-chained and standalone operation.
|
|
|
|
examples::
|
|
|
|
# joined-load the "orders" collection on "User"
|
|
query(User).options(joinedload(User.orders))
|
|
|
|
# joined-load Order.items and then Item.keywords
|
|
query(Order).options(joinedload(Order.items).joinedload(Item.keywords))
|
|
|
|
# lazily load Order.items, but when Items are loaded,
|
|
# joined-load the keywords collection
|
|
query(Order).options(lazyload(Order.items).joinedload(Item.keywords))
|
|
|
|
:param innerjoin: if ``True``, indicates that the joined eager load should
|
|
use an inner join instead of the default of left outer join::
|
|
|
|
query(Order).options(joinedload(Order.user, innerjoin=True))
|
|
|
|
If the joined-eager load is chained onto an existing LEFT OUTER JOIN,
|
|
``innerjoin=True`` will be bypassed and the join will continue to
|
|
chain as LEFT OUTER JOIN so that the results don't change. As an alternative,
|
|
specify the value ``"nested"``. This will instead nest the join
|
|
on the right side, e.g. using the form "a LEFT OUTER JOIN (b JOIN c)".
|
|
|
|
.. versionadded:: 0.9.4 Added ``innerjoin="nested"`` option to support
|
|
nesting of eager "inner" joins.
|
|
|
|
.. note::
|
|
|
|
The joins produced by :func:`.orm.joinedload` are **anonymously aliased**.
|
|
The criteria by which the join proceeds cannot be modified, nor can the
|
|
:class:`.Query` refer to these joins in any way, including ordering.
|
|
|
|
To produce a specific SQL JOIN which is explicitly available, use
|
|
:meth:`.Query.join`. To combine explicit JOINs with eager loading
|
|
of collections, use :func:`.orm.contains_eager`; see :ref:`contains_eager`.
|
|
|
|
.. seealso::
|
|
|
|
:ref:`loading_toplevel`
|
|
|
|
:ref:`contains_eager`
|
|
|
|
:func:`.orm.subqueryload`
|
|
|
|
:func:`.orm.lazyload`
|
|
|
|
:paramref:`.relationship.lazy`
|
|
|
|
:paramref:`.relationship.innerjoin` - :func:`.relationship`-level version
|
|
of the :paramref:`.joinedload.innerjoin` option.
|
|
|
|
"""
|
|
loader = loadopt.set_relationship_strategy(attr, {"lazy": "joined"})
|
|
if innerjoin is not None:
|
|
loader.local_opts['innerjoin'] = innerjoin
|
|
return loader
|
|
|
|
@joinedload._add_unbound_fn
|
|
def joinedload(*keys, **kw):
|
|
return _UnboundLoad._from_keys(
|
|
_UnboundLoad.joinedload, keys, False, kw)
|
|
|
|
@joinedload._add_unbound_all_fn
|
|
def joinedload_all(*keys, **kw):
|
|
return _UnboundLoad._from_keys(
|
|
_UnboundLoad.joinedload, keys, True, kw)
|
|
|
|
|
|
@loader_option()
|
|
def subqueryload(loadopt, attr):
|
|
"""Indicate that the given attribute should be loaded using
|
|
subquery eager loading.
|
|
|
|
This function is part of the :class:`.Load` interface and supports
|
|
both method-chained and standalone operation.
|
|
|
|
examples::
|
|
|
|
# subquery-load the "orders" collection on "User"
|
|
query(User).options(subqueryload(User.orders))
|
|
|
|
# subquery-load Order.items and then Item.keywords
|
|
query(Order).options(subqueryload(Order.items).subqueryload(Item.keywords))
|
|
|
|
# lazily load Order.items, but when Items are loaded,
|
|
# subquery-load the keywords collection
|
|
query(Order).options(lazyload(Order.items).subqueryload(Item.keywords))
|
|
|
|
|
|
.. seealso::
|
|
|
|
:ref:`loading_toplevel`
|
|
|
|
:func:`.orm.joinedload`
|
|
|
|
:func:`.orm.lazyload`
|
|
|
|
:paramref:`.relationship.lazy`
|
|
|
|
"""
|
|
return loadopt.set_relationship_strategy(attr, {"lazy": "subquery"})
|
|
|
|
@subqueryload._add_unbound_fn
|
|
def subqueryload(*keys):
|
|
return _UnboundLoad._from_keys(_UnboundLoad.subqueryload, keys, False, {})
|
|
|
|
@subqueryload._add_unbound_all_fn
|
|
def subqueryload_all(*keys):
|
|
return _UnboundLoad._from_keys(_UnboundLoad.subqueryload, keys, True, {})
|
|
|
|
@loader_option()
|
|
def lazyload(loadopt, attr):
|
|
"""Indicate that the given attribute should be loaded using "lazy"
|
|
loading.
|
|
|
|
This function is part of the :class:`.Load` interface and supports
|
|
both method-chained and standalone operation.
|
|
|
|
.. seealso::
|
|
|
|
:paramref:`.relationship.lazy`
|
|
|
|
"""
|
|
return loadopt.set_relationship_strategy(attr, {"lazy": "select"})
|
|
|
|
@lazyload._add_unbound_fn
|
|
def lazyload(*keys):
|
|
return _UnboundLoad._from_keys(_UnboundLoad.lazyload, keys, False, {})
|
|
|
|
@lazyload._add_unbound_all_fn
|
|
def lazyload_all(*keys):
|
|
return _UnboundLoad._from_keys(_UnboundLoad.lazyload, keys, True, {})
|
|
|
|
@loader_option()
|
|
def immediateload(loadopt, attr):
|
|
"""Indicate that the given attribute should be loaded using
|
|
an immediate load with a per-attribute SELECT statement.
|
|
|
|
This function is part of the :class:`.Load` interface and supports
|
|
both method-chained and standalone operation.
|
|
|
|
.. seealso::
|
|
|
|
:ref:`loading_toplevel`
|
|
|
|
:func:`.orm.joinedload`
|
|
|
|
:func:`.orm.lazyload`
|
|
|
|
:paramref:`.relationship.lazy`
|
|
|
|
"""
|
|
loader = loadopt.set_relationship_strategy(attr, {"lazy": "immediate"})
|
|
return loader
|
|
|
|
@immediateload._add_unbound_fn
|
|
def immediateload(*keys):
|
|
return _UnboundLoad._from_keys(_UnboundLoad.immediateload, keys, False, {})
|
|
|
|
|
|
@loader_option()
|
|
def noload(loadopt, attr):
|
|
"""Indicate that the given relationship attribute should remain unloaded.
|
|
|
|
This function is part of the :class:`.Load` interface and supports
|
|
both method-chained and standalone operation.
|
|
|
|
:func:`.orm.noload` applies to :func:`.relationship` attributes; for
|
|
column-based attributes, see :func:`.orm.defer`.
|
|
|
|
"""
|
|
|
|
return loadopt.set_relationship_strategy(attr, {"lazy": "noload"})
|
|
|
|
@noload._add_unbound_fn
|
|
def noload(*keys):
|
|
return _UnboundLoad._from_keys(_UnboundLoad.noload, keys, False, {})
|
|
|
|
@loader_option()
|
|
def defaultload(loadopt, attr):
|
|
"""Indicate an attribute should load using its default loader style.
|
|
|
|
This method is used to link to other loader options, such as
|
|
to set the :func:`.orm.defer` option on a class that is linked to
|
|
a relationship of the parent class being loaded, :func:`.orm.defaultload`
|
|
can be used to navigate this path without changing the loading style
|
|
of the relationship::
|
|
|
|
session.query(MyClass).options(defaultload("someattr").defer("some_column"))
|
|
|
|
.. seealso::
|
|
|
|
:func:`.orm.defer`
|
|
|
|
:func:`.orm.undefer`
|
|
|
|
"""
|
|
return loadopt.set_relationship_strategy(
|
|
attr,
|
|
None
|
|
)
|
|
|
|
@defaultload._add_unbound_fn
|
|
def defaultload(*keys):
|
|
return _UnboundLoad._from_keys(_UnboundLoad.defaultload, keys, False, {})
|
|
|
|
@loader_option()
|
|
def defer(loadopt, key):
|
|
"""Indicate that the given column-oriented attribute should be deferred, e.g.
|
|
not loaded until accessed.
|
|
|
|
This function is part of the :class:`.Load` interface and supports
|
|
both method-chained and standalone operation.
|
|
|
|
e.g.::
|
|
|
|
from sqlalchemy.orm import defer
|
|
|
|
session.query(MyClass).options(
|
|
defer("attribute_one"),
|
|
defer("attribute_two"))
|
|
|
|
session.query(MyClass).options(
|
|
defer(MyClass.attribute_one),
|
|
defer(MyClass.attribute_two))
|
|
|
|
To specify a deferred load of an attribute on a related class,
|
|
the path can be specified one token at a time, specifying the loading
|
|
style for each link along the chain. To leave the loading style
|
|
for a link unchanged, use :func:`.orm.defaultload`::
|
|
|
|
session.query(MyClass).options(defaultload("someattr").defer("some_column"))
|
|
|
|
A :class:`.Load` object that is present on a certain path can have
|
|
:meth:`.Load.defer` called multiple times, each will operate on the same
|
|
parent entity::
|
|
|
|
|
|
session.query(MyClass).options(
|
|
defaultload("someattr").
|
|
defer("some_column").
|
|
defer("some_other_column").
|
|
defer("another_column")
|
|
)
|
|
|
|
:param key: Attribute to be deferred.
|
|
|
|
:param \*addl_attrs: Deprecated; this option supports the old 0.8 style
|
|
of specifying a path as a series of attributes, which is now superseded
|
|
by the method-chained style.
|
|
|
|
.. seealso::
|
|
|
|
:ref:`deferred`
|
|
|
|
:func:`.orm.undefer`
|
|
|
|
"""
|
|
return loadopt.set_column_strategy(
|
|
(key, ),
|
|
{"deferred": True, "instrument": True}
|
|
)
|
|
|
|
|
|
@defer._add_unbound_fn
|
|
def defer(key, *addl_attrs):
|
|
return _UnboundLoad._from_keys(_UnboundLoad.defer, (key, ) + addl_attrs, False, {})
|
|
|
|
@loader_option()
|
|
def undefer(loadopt, key):
|
|
"""Indicate that the given column-oriented attribute should be undeferred, e.g.
|
|
specified within the SELECT statement of the entity as a whole.
|
|
|
|
The column being undeferred is typically set up on the mapping as a
|
|
:func:`.deferred` attribute.
|
|
|
|
This function is part of the :class:`.Load` interface and supports
|
|
both method-chained and standalone operation.
|
|
|
|
Examples::
|
|
|
|
# undefer two columns
|
|
session.query(MyClass).options(undefer("col1"), undefer("col2"))
|
|
|
|
# undefer all columns specific to a single class using Load + *
|
|
session.query(MyClass, MyOtherClass).options(Load(MyClass).undefer("*"))
|
|
|
|
:param key: Attribute to be undeferred.
|
|
|
|
:param \*addl_attrs: Deprecated; this option supports the old 0.8 style
|
|
of specifying a path as a series of attributes, which is now superseded
|
|
by the method-chained style.
|
|
|
|
.. seealso::
|
|
|
|
:ref:`deferred`
|
|
|
|
:func:`.orm.defer`
|
|
|
|
:func:`.orm.undefer_group`
|
|
|
|
"""
|
|
return loadopt.set_column_strategy(
|
|
(key, ),
|
|
{"deferred": False, "instrument": True}
|
|
)
|
|
|
|
@undefer._add_unbound_fn
|
|
def undefer(key, *addl_attrs):
|
|
return _UnboundLoad._from_keys(_UnboundLoad.undefer, (key, ) + addl_attrs, False, {})
|
|
|
|
@loader_option()
|
|
def undefer_group(loadopt, name):
|
|
"""Indicate that columns within the given deferred group name should be undeferred.
|
|
|
|
The columns being undeferred are set up on the mapping as
|
|
:func:`.deferred` attributes and include a "group" name.
|
|
|
|
E.g::
|
|
|
|
session.query(MyClass).options(undefer_group("large_attrs"))
|
|
|
|
To undefer a group of attributes on a related entity, the path can be
|
|
spelled out using relationship loader options, such as :func:`.orm.defaultload`::
|
|
|
|
session.query(MyClass).options(defaultload("someattr").undefer_group("large_attrs"))
|
|
|
|
.. versionchanged:: 0.9.0 :func:`.orm.undefer_group` is now specific to a
|
|
particiular entity load path.
|
|
|
|
.. seealso::
|
|
|
|
:ref:`deferred`
|
|
|
|
:func:`.orm.defer`
|
|
|
|
:func:`.orm.undefer`
|
|
|
|
"""
|
|
return loadopt.set_column_strategy(
|
|
"*",
|
|
None,
|
|
{"undefer_group": name}
|
|
)
|
|
|
|
@undefer_group._add_unbound_fn
|
|
def undefer_group(name):
|
|
return _UnboundLoad().undefer_group(name)
|
|
|