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2157 lines
74 KiB
Python
2157 lines
74 KiB
Python
# orm/util.py
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# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors
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# <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: https://www.opensource.org/licenses/mit-license.php
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import re
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import types
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import weakref
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from . import attributes # noqa
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from .base import _class_to_mapper # noqa
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from .base import _never_set # noqa
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from .base import _none_set # noqa
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from .base import attribute_str # noqa
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from .base import class_mapper # noqa
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from .base import InspectionAttr # noqa
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from .base import instance_str # noqa
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from .base import object_mapper # noqa
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from .base import object_state # noqa
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from .base import state_attribute_str # noqa
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from .base import state_class_str # noqa
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from .base import state_str # noqa
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from .interfaces import CriteriaOption
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from .interfaces import MapperProperty # noqa
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from .interfaces import ORMColumnsClauseRole
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from .interfaces import ORMEntityColumnsClauseRole
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from .interfaces import ORMFromClauseRole
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from .interfaces import PropComparator # noqa
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from .path_registry import PathRegistry # noqa
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from .. import event
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from .. import exc as sa_exc
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from .. import inspection
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from .. import sql
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from .. import util
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from ..engine.result import result_tuple
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from ..sql import base as sql_base
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from ..sql import coercions
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from ..sql import expression
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from ..sql import lambdas
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from ..sql import roles
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from ..sql import util as sql_util
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from ..sql import visitors
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from ..sql.annotation import SupportsCloneAnnotations
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from ..sql.base import ColumnCollection
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all_cascades = frozenset(
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(
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"delete",
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"delete-orphan",
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"all",
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"merge",
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"expunge",
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"save-update",
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"refresh-expire",
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"none",
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)
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)
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class CascadeOptions(frozenset):
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"""Keeps track of the options sent to
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:paramref:`.relationship.cascade`"""
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_add_w_all_cascades = all_cascades.difference(
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["all", "none", "delete-orphan"]
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)
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_allowed_cascades = all_cascades
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_viewonly_cascades = ["expunge", "all", "none", "refresh-expire"]
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__slots__ = (
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"save_update",
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"delete",
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"refresh_expire",
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"merge",
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"expunge",
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"delete_orphan",
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)
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def __new__(cls, value_list):
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if isinstance(value_list, util.string_types) or value_list is None:
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return cls.from_string(value_list)
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values = set(value_list)
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if values.difference(cls._allowed_cascades):
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raise sa_exc.ArgumentError(
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"Invalid cascade option(s): %s"
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% ", ".join(
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[
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repr(x)
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for x in sorted(
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values.difference(cls._allowed_cascades)
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)
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]
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)
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)
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if "all" in values:
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values.update(cls._add_w_all_cascades)
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if "none" in values:
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values.clear()
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values.discard("all")
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self = frozenset.__new__(CascadeOptions, values)
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self.save_update = "save-update" in values
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self.delete = "delete" in values
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self.refresh_expire = "refresh-expire" in values
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self.merge = "merge" in values
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self.expunge = "expunge" in values
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self.delete_orphan = "delete-orphan" in values
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if self.delete_orphan and not self.delete:
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util.warn(
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"The 'delete-orphan' cascade " "option requires 'delete'."
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)
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return self
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def __repr__(self):
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return "CascadeOptions(%r)" % (",".join([x for x in sorted(self)]))
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@classmethod
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def from_string(cls, arg):
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values = [c for c in re.split(r"\s*,\s*", arg or "") if c]
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return cls(values)
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def _validator_events(desc, key, validator, include_removes, include_backrefs):
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"""Runs a validation method on an attribute value to be set or
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appended.
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"""
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if not include_backrefs:
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def detect_is_backref(state, initiator):
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impl = state.manager[key].impl
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return initiator.impl is not impl
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if include_removes:
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def append(state, value, initiator):
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if initiator.op is not attributes.OP_BULK_REPLACE and (
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include_backrefs or not detect_is_backref(state, initiator)
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):
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return validator(state.obj(), key, value, False)
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else:
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return value
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def bulk_set(state, values, initiator):
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if include_backrefs or not detect_is_backref(state, initiator):
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obj = state.obj()
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values[:] = [
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validator(obj, key, value, False) for value in values
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]
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def set_(state, value, oldvalue, initiator):
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if include_backrefs or not detect_is_backref(state, initiator):
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return validator(state.obj(), key, value, False)
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else:
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return value
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def remove(state, value, initiator):
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if include_backrefs or not detect_is_backref(state, initiator):
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validator(state.obj(), key, value, True)
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else:
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def append(state, value, initiator):
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if initiator.op is not attributes.OP_BULK_REPLACE and (
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include_backrefs or not detect_is_backref(state, initiator)
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):
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return validator(state.obj(), key, value)
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else:
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return value
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def bulk_set(state, values, initiator):
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if include_backrefs or not detect_is_backref(state, initiator):
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obj = state.obj()
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values[:] = [validator(obj, key, value) for value in values]
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def set_(state, value, oldvalue, initiator):
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if include_backrefs or not detect_is_backref(state, initiator):
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return validator(state.obj(), key, value)
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else:
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return value
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event.listen(desc, "append", append, raw=True, retval=True)
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event.listen(desc, "bulk_replace", bulk_set, raw=True)
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event.listen(desc, "set", set_, raw=True, retval=True)
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if include_removes:
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event.listen(desc, "remove", remove, raw=True, retval=True)
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def polymorphic_union(
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table_map, typecolname, aliasname="p_union", cast_nulls=True
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):
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"""Create a ``UNION`` statement used by a polymorphic mapper.
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See :ref:`concrete_inheritance` for an example of how
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this is used.
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:param table_map: mapping of polymorphic identities to
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:class:`_schema.Table` objects.
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:param typecolname: string name of a "discriminator" column, which will be
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derived from the query, producing the polymorphic identity for
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each row. If ``None``, no polymorphic discriminator is generated.
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:param aliasname: name of the :func:`~sqlalchemy.sql.expression.alias()`
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construct generated.
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:param cast_nulls: if True, non-existent columns, which are represented
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as labeled NULLs, will be passed into CAST. This is a legacy behavior
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that is problematic on some backends such as Oracle - in which case it
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can be set to False.
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"""
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colnames = util.OrderedSet()
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colnamemaps = {}
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types = {}
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for key in table_map:
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table = table_map[key]
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table = coercions.expect(
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roles.StrictFromClauseRole, table, allow_select=True
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)
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table_map[key] = table
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m = {}
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for c in table.c:
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if c.key == typecolname:
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raise sa_exc.InvalidRequestError(
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"Polymorphic union can't use '%s' as the discriminator "
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"column due to mapped column %r; please apply the "
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"'typecolname' "
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"argument; this is available on "
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"ConcreteBase as '_concrete_discriminator_name'"
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% (typecolname, c)
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)
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colnames.add(c.key)
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m[c.key] = c
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types[c.key] = c.type
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colnamemaps[table] = m
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def col(name, table):
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try:
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return colnamemaps[table][name]
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except KeyError:
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if cast_nulls:
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return sql.cast(sql.null(), types[name]).label(name)
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else:
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return sql.type_coerce(sql.null(), types[name]).label(name)
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result = []
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for type_, table in table_map.items():
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if typecolname is not None:
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result.append(
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sql.select(
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*(
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[col(name, table) for name in colnames]
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+ [
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sql.literal_column(
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sql_util._quote_ddl_expr(type_)
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).label(typecolname)
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]
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)
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).select_from(table)
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)
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else:
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result.append(
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sql.select(
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*[col(name, table) for name in colnames]
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).select_from(table)
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)
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return sql.union_all(*result).alias(aliasname)
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def identity_key(*args, **kwargs):
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r"""Generate "identity key" tuples, as are used as keys in the
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:attr:`.Session.identity_map` dictionary.
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This function has several call styles:
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* ``identity_key(class, ident, identity_token=token)``
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This form receives a mapped class and a primary key scalar or
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tuple as an argument.
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E.g.::
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>>> identity_key(MyClass, (1, 2))
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(<class '__main__.MyClass'>, (1, 2), None)
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:param class: mapped class (must be a positional argument)
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:param ident: primary key, may be a scalar or tuple argument.
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:param identity_token: optional identity token
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.. versionadded:: 1.2 added identity_token
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* ``identity_key(instance=instance)``
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This form will produce the identity key for a given instance. The
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instance need not be persistent, only that its primary key attributes
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are populated (else the key will contain ``None`` for those missing
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values).
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E.g.::
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>>> instance = MyClass(1, 2)
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>>> identity_key(instance=instance)
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(<class '__main__.MyClass'>, (1, 2), None)
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In this form, the given instance is ultimately run though
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:meth:`_orm.Mapper.identity_key_from_instance`, which will have the
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effect of performing a database check for the corresponding row
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if the object is expired.
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:param instance: object instance (must be given as a keyword arg)
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* ``identity_key(class, row=row, identity_token=token)``
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This form is similar to the class/tuple form, except is passed a
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database result row as a :class:`.Row` object.
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E.g.::
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>>> row = engine.execute(\
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text("select * from table where a=1 and b=2")\
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).first()
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>>> identity_key(MyClass, row=row)
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(<class '__main__.MyClass'>, (1, 2), None)
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:param class: mapped class (must be a positional argument)
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:param row: :class:`.Row` row returned by a :class:`_engine.CursorResult`
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(must be given as a keyword arg)
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:param identity_token: optional identity token
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.. versionadded:: 1.2 added identity_token
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"""
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if args:
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row = None
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largs = len(args)
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if largs == 1:
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class_ = args[0]
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try:
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row = kwargs.pop("row")
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except KeyError:
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ident = kwargs.pop("ident")
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elif largs in (2, 3):
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class_, ident = args
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else:
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raise sa_exc.ArgumentError(
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"expected up to three positional arguments, " "got %s" % largs
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)
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identity_token = kwargs.pop("identity_token", None)
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if kwargs:
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raise sa_exc.ArgumentError(
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"unknown keyword arguments: %s" % ", ".join(kwargs)
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)
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mapper = class_mapper(class_)
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if row is None:
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return mapper.identity_key_from_primary_key(
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util.to_list(ident), identity_token=identity_token
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)
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else:
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return mapper.identity_key_from_row(
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row, identity_token=identity_token
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)
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else:
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instance = kwargs.pop("instance")
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if kwargs:
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raise sa_exc.ArgumentError(
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"unknown keyword arguments: %s" % ", ".join(kwargs.keys)
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)
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mapper = object_mapper(instance)
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return mapper.identity_key_from_instance(instance)
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class ORMAdapter(sql_util.ColumnAdapter):
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"""ColumnAdapter subclass which excludes adaptation of entities from
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non-matching mappers.
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"""
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def __init__(
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self,
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entity,
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equivalents=None,
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adapt_required=False,
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allow_label_resolve=True,
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anonymize_labels=False,
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):
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info = inspection.inspect(entity)
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self.mapper = info.mapper
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selectable = info.selectable
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is_aliased_class = info.is_aliased_class
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if is_aliased_class:
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self.aliased_class = entity
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else:
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self.aliased_class = None
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sql_util.ColumnAdapter.__init__(
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self,
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selectable,
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equivalents,
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adapt_required=adapt_required,
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allow_label_resolve=allow_label_resolve,
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anonymize_labels=anonymize_labels,
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include_fn=self._include_fn,
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)
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def _include_fn(self, elem):
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entity = elem._annotations.get("parentmapper", None)
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return not entity or entity.isa(self.mapper) or self.mapper.isa(entity)
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class AliasedClass(object):
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r"""Represents an "aliased" form of a mapped class for usage with Query.
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The ORM equivalent of a :func:`~sqlalchemy.sql.expression.alias`
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construct, this object mimics the mapped class using a
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``__getattr__`` scheme and maintains a reference to a
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real :class:`~sqlalchemy.sql.expression.Alias` object.
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A primary purpose of :class:`.AliasedClass` is to serve as an alternate
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within a SQL statement generated by the ORM, such that an existing
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mapped entity can be used in multiple contexts. A simple example::
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# find all pairs of users with the same name
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user_alias = aliased(User)
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session.query(User, user_alias).\
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join((user_alias, User.id > user_alias.id)).\
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filter(User.name == user_alias.name)
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:class:`.AliasedClass` is also capable of mapping an existing mapped
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class to an entirely new selectable, provided this selectable is column-
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compatible with the existing mapped selectable, and it can also be
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configured in a mapping as the target of a :func:`_orm.relationship`.
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See the links below for examples.
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The :class:`.AliasedClass` object is constructed typically using the
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:func:`_orm.aliased` function. It also is produced with additional
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configuration when using the :func:`_orm.with_polymorphic` function.
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The resulting object is an instance of :class:`.AliasedClass`.
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This object implements an attribute scheme which produces the
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same attribute and method interface as the original mapped
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class, allowing :class:`.AliasedClass` to be compatible
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with any attribute technique which works on the original class,
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including hybrid attributes (see :ref:`hybrids_toplevel`).
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The :class:`.AliasedClass` can be inspected for its underlying
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:class:`_orm.Mapper`, aliased selectable, and other information
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using :func:`_sa.inspect`::
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from sqlalchemy import inspect
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my_alias = aliased(MyClass)
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insp = inspect(my_alias)
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The resulting inspection object is an instance of :class:`.AliasedInsp`.
|
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|
|
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.. seealso::
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:func:`.aliased`
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:func:`.with_polymorphic`
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:ref:`relationship_aliased_class`
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:ref:`relationship_to_window_function`
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"""
|
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|
|
def __init__(
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self,
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mapped_class_or_ac,
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alias=None,
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name=None,
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flat=False,
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adapt_on_names=False,
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# TODO: None for default here?
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with_polymorphic_mappers=(),
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with_polymorphic_discriminator=None,
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base_alias=None,
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use_mapper_path=False,
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represents_outer_join=False,
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):
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insp = inspection.inspect(mapped_class_or_ac)
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mapper = insp.mapper
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nest_adapters = False
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if alias is None:
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if insp.is_aliased_class and insp.selectable._is_subquery:
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alias = insp.selectable.alias()
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else:
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alias = (
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mapper._with_polymorphic_selectable._anonymous_fromclause(
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name=name,
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flat=flat,
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)
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)
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elif insp.is_aliased_class:
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nest_adapters = True
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self._aliased_insp = AliasedInsp(
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self,
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insp,
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alias,
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name,
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with_polymorphic_mappers
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if with_polymorphic_mappers
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else mapper.with_polymorphic_mappers,
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with_polymorphic_discriminator
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|
if with_polymorphic_discriminator is not None
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else mapper.polymorphic_on,
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base_alias,
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use_mapper_path,
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adapt_on_names,
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represents_outer_join,
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nest_adapters,
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)
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self.__name__ = "AliasedClass_%s" % mapper.class_.__name__
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|
|
@classmethod
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|
def _reconstitute_from_aliased_insp(cls, aliased_insp):
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obj = cls.__new__(cls)
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obj.__name__ = "AliasedClass_%s" % aliased_insp.mapper.class_.__name__
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obj._aliased_insp = aliased_insp
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|
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if aliased_insp._is_with_polymorphic:
|
|
for sub_aliased_insp in aliased_insp._with_polymorphic_entities:
|
|
if sub_aliased_insp is not aliased_insp:
|
|
ent = AliasedClass._reconstitute_from_aliased_insp(
|
|
sub_aliased_insp
|
|
)
|
|
setattr(obj, sub_aliased_insp.class_.__name__, ent)
|
|
|
|
return obj
|
|
|
|
def __getattr__(self, key):
|
|
try:
|
|
_aliased_insp = self.__dict__["_aliased_insp"]
|
|
except KeyError:
|
|
raise AttributeError()
|
|
else:
|
|
target = _aliased_insp._target
|
|
# maintain all getattr mechanics
|
|
attr = getattr(target, key)
|
|
|
|
# attribute is a method, that will be invoked against a
|
|
# "self"; so just return a new method with the same function and
|
|
# new self
|
|
if hasattr(attr, "__call__") and hasattr(attr, "__self__"):
|
|
return types.MethodType(attr.__func__, self)
|
|
|
|
# attribute is a descriptor, that will be invoked against a
|
|
# "self"; so invoke the descriptor against this self
|
|
if hasattr(attr, "__get__"):
|
|
attr = attr.__get__(None, self)
|
|
|
|
# attributes within the QueryableAttribute system will want this
|
|
# to be invoked so the object can be adapted
|
|
if hasattr(attr, "adapt_to_entity"):
|
|
attr = attr.adapt_to_entity(_aliased_insp)
|
|
setattr(self, key, attr)
|
|
|
|
return attr
|
|
|
|
def _get_from_serialized(self, key, mapped_class, aliased_insp):
|
|
# this method is only used in terms of the
|
|
# sqlalchemy.ext.serializer extension
|
|
attr = getattr(mapped_class, key)
|
|
if hasattr(attr, "__call__") and hasattr(attr, "__self__"):
|
|
return types.MethodType(attr.__func__, self)
|
|
|
|
# attribute is a descriptor, that will be invoked against a
|
|
# "self"; so invoke the descriptor against this self
|
|
if hasattr(attr, "__get__"):
|
|
attr = attr.__get__(None, self)
|
|
|
|
# attributes within the QueryableAttribute system will want this
|
|
# to be invoked so the object can be adapted
|
|
if hasattr(attr, "adapt_to_entity"):
|
|
aliased_insp._weak_entity = weakref.ref(self)
|
|
attr = attr.adapt_to_entity(aliased_insp)
|
|
setattr(self, key, attr)
|
|
|
|
return attr
|
|
|
|
def __repr__(self):
|
|
return "<AliasedClass at 0x%x; %s>" % (
|
|
id(self),
|
|
self._aliased_insp._target.__name__,
|
|
)
|
|
|
|
def __str__(self):
|
|
return str(self._aliased_insp)
|
|
|
|
|
|
class AliasedInsp(
|
|
ORMEntityColumnsClauseRole,
|
|
ORMFromClauseRole,
|
|
sql_base.MemoizedHasCacheKey,
|
|
InspectionAttr,
|
|
):
|
|
"""Provide an inspection interface for an
|
|
:class:`.AliasedClass` object.
|
|
|
|
The :class:`.AliasedInsp` object is returned
|
|
given an :class:`.AliasedClass` using the
|
|
:func:`_sa.inspect` function::
|
|
|
|
from sqlalchemy import inspect
|
|
from sqlalchemy.orm import aliased
|
|
|
|
my_alias = aliased(MyMappedClass)
|
|
insp = inspect(my_alias)
|
|
|
|
Attributes on :class:`.AliasedInsp`
|
|
include:
|
|
|
|
* ``entity`` - the :class:`.AliasedClass` represented.
|
|
* ``mapper`` - the :class:`_orm.Mapper` mapping the underlying class.
|
|
* ``selectable`` - the :class:`_expression.Alias`
|
|
construct which ultimately
|
|
represents an aliased :class:`_schema.Table` or
|
|
:class:`_expression.Select`
|
|
construct.
|
|
* ``name`` - the name of the alias. Also is used as the attribute
|
|
name when returned in a result tuple from :class:`_query.Query`.
|
|
* ``with_polymorphic_mappers`` - collection of :class:`_orm.Mapper`
|
|
objects
|
|
indicating all those mappers expressed in the select construct
|
|
for the :class:`.AliasedClass`.
|
|
* ``polymorphic_on`` - an alternate column or SQL expression which
|
|
will be used as the "discriminator" for a polymorphic load.
|
|
|
|
.. seealso::
|
|
|
|
:ref:`inspection_toplevel`
|
|
|
|
"""
|
|
|
|
_cache_key_traversal = [
|
|
("name", visitors.ExtendedInternalTraversal.dp_string),
|
|
("_adapt_on_names", visitors.ExtendedInternalTraversal.dp_boolean),
|
|
("_use_mapper_path", visitors.ExtendedInternalTraversal.dp_boolean),
|
|
("_target", visitors.ExtendedInternalTraversal.dp_inspectable),
|
|
("selectable", visitors.ExtendedInternalTraversal.dp_clauseelement),
|
|
(
|
|
"with_polymorphic_mappers",
|
|
visitors.InternalTraversal.dp_has_cache_key_list,
|
|
),
|
|
("polymorphic_on", visitors.InternalTraversal.dp_clauseelement),
|
|
]
|
|
|
|
def __init__(
|
|
self,
|
|
entity,
|
|
inspected,
|
|
selectable,
|
|
name,
|
|
with_polymorphic_mappers,
|
|
polymorphic_on,
|
|
_base_alias,
|
|
_use_mapper_path,
|
|
adapt_on_names,
|
|
represents_outer_join,
|
|
nest_adapters,
|
|
):
|
|
|
|
mapped_class_or_ac = inspected.entity
|
|
mapper = inspected.mapper
|
|
|
|
self._weak_entity = weakref.ref(entity)
|
|
self.mapper = mapper
|
|
self.selectable = (
|
|
self.persist_selectable
|
|
) = self.local_table = selectable
|
|
self.name = name
|
|
self.polymorphic_on = polymorphic_on
|
|
self._base_alias = weakref.ref(_base_alias or self)
|
|
self._use_mapper_path = _use_mapper_path
|
|
self.represents_outer_join = represents_outer_join
|
|
self._nest_adapters = nest_adapters
|
|
|
|
if with_polymorphic_mappers:
|
|
self._is_with_polymorphic = True
|
|
self.with_polymorphic_mappers = with_polymorphic_mappers
|
|
self._with_polymorphic_entities = []
|
|
for poly in self.with_polymorphic_mappers:
|
|
if poly is not mapper:
|
|
ent = AliasedClass(
|
|
poly.class_,
|
|
selectable,
|
|
base_alias=self,
|
|
adapt_on_names=adapt_on_names,
|
|
use_mapper_path=_use_mapper_path,
|
|
)
|
|
|
|
setattr(self.entity, poly.class_.__name__, ent)
|
|
self._with_polymorphic_entities.append(ent._aliased_insp)
|
|
|
|
else:
|
|
self._is_with_polymorphic = False
|
|
self.with_polymorphic_mappers = [mapper]
|
|
|
|
self._adapter = sql_util.ColumnAdapter(
|
|
selectable,
|
|
equivalents=mapper._equivalent_columns,
|
|
adapt_on_names=adapt_on_names,
|
|
anonymize_labels=True,
|
|
# make sure the adapter doesn't try to grab other tables that
|
|
# are not even the thing we are mapping, such as embedded
|
|
# selectables in subqueries or CTEs. See issue #6060
|
|
adapt_from_selectables={
|
|
m.selectable
|
|
for m in self.with_polymorphic_mappers
|
|
if not adapt_on_names
|
|
},
|
|
)
|
|
|
|
if nest_adapters:
|
|
self._adapter = inspected._adapter.wrap(self._adapter)
|
|
|
|
self._adapt_on_names = adapt_on_names
|
|
self._target = mapped_class_or_ac
|
|
# self._target = mapper.class_ # mapped_class_or_ac
|
|
|
|
@property
|
|
def entity(self):
|
|
# to eliminate reference cycles, the AliasedClass is held weakly.
|
|
# this produces some situations where the AliasedClass gets lost,
|
|
# particularly when one is created internally and only the AliasedInsp
|
|
# is passed around.
|
|
# to work around this case, we just generate a new one when we need
|
|
# it, as it is a simple class with very little initial state on it.
|
|
ent = self._weak_entity()
|
|
if ent is None:
|
|
ent = AliasedClass._reconstitute_from_aliased_insp(self)
|
|
self._weak_entity = weakref.ref(ent)
|
|
return ent
|
|
|
|
is_aliased_class = True
|
|
"always returns True"
|
|
|
|
@util.memoized_instancemethod
|
|
def __clause_element__(self):
|
|
return self.selectable._annotate(
|
|
{
|
|
"parentmapper": self.mapper,
|
|
"parententity": self,
|
|
"entity_namespace": self,
|
|
}
|
|
)._set_propagate_attrs(
|
|
{"compile_state_plugin": "orm", "plugin_subject": self}
|
|
)
|
|
|
|
@property
|
|
def entity_namespace(self):
|
|
return self.entity
|
|
|
|
@property
|
|
def class_(self):
|
|
"""Return the mapped class ultimately represented by this
|
|
:class:`.AliasedInsp`."""
|
|
return self.mapper.class_
|
|
|
|
@property
|
|
def _path_registry(self):
|
|
if self._use_mapper_path:
|
|
return self.mapper._path_registry
|
|
else:
|
|
return PathRegistry.per_mapper(self)
|
|
|
|
def __getstate__(self):
|
|
return {
|
|
"entity": self.entity,
|
|
"mapper": self.mapper,
|
|
"alias": self.selectable,
|
|
"name": self.name,
|
|
"adapt_on_names": self._adapt_on_names,
|
|
"with_polymorphic_mappers": self.with_polymorphic_mappers,
|
|
"with_polymorphic_discriminator": self.polymorphic_on,
|
|
"base_alias": self._base_alias(),
|
|
"use_mapper_path": self._use_mapper_path,
|
|
"represents_outer_join": self.represents_outer_join,
|
|
"nest_adapters": self._nest_adapters,
|
|
}
|
|
|
|
def __setstate__(self, state):
|
|
self.__init__(
|
|
state["entity"],
|
|
state["mapper"],
|
|
state["alias"],
|
|
state["name"],
|
|
state["with_polymorphic_mappers"],
|
|
state["with_polymorphic_discriminator"],
|
|
state["base_alias"],
|
|
state["use_mapper_path"],
|
|
state["adapt_on_names"],
|
|
state["represents_outer_join"],
|
|
state["nest_adapters"],
|
|
)
|
|
|
|
def _adapt_element(self, elem, key=None):
|
|
d = {
|
|
"parententity": self,
|
|
"parentmapper": self.mapper,
|
|
}
|
|
if key:
|
|
d["proxy_key"] = key
|
|
return (
|
|
self._adapter.traverse(elem)
|
|
._annotate(d)
|
|
._set_propagate_attrs(
|
|
{"compile_state_plugin": "orm", "plugin_subject": self}
|
|
)
|
|
)
|
|
|
|
def _entity_for_mapper(self, mapper):
|
|
self_poly = self.with_polymorphic_mappers
|
|
if mapper in self_poly:
|
|
if mapper is self.mapper:
|
|
return self
|
|
else:
|
|
return getattr(
|
|
self.entity, mapper.class_.__name__
|
|
)._aliased_insp
|
|
elif mapper.isa(self.mapper):
|
|
return self
|
|
else:
|
|
assert False, "mapper %s doesn't correspond to %s" % (mapper, self)
|
|
|
|
@util.memoized_property
|
|
def _get_clause(self):
|
|
onclause, replacemap = self.mapper._get_clause
|
|
return (
|
|
self._adapter.traverse(onclause),
|
|
{
|
|
self._adapter.traverse(col): param
|
|
for col, param in replacemap.items()
|
|
},
|
|
)
|
|
|
|
@util.memoized_property
|
|
def _memoized_values(self):
|
|
return {}
|
|
|
|
@util.memoized_property
|
|
def _all_column_expressions(self):
|
|
if self._is_with_polymorphic:
|
|
cols_plus_keys = self.mapper._columns_plus_keys(
|
|
[ent.mapper for ent in self._with_polymorphic_entities]
|
|
)
|
|
else:
|
|
cols_plus_keys = self.mapper._columns_plus_keys()
|
|
|
|
cols_plus_keys = [
|
|
(key, self._adapt_element(col)) for key, col in cols_plus_keys
|
|
]
|
|
|
|
return ColumnCollection(cols_plus_keys)
|
|
|
|
def _memo(self, key, callable_, *args, **kw):
|
|
if key in self._memoized_values:
|
|
return self._memoized_values[key]
|
|
else:
|
|
self._memoized_values[key] = value = callable_(*args, **kw)
|
|
return value
|
|
|
|
def __repr__(self):
|
|
if self.with_polymorphic_mappers:
|
|
with_poly = "(%s)" % ", ".join(
|
|
mp.class_.__name__ for mp in self.with_polymorphic_mappers
|
|
)
|
|
else:
|
|
with_poly = ""
|
|
return "<AliasedInsp at 0x%x; %s%s>" % (
|
|
id(self),
|
|
self.class_.__name__,
|
|
with_poly,
|
|
)
|
|
|
|
def __str__(self):
|
|
if self._is_with_polymorphic:
|
|
return "with_polymorphic(%s, [%s])" % (
|
|
self._target.__name__,
|
|
", ".join(
|
|
mp.class_.__name__
|
|
for mp in self.with_polymorphic_mappers
|
|
if mp is not self.mapper
|
|
),
|
|
)
|
|
else:
|
|
return "aliased(%s)" % (self._target.__name__,)
|
|
|
|
|
|
class _WrapUserEntity(object):
|
|
"""A wrapper used within the loader_criteria lambda caller so that
|
|
we can bypass declared_attr descriptors on unmapped mixins, which
|
|
normally emit a warning for such use.
|
|
|
|
might also be useful for other per-lambda instrumentations should
|
|
the need arise.
|
|
|
|
"""
|
|
|
|
__slots__ = ("subject",)
|
|
|
|
def __init__(self, subject):
|
|
self.subject = subject
|
|
|
|
@util.preload_module("sqlalchemy.orm.decl_api")
|
|
def __getattribute__(self, name):
|
|
decl_api = util.preloaded.orm.decl_api
|
|
|
|
subject = object.__getattribute__(self, "subject")
|
|
if name in subject.__dict__ and isinstance(
|
|
subject.__dict__[name], decl_api.declared_attr
|
|
):
|
|
return subject.__dict__[name].fget(subject)
|
|
else:
|
|
return getattr(subject, name)
|
|
|
|
|
|
class LoaderCriteriaOption(CriteriaOption):
|
|
"""Add additional WHERE criteria to the load for all occurrences of
|
|
a particular entity.
|
|
|
|
:class:`_orm.LoaderCriteriaOption` is invoked using the
|
|
:func:`_orm.with_loader_criteria` function; see that function for
|
|
details.
|
|
|
|
.. versionadded:: 1.4
|
|
|
|
"""
|
|
|
|
_traverse_internals = [
|
|
("root_entity", visitors.ExtendedInternalTraversal.dp_plain_obj),
|
|
("entity", visitors.ExtendedInternalTraversal.dp_has_cache_key),
|
|
("where_criteria", visitors.InternalTraversal.dp_clauseelement),
|
|
("include_aliases", visitors.InternalTraversal.dp_boolean),
|
|
("propagate_to_loaders", visitors.InternalTraversal.dp_boolean),
|
|
]
|
|
|
|
def __init__(
|
|
self,
|
|
entity_or_base,
|
|
where_criteria,
|
|
loader_only=False,
|
|
include_aliases=False,
|
|
propagate_to_loaders=True,
|
|
track_closure_variables=True,
|
|
):
|
|
"""Add additional WHERE criteria to the load for all occurrences of
|
|
a particular entity.
|
|
|
|
.. versionadded:: 1.4
|
|
|
|
The :func:`_orm.with_loader_criteria` option is intended to add
|
|
limiting criteria to a particular kind of entity in a query,
|
|
**globally**, meaning it will apply to the entity as it appears
|
|
in the SELECT query as well as within any subqueries, join
|
|
conditions, and relationship loads, including both eager and lazy
|
|
loaders, without the need for it to be specified in any particular
|
|
part of the query. The rendering logic uses the same system used by
|
|
single table inheritance to ensure a certain discriminator is applied
|
|
to a table.
|
|
|
|
E.g., using :term:`2.0-style` queries, we can limit the way the
|
|
``User.addresses`` collection is loaded, regardless of the kind
|
|
of loading used::
|
|
|
|
from sqlalchemy.orm import with_loader_criteria
|
|
|
|
stmt = select(User).options(
|
|
selectinload(User.addresses),
|
|
with_loader_criteria(Address, Address.email_address != 'foo'))
|
|
)
|
|
|
|
Above, the "selectinload" for ``User.addresses`` will apply the
|
|
given filtering criteria to the WHERE clause.
|
|
|
|
Another example, where the filtering will be applied to the
|
|
ON clause of the join, in this example using :term:`1.x style`
|
|
queries::
|
|
|
|
q = session.query(User).outerjoin(User.addresses).options(
|
|
with_loader_criteria(Address, Address.email_address != 'foo'))
|
|
)
|
|
|
|
The primary purpose of :func:`_orm.with_loader_criteria` is to use
|
|
it in the :meth:`_orm.SessionEvents.do_orm_execute` event handler
|
|
to ensure that all occurrences of a particular entity are filtered
|
|
in a certain way, such as filtering for access control roles. It
|
|
also can be used to apply criteria to relationship loads. In the
|
|
example below, we can apply a certain set of rules to all queries
|
|
emitted by a particular :class:`_orm.Session`::
|
|
|
|
session = Session(bind=engine)
|
|
|
|
@event.listens_for("do_orm_execute", session)
|
|
def _add_filtering_criteria(execute_state):
|
|
|
|
if (
|
|
execute_state.is_select
|
|
and not execute_state.is_column_load
|
|
and not execute_state.is_relationship_load
|
|
):
|
|
execute_state.statement = execute_state.statement.options(
|
|
with_loader_criteria(
|
|
SecurityRole,
|
|
lambda cls: cls.role.in_(['some_role']),
|
|
include_aliases=True
|
|
)
|
|
)
|
|
|
|
In the above example, the :meth:`_orm.SessionEvents.do_orm_execute`
|
|
event will intercept all queries emitted using the
|
|
:class:`_orm.Session`. For those queries which are SELECT statements
|
|
and are not attribute or relationship loads a custom
|
|
:func:`_orm.with_loader_criteria` option is added to the query. The
|
|
:func:`_orm.with_loader_criteria` option will be used in the given
|
|
statement and will also be automatically propagated to all relationship
|
|
loads that descend from this query.
|
|
|
|
The criteria argument given is a ``lambda`` that accepts a ``cls``
|
|
argument. The given class will expand to include all mapped subclass
|
|
and need not itself be a mapped class.
|
|
|
|
.. tip::
|
|
|
|
When using :func:`_orm.with_loader_criteria` option in
|
|
conjunction with the :func:`_orm.contains_eager` loader option,
|
|
it's important to note that :func:`_orm.with_loader_criteria` only
|
|
affects the part of the query that determines what SQL is rendered
|
|
in terms of the WHERE and FROM clauses. The
|
|
:func:`_orm.contains_eager` option does not affect the rendering of
|
|
the SELECT statement outside of the columns clause, so does not have
|
|
any interaction with the :func:`_orm.with_loader_criteria` option.
|
|
However, the way things "work" is that :func:`_orm.contains_eager`
|
|
is meant to be used with a query that is already selecting from the
|
|
additional entities in some way, where
|
|
:func:`_orm.with_loader_criteria` can apply it's additional
|
|
criteria.
|
|
|
|
In the example below, assuming a mapping relationship as
|
|
``A -> A.bs -> B``, the given :func:`_orm.with_loader_criteria`
|
|
option will affect the way in which the JOIN is rendered::
|
|
|
|
stmt = select(A).join(A.bs).options(
|
|
contains_eager(A.bs),
|
|
with_loader_criteria(B, B.flag == 1)
|
|
)
|
|
|
|
Above, the given :func:`_orm.with_loader_criteria` option will
|
|
affect the ON clause of the JOIN that is specified by
|
|
``.join(A.bs)``, so is applied as expected. The
|
|
:func:`_orm.contains_eager` option has the effect that columns from
|
|
``B`` are added to the columns clause::
|
|
|
|
SELECT
|
|
b.id, b.a_id, b.data, b.flag,
|
|
a.id AS id_1,
|
|
a.data AS data_1
|
|
FROM a JOIN b ON a.id = b.a_id AND b.flag = :flag_1
|
|
|
|
|
|
The use of the :func:`_orm.contains_eager` option within the above
|
|
statement has no effect on the behavior of the
|
|
:func:`_orm.with_loader_criteria` option. If the
|
|
:func:`_orm.contains_eager` option were omitted, the SQL would be
|
|
the same as regards the FROM and WHERE clauses, where
|
|
:func:`_orm.with_loader_criteria` continues to add its criteria to
|
|
the ON clause of the JOIN. The addition of
|
|
:func:`_orm.contains_eager` only affects the columns clause, in that
|
|
additional columns against ``b`` are added which are then consumed
|
|
by the ORM to produce ``B`` instances.
|
|
|
|
.. warning:: The use of a lambda inside of the call to
|
|
:func:`_orm.with_loader_criteria` is only invoked **once per unique
|
|
class**. Custom functions should not be invoked within this lambda.
|
|
See :ref:`engine_lambda_caching` for an overview of the "lambda SQL"
|
|
feature, which is for advanced use only.
|
|
|
|
:param entity_or_base: a mapped class, or a class that is a super
|
|
class of a particular set of mapped classes, to which the rule
|
|
will apply.
|
|
|
|
:param where_criteria: a Core SQL expression that applies limiting
|
|
criteria. This may also be a "lambda:" or Python function that
|
|
accepts a target class as an argument, when the given class is
|
|
a base with many different mapped subclasses.
|
|
|
|
.. note:: To support pickling, use a module-level Python function to
|
|
produce the SQL expression instead of a lambda or a fixed SQL
|
|
expression, which tend to not be picklable.
|
|
|
|
:param include_aliases: if True, apply the rule to :func:`_orm.aliased`
|
|
constructs as well.
|
|
|
|
:param propagate_to_loaders: defaults to True, apply to relationship
|
|
loaders such as lazy loaders. This indicates that the
|
|
option object itself including SQL expression is carried along with
|
|
each loaded instance. Set to ``False`` to prevent the object from
|
|
being assigned to individual instances.
|
|
|
|
.. seealso::
|
|
|
|
:ref:`examples_session_orm_events` - includes examples of using
|
|
:func:`_orm.with_loader_criteria`.
|
|
|
|
:ref:`do_orm_execute_global_criteria` - basic example on how to
|
|
combine :func:`_orm.with_loader_criteria` with the
|
|
:meth:`_orm.SessionEvents.do_orm_execute` event.
|
|
|
|
:param track_closure_variables: when False, closure variables inside
|
|
of a lambda expression will not be used as part of
|
|
any cache key. This allows more complex expressions to be used
|
|
inside of a lambda expression but requires that the lambda ensures
|
|
it returns the identical SQL every time given a particular class.
|
|
|
|
.. versionadded:: 1.4.0b2
|
|
|
|
"""
|
|
entity = inspection.inspect(entity_or_base, False)
|
|
if entity is None:
|
|
self.root_entity = entity_or_base
|
|
self.entity = None
|
|
else:
|
|
self.root_entity = None
|
|
self.entity = entity
|
|
|
|
self._where_crit_orig = where_criteria
|
|
if callable(where_criteria):
|
|
self.deferred_where_criteria = True
|
|
self.where_criteria = lambdas.DeferredLambdaElement(
|
|
where_criteria,
|
|
roles.WhereHavingRole,
|
|
lambda_args=(
|
|
_WrapUserEntity(
|
|
self.root_entity
|
|
if self.root_entity is not None
|
|
else self.entity.entity,
|
|
),
|
|
),
|
|
opts=lambdas.LambdaOptions(
|
|
track_closure_variables=track_closure_variables
|
|
),
|
|
)
|
|
else:
|
|
self.deferred_where_criteria = False
|
|
self.where_criteria = coercions.expect(
|
|
roles.WhereHavingRole, where_criteria
|
|
)
|
|
|
|
self.include_aliases = include_aliases
|
|
self.propagate_to_loaders = propagate_to_loaders
|
|
|
|
@classmethod
|
|
def _unreduce(
|
|
cls, entity, where_criteria, include_aliases, propagate_to_loaders
|
|
):
|
|
return LoaderCriteriaOption(
|
|
entity,
|
|
where_criteria,
|
|
include_aliases=include_aliases,
|
|
propagate_to_loaders=propagate_to_loaders,
|
|
)
|
|
|
|
def __reduce__(self):
|
|
return (
|
|
LoaderCriteriaOption._unreduce,
|
|
(
|
|
self.entity.class_ if self.entity else self.root_entity,
|
|
self._where_crit_orig,
|
|
self.include_aliases,
|
|
self.propagate_to_loaders,
|
|
),
|
|
)
|
|
|
|
def _all_mappers(self):
|
|
|
|
if self.entity:
|
|
for ent in self.entity.mapper.self_and_descendants:
|
|
yield ent
|
|
else:
|
|
stack = list(self.root_entity.__subclasses__())
|
|
while stack:
|
|
subclass = stack.pop(0)
|
|
ent = inspection.inspect(subclass, raiseerr=False)
|
|
if ent:
|
|
for mp in ent.mapper.self_and_descendants:
|
|
yield mp
|
|
else:
|
|
stack.extend(subclass.__subclasses__())
|
|
|
|
def _should_include(self, compile_state):
|
|
if (
|
|
compile_state.select_statement._annotations.get(
|
|
"for_loader_criteria", None
|
|
)
|
|
is self
|
|
):
|
|
return False
|
|
return True
|
|
|
|
def _resolve_where_criteria(self, ext_info):
|
|
if self.deferred_where_criteria:
|
|
crit = self.where_criteria._resolve_with_args(ext_info.entity)
|
|
else:
|
|
crit = self.where_criteria
|
|
return sql_util._deep_annotate(
|
|
crit, {"for_loader_criteria": self}, detect_subquery_cols=True
|
|
)
|
|
|
|
def process_compile_state_replaced_entities(
|
|
self, compile_state, mapper_entities
|
|
):
|
|
return self.process_compile_state(compile_state)
|
|
|
|
def process_compile_state(self, compile_state):
|
|
"""Apply a modification to a given :class:`.CompileState`."""
|
|
|
|
# if options to limit the criteria to immediate query only,
|
|
# use compile_state.attributes instead
|
|
|
|
if compile_state.compile_options._with_polymorphic_adapt_map:
|
|
util.warn(
|
|
"The with_loader_criteria() function may not work "
|
|
"correctly with the legacy Query.with_polymorphic() feature. "
|
|
"Please migrate code to use the with_polymorphic() standalone "
|
|
"function before using with_loader_criteria()."
|
|
)
|
|
self.get_global_criteria(compile_state.global_attributes)
|
|
|
|
def get_global_criteria(self, attributes):
|
|
for mp in self._all_mappers():
|
|
load_criteria = attributes.setdefault(
|
|
("additional_entity_criteria", mp), []
|
|
)
|
|
|
|
load_criteria.append(self)
|
|
|
|
|
|
inspection._inspects(AliasedClass)(lambda target: target._aliased_insp)
|
|
inspection._inspects(AliasedInsp)(lambda target: target)
|
|
|
|
|
|
def aliased(element, alias=None, name=None, flat=False, adapt_on_names=False):
|
|
"""Produce an alias of the given element, usually an :class:`.AliasedClass`
|
|
instance.
|
|
|
|
E.g.::
|
|
|
|
my_alias = aliased(MyClass)
|
|
|
|
session.query(MyClass, my_alias).filter(MyClass.id > my_alias.id)
|
|
|
|
The :func:`.aliased` function is used to create an ad-hoc mapping of a
|
|
mapped class to a new selectable. By default, a selectable is generated
|
|
from the normally mapped selectable (typically a :class:`_schema.Table`
|
|
) using the
|
|
:meth:`_expression.FromClause.alias` method. However, :func:`.aliased`
|
|
can also be
|
|
used to link the class to a new :func:`_expression.select` statement.
|
|
Also, the :func:`.with_polymorphic` function is a variant of
|
|
:func:`.aliased` that is intended to specify a so-called "polymorphic
|
|
selectable", that corresponds to the union of several joined-inheritance
|
|
subclasses at once.
|
|
|
|
For convenience, the :func:`.aliased` function also accepts plain
|
|
:class:`_expression.FromClause` constructs, such as a
|
|
:class:`_schema.Table` or
|
|
:func:`_expression.select` construct. In those cases, the
|
|
:meth:`_expression.FromClause.alias`
|
|
method is called on the object and the new
|
|
:class:`_expression.Alias` object returned. The returned
|
|
:class:`_expression.Alias` is not
|
|
ORM-mapped in this case.
|
|
|
|
.. seealso::
|
|
|
|
:ref:`tutorial_orm_entity_aliases` - in the :ref:`unified_tutorial`
|
|
|
|
:ref:`orm_queryguide_orm_aliases` - in the :ref:`queryguide_toplevel`
|
|
|
|
:param element: element to be aliased. Is normally a mapped class,
|
|
but for convenience can also be a :class:`_expression.FromClause`
|
|
element.
|
|
|
|
:param alias: Optional selectable unit to map the element to. This is
|
|
usually used to link the object to a subquery, and should be an aliased
|
|
select construct as one would produce from the
|
|
:meth:`_query.Query.subquery` method or
|
|
the :meth:`_expression.Select.subquery` or
|
|
:meth:`_expression.Select.alias` methods of the :func:`_expression.select`
|
|
construct.
|
|
|
|
:param name: optional string name to use for the alias, if not specified
|
|
by the ``alias`` parameter. The name, among other things, forms the
|
|
attribute name that will be accessible via tuples returned by a
|
|
:class:`_query.Query` object. Not supported when creating aliases
|
|
of :class:`_sql.Join` objects.
|
|
|
|
:param flat: Boolean, will be passed through to the
|
|
:meth:`_expression.FromClause.alias` call so that aliases of
|
|
:class:`_expression.Join` objects will alias the individual tables
|
|
inside the join, rather than creating a subquery. This is generally
|
|
supported by all modern databases with regards to right-nested joins
|
|
and generally produces more efficient queries.
|
|
|
|
:param adapt_on_names: if True, more liberal "matching" will be used when
|
|
mapping the mapped columns of the ORM entity to those of the
|
|
given selectable - a name-based match will be performed if the
|
|
given selectable doesn't otherwise have a column that corresponds
|
|
to one on the entity. The use case for this is when associating
|
|
an entity with some derived selectable such as one that uses
|
|
aggregate functions::
|
|
|
|
class UnitPrice(Base):
|
|
__tablename__ = 'unit_price'
|
|
...
|
|
unit_id = Column(Integer)
|
|
price = Column(Numeric)
|
|
|
|
aggregated_unit_price = Session.query(
|
|
func.sum(UnitPrice.price).label('price')
|
|
).group_by(UnitPrice.unit_id).subquery()
|
|
|
|
aggregated_unit_price = aliased(UnitPrice,
|
|
alias=aggregated_unit_price, adapt_on_names=True)
|
|
|
|
Above, functions on ``aggregated_unit_price`` which refer to
|
|
``.price`` will return the
|
|
``func.sum(UnitPrice.price).label('price')`` column, as it is
|
|
matched on the name "price". Ordinarily, the "price" function
|
|
wouldn't have any "column correspondence" to the actual
|
|
``UnitPrice.price`` column as it is not a proxy of the original.
|
|
|
|
"""
|
|
if isinstance(element, expression.FromClause):
|
|
if adapt_on_names:
|
|
raise sa_exc.ArgumentError(
|
|
"adapt_on_names only applies to ORM elements"
|
|
)
|
|
if name:
|
|
return element.alias(name=name, flat=flat)
|
|
else:
|
|
return coercions.expect(
|
|
roles.AnonymizedFromClauseRole, element, flat=flat
|
|
)
|
|
else:
|
|
return AliasedClass(
|
|
element,
|
|
alias=alias,
|
|
flat=flat,
|
|
name=name,
|
|
adapt_on_names=adapt_on_names,
|
|
)
|
|
|
|
|
|
def with_polymorphic(
|
|
base,
|
|
classes,
|
|
selectable=False,
|
|
flat=False,
|
|
polymorphic_on=None,
|
|
aliased=False,
|
|
adapt_on_names=False,
|
|
innerjoin=False,
|
|
_use_mapper_path=False,
|
|
_existing_alias=None,
|
|
):
|
|
"""Produce an :class:`.AliasedClass` construct which specifies
|
|
columns for descendant mappers of the given base.
|
|
|
|
Using this method will ensure that each descendant mapper's
|
|
tables are included in the FROM clause, and will allow filter()
|
|
criterion to be used against those tables. The resulting
|
|
instances will also have those columns already loaded so that
|
|
no "post fetch" of those columns will be required.
|
|
|
|
.. seealso::
|
|
|
|
:ref:`with_polymorphic` - full discussion of
|
|
:func:`_orm.with_polymorphic`.
|
|
|
|
:param base: Base class to be aliased.
|
|
|
|
:param classes: a single class or mapper, or list of
|
|
class/mappers, which inherit from the base class.
|
|
Alternatively, it may also be the string ``'*'``, in which case
|
|
all descending mapped classes will be added to the FROM clause.
|
|
|
|
:param aliased: when True, the selectable will be aliased. For a
|
|
JOIN, this means the JOIN will be SELECTed from inside of a subquery
|
|
unless the :paramref:`_orm.with_polymorphic.flat` flag is set to
|
|
True, which is recommended for simpler use cases.
|
|
|
|
:param flat: Boolean, will be passed through to the
|
|
:meth:`_expression.FromClause.alias` call so that aliases of
|
|
:class:`_expression.Join` objects will alias the individual tables
|
|
inside the join, rather than creating a subquery. This is generally
|
|
supported by all modern databases with regards to right-nested joins
|
|
and generally produces more efficient queries. Setting this flag is
|
|
recommended as long as the resulting SQL is functional.
|
|
|
|
:param selectable: a table or subquery that will
|
|
be used in place of the generated FROM clause. This argument is
|
|
required if any of the desired classes use concrete table
|
|
inheritance, since SQLAlchemy currently cannot generate UNIONs
|
|
among tables automatically. If used, the ``selectable`` argument
|
|
must represent the full set of tables and columns mapped by every
|
|
mapped class. Otherwise, the unaccounted mapped columns will
|
|
result in their table being appended directly to the FROM clause
|
|
which will usually lead to incorrect results.
|
|
|
|
When left at its default value of ``False``, the polymorphic
|
|
selectable assigned to the base mapper is used for selecting rows.
|
|
However, it may also be passed as ``None``, which will bypass the
|
|
configured polymorphic selectable and instead construct an ad-hoc
|
|
selectable for the target classes given; for joined table inheritance
|
|
this will be a join that includes all target mappers and their
|
|
subclasses.
|
|
|
|
:param polymorphic_on: a column to be used as the "discriminator"
|
|
column for the given selectable. If not given, the polymorphic_on
|
|
attribute of the base classes' mapper will be used, if any. This
|
|
is useful for mappings that don't have polymorphic loading
|
|
behavior by default.
|
|
|
|
:param innerjoin: if True, an INNER JOIN will be used. This should
|
|
only be specified if querying for one specific subtype only
|
|
|
|
:param adapt_on_names: Passes through the
|
|
:paramref:`_orm.aliased.adapt_on_names`
|
|
parameter to the aliased object. This may be useful in situations where
|
|
the given selectable is not directly related to the existing mapped
|
|
selectable.
|
|
|
|
.. versionadded:: 1.4.33
|
|
|
|
"""
|
|
primary_mapper = _class_to_mapper(base)
|
|
|
|
if selectable not in (None, False) and flat:
|
|
raise sa_exc.ArgumentError(
|
|
"the 'flat' and 'selectable' arguments cannot be passed "
|
|
"simultaneously to with_polymorphic()"
|
|
)
|
|
|
|
if _existing_alias:
|
|
assert _existing_alias.mapper is primary_mapper
|
|
classes = util.to_set(classes)
|
|
new_classes = set(
|
|
[mp.class_ for mp in _existing_alias.with_polymorphic_mappers]
|
|
)
|
|
if classes == new_classes:
|
|
return _existing_alias
|
|
else:
|
|
classes = classes.union(new_classes)
|
|
mappers, selectable = primary_mapper._with_polymorphic_args(
|
|
classes, selectable, innerjoin=innerjoin
|
|
)
|
|
if aliased or flat:
|
|
selectable = selectable._anonymous_fromclause(flat=flat)
|
|
return AliasedClass(
|
|
base,
|
|
selectable,
|
|
adapt_on_names=adapt_on_names,
|
|
with_polymorphic_mappers=mappers,
|
|
with_polymorphic_discriminator=polymorphic_on,
|
|
use_mapper_path=_use_mapper_path,
|
|
represents_outer_join=not innerjoin,
|
|
)
|
|
|
|
|
|
@inspection._self_inspects
|
|
class Bundle(
|
|
ORMColumnsClauseRole,
|
|
SupportsCloneAnnotations,
|
|
sql_base.MemoizedHasCacheKey,
|
|
InspectionAttr,
|
|
):
|
|
"""A grouping of SQL expressions that are returned by a :class:`.Query`
|
|
under one namespace.
|
|
|
|
The :class:`.Bundle` essentially allows nesting of the tuple-based
|
|
results returned by a column-oriented :class:`_query.Query` object.
|
|
It also
|
|
is extensible via simple subclassing, where the primary capability
|
|
to override is that of how the set of expressions should be returned,
|
|
allowing post-processing as well as custom return types, without
|
|
involving ORM identity-mapped classes.
|
|
|
|
.. versionadded:: 0.9.0
|
|
|
|
.. seealso::
|
|
|
|
:ref:`bundles`
|
|
|
|
|
|
"""
|
|
|
|
single_entity = False
|
|
"""If True, queries for a single Bundle will be returned as a single
|
|
entity, rather than an element within a keyed tuple."""
|
|
|
|
is_clause_element = False
|
|
|
|
is_mapper = False
|
|
|
|
is_aliased_class = False
|
|
|
|
is_bundle = True
|
|
|
|
_propagate_attrs = util.immutabledict()
|
|
|
|
def __init__(self, name, *exprs, **kw):
|
|
r"""Construct a new :class:`.Bundle`.
|
|
|
|
e.g.::
|
|
|
|
bn = Bundle("mybundle", MyClass.x, MyClass.y)
|
|
|
|
for row in session.query(bn).filter(
|
|
bn.c.x == 5).filter(bn.c.y == 4):
|
|
print(row.mybundle.x, row.mybundle.y)
|
|
|
|
:param name: name of the bundle.
|
|
:param \*exprs: columns or SQL expressions comprising the bundle.
|
|
:param single_entity=False: if True, rows for this :class:`.Bundle`
|
|
can be returned as a "single entity" outside of any enclosing tuple
|
|
in the same manner as a mapped entity.
|
|
|
|
"""
|
|
self.name = self._label = name
|
|
self.exprs = exprs = [
|
|
coercions.expect(
|
|
roles.ColumnsClauseRole, expr, apply_propagate_attrs=self
|
|
)
|
|
for expr in exprs
|
|
]
|
|
|
|
self.c = self.columns = ColumnCollection(
|
|
(getattr(col, "key", col._label), col)
|
|
for col in [e._annotations.get("bundle", e) for e in exprs]
|
|
)
|
|
self.single_entity = kw.pop("single_entity", self.single_entity)
|
|
|
|
def _gen_cache_key(self, anon_map, bindparams):
|
|
return (self.__class__, self.name, self.single_entity) + tuple(
|
|
[expr._gen_cache_key(anon_map, bindparams) for expr in self.exprs]
|
|
)
|
|
|
|
@property
|
|
def mapper(self):
|
|
return self.exprs[0]._annotations.get("parentmapper", None)
|
|
|
|
@property
|
|
def entity(self):
|
|
return self.exprs[0]._annotations.get("parententity", None)
|
|
|
|
@property
|
|
def entity_namespace(self):
|
|
return self.c
|
|
|
|
columns = None
|
|
"""A namespace of SQL expressions referred to by this :class:`.Bundle`.
|
|
|
|
e.g.::
|
|
|
|
bn = Bundle("mybundle", MyClass.x, MyClass.y)
|
|
|
|
q = sess.query(bn).filter(bn.c.x == 5)
|
|
|
|
Nesting of bundles is also supported::
|
|
|
|
b1 = Bundle("b1",
|
|
Bundle('b2', MyClass.a, MyClass.b),
|
|
Bundle('b3', MyClass.x, MyClass.y)
|
|
)
|
|
|
|
q = sess.query(b1).filter(
|
|
b1.c.b2.c.a == 5).filter(b1.c.b3.c.y == 9)
|
|
|
|
.. seealso::
|
|
|
|
:attr:`.Bundle.c`
|
|
|
|
"""
|
|
|
|
c = None
|
|
"""An alias for :attr:`.Bundle.columns`."""
|
|
|
|
def _clone(self):
|
|
cloned = self.__class__.__new__(self.__class__)
|
|
cloned.__dict__.update(self.__dict__)
|
|
return cloned
|
|
|
|
def __clause_element__(self):
|
|
# ensure existing entity_namespace remains
|
|
annotations = {"bundle": self, "entity_namespace": self}
|
|
annotations.update(self._annotations)
|
|
|
|
plugin_subject = self.exprs[0]._propagate_attrs.get(
|
|
"plugin_subject", self.entity
|
|
)
|
|
return (
|
|
expression.ClauseList(
|
|
_literal_as_text_role=roles.ColumnsClauseRole,
|
|
group=False,
|
|
*[e._annotations.get("bundle", e) for e in self.exprs]
|
|
)
|
|
._annotate(annotations)
|
|
._set_propagate_attrs(
|
|
# the Bundle *must* use the orm plugin no matter what. the
|
|
# subject can be None but it's much better if it's not.
|
|
{
|
|
"compile_state_plugin": "orm",
|
|
"plugin_subject": plugin_subject,
|
|
}
|
|
)
|
|
)
|
|
|
|
@property
|
|
def clauses(self):
|
|
return self.__clause_element__().clauses
|
|
|
|
def label(self, name):
|
|
"""Provide a copy of this :class:`.Bundle` passing a new label."""
|
|
|
|
cloned = self._clone()
|
|
cloned.name = name
|
|
return cloned
|
|
|
|
def create_row_processor(self, query, procs, labels):
|
|
"""Produce the "row processing" function for this :class:`.Bundle`.
|
|
|
|
May be overridden by subclasses.
|
|
|
|
.. seealso::
|
|
|
|
:ref:`bundles` - includes an example of subclassing.
|
|
|
|
"""
|
|
keyed_tuple = result_tuple(labels, [() for l in labels])
|
|
|
|
def proc(row):
|
|
return keyed_tuple([proc(row) for proc in procs])
|
|
|
|
return proc
|
|
|
|
|
|
def _orm_annotate(element, exclude=None):
|
|
"""Deep copy the given ClauseElement, annotating each element with the
|
|
"_orm_adapt" flag.
|
|
|
|
Elements within the exclude collection will be cloned but not annotated.
|
|
|
|
"""
|
|
return sql_util._deep_annotate(element, {"_orm_adapt": True}, exclude)
|
|
|
|
|
|
def _orm_deannotate(element):
|
|
"""Remove annotations that link a column to a particular mapping.
|
|
|
|
Note this doesn't affect "remote" and "foreign" annotations
|
|
passed by the :func:`_orm.foreign` and :func:`_orm.remote`
|
|
annotators.
|
|
|
|
"""
|
|
|
|
return sql_util._deep_deannotate(
|
|
element, values=("_orm_adapt", "parententity")
|
|
)
|
|
|
|
|
|
def _orm_full_deannotate(element):
|
|
return sql_util._deep_deannotate(element)
|
|
|
|
|
|
class _ORMJoin(expression.Join):
|
|
"""Extend Join to support ORM constructs as input."""
|
|
|
|
__visit_name__ = expression.Join.__visit_name__
|
|
|
|
inherit_cache = True
|
|
|
|
def __init__(
|
|
self,
|
|
left,
|
|
right,
|
|
onclause=None,
|
|
isouter=False,
|
|
full=False,
|
|
_left_memo=None,
|
|
_right_memo=None,
|
|
_extra_criteria=(),
|
|
):
|
|
left_info = inspection.inspect(left)
|
|
|
|
right_info = inspection.inspect(right)
|
|
adapt_to = right_info.selectable
|
|
|
|
# used by joined eager loader
|
|
self._left_memo = _left_memo
|
|
self._right_memo = _right_memo
|
|
|
|
# legacy, for string attr name ON clause. if that's removed
|
|
# then the "_joined_from_info" concept can go
|
|
left_orm_info = getattr(left, "_joined_from_info", left_info)
|
|
self._joined_from_info = right_info
|
|
if isinstance(onclause, util.string_types):
|
|
onclause = getattr(left_orm_info.entity, onclause)
|
|
# ####
|
|
|
|
if isinstance(onclause, attributes.QueryableAttribute):
|
|
on_selectable = onclause.comparator._source_selectable()
|
|
prop = onclause.property
|
|
_extra_criteria += onclause._extra_criteria
|
|
elif isinstance(onclause, MapperProperty):
|
|
# used internally by joined eager loader...possibly not ideal
|
|
prop = onclause
|
|
on_selectable = prop.parent.selectable
|
|
else:
|
|
prop = None
|
|
|
|
if prop:
|
|
left_selectable = left_info.selectable
|
|
|
|
if sql_util.clause_is_present(on_selectable, left_selectable):
|
|
adapt_from = on_selectable
|
|
else:
|
|
adapt_from = left_selectable
|
|
|
|
(
|
|
pj,
|
|
sj,
|
|
source,
|
|
dest,
|
|
secondary,
|
|
target_adapter,
|
|
) = prop._create_joins(
|
|
source_selectable=adapt_from,
|
|
dest_selectable=adapt_to,
|
|
source_polymorphic=True,
|
|
of_type_entity=right_info,
|
|
alias_secondary=True,
|
|
extra_criteria=_extra_criteria,
|
|
)
|
|
|
|
if sj is not None:
|
|
if isouter:
|
|
# note this is an inner join from secondary->right
|
|
right = sql.join(secondary, right, sj)
|
|
onclause = pj
|
|
else:
|
|
left = sql.join(left, secondary, pj, isouter)
|
|
onclause = sj
|
|
else:
|
|
onclause = pj
|
|
|
|
self._target_adapter = target_adapter
|
|
|
|
augment_onclause = onclause is None and _extra_criteria
|
|
expression.Join.__init__(self, left, right, onclause, isouter, full)
|
|
|
|
if augment_onclause:
|
|
self.onclause &= sql.and_(*_extra_criteria)
|
|
|
|
if (
|
|
not prop
|
|
and getattr(right_info, "mapper", None)
|
|
and right_info.mapper.single
|
|
):
|
|
# if single inheritance target and we are using a manual
|
|
# or implicit ON clause, augment it the same way we'd augment the
|
|
# WHERE.
|
|
single_crit = right_info.mapper._single_table_criterion
|
|
if single_crit is not None:
|
|
if right_info.is_aliased_class:
|
|
single_crit = right_info._adapter.traverse(single_crit)
|
|
self.onclause = self.onclause & single_crit
|
|
|
|
def _splice_into_center(self, other):
|
|
"""Splice a join into the center.
|
|
|
|
Given join(a, b) and join(b, c), return join(a, b).join(c)
|
|
|
|
"""
|
|
leftmost = other
|
|
while isinstance(leftmost, sql.Join):
|
|
leftmost = leftmost.left
|
|
|
|
assert self.right is leftmost
|
|
|
|
left = _ORMJoin(
|
|
self.left,
|
|
other.left,
|
|
self.onclause,
|
|
isouter=self.isouter,
|
|
_left_memo=self._left_memo,
|
|
_right_memo=other._left_memo,
|
|
)
|
|
|
|
return _ORMJoin(
|
|
left,
|
|
other.right,
|
|
other.onclause,
|
|
isouter=other.isouter,
|
|
_right_memo=other._right_memo,
|
|
)
|
|
|
|
def join(
|
|
self,
|
|
right,
|
|
onclause=None,
|
|
isouter=False,
|
|
full=False,
|
|
join_to_left=None,
|
|
):
|
|
return _ORMJoin(self, right, onclause, full=full, isouter=isouter)
|
|
|
|
def outerjoin(self, right, onclause=None, full=False, join_to_left=None):
|
|
return _ORMJoin(self, right, onclause, isouter=True, full=full)
|
|
|
|
|
|
def join(
|
|
left, right, onclause=None, isouter=False, full=False, join_to_left=None
|
|
):
|
|
r"""Produce an inner join between left and right clauses.
|
|
|
|
:func:`_orm.join` is an extension to the core join interface
|
|
provided by :func:`_expression.join()`, where the
|
|
left and right selectables may be not only core selectable
|
|
objects such as :class:`_schema.Table`, but also mapped classes or
|
|
:class:`.AliasedClass` instances. The "on" clause can
|
|
be a SQL expression or an ORM mapped attribute
|
|
referencing a configured :func:`_orm.relationship`.
|
|
|
|
.. deprecated:: 1.4 using a string relationship name for the "onclause"
|
|
is deprecated and will be removed in 2.0; the onclause may be only
|
|
an ORM-mapped relationship attribute or a SQL expression construct.
|
|
|
|
:func:`_orm.join` is not commonly needed in modern usage,
|
|
as its functionality is encapsulated within that of the
|
|
:meth:`_sql.Select.join` and :meth:`_query.Query.join`
|
|
methods. which feature a
|
|
significant amount of automation beyond :func:`_orm.join`
|
|
by itself. Explicit use of :func:`_orm.join`
|
|
with ORM-enabled SELECT statements involves use of the
|
|
:meth:`_sql.Select.select_from` method, as in::
|
|
|
|
from sqlalchemy.orm import join
|
|
stmt = select(User).\
|
|
select_from(join(User, Address, User.addresses)).\
|
|
filter(Address.email_address=='foo@bar.com')
|
|
|
|
In modern SQLAlchemy the above join can be written more
|
|
succinctly as::
|
|
|
|
stmt = select(User).\
|
|
join(User.addresses).\
|
|
filter(Address.email_address=='foo@bar.com')
|
|
|
|
See :ref:`orm_queryguide_joins` for information on modern usage
|
|
of ORM level joins.
|
|
|
|
.. deprecated:: 0.8
|
|
|
|
the ``join_to_left`` parameter is deprecated, and will be removed
|
|
in a future release. The parameter has no effect.
|
|
|
|
"""
|
|
return _ORMJoin(left, right, onclause, isouter, full)
|
|
|
|
|
|
def outerjoin(left, right, onclause=None, full=False, join_to_left=None):
|
|
"""Produce a left outer join between left and right clauses.
|
|
|
|
This is the "outer join" version of the :func:`_orm.join` function,
|
|
featuring the same behavior except that an OUTER JOIN is generated.
|
|
See that function's documentation for other usage details.
|
|
|
|
"""
|
|
return _ORMJoin(left, right, onclause, True, full)
|
|
|
|
|
|
def with_parent(instance, prop, from_entity=None):
|
|
"""Create filtering criterion that relates this query's primary entity
|
|
to the given related instance, using established
|
|
:func:`_orm.relationship()`
|
|
configuration.
|
|
|
|
E.g.::
|
|
|
|
stmt = select(Address).where(with_parent(some_user, User.addresses))
|
|
|
|
|
|
The SQL rendered is the same as that rendered when a lazy loader
|
|
would fire off from the given parent on that attribute, meaning
|
|
that the appropriate state is taken from the parent object in
|
|
Python without the need to render joins to the parent table
|
|
in the rendered statement.
|
|
|
|
The given property may also make use of :meth:`_orm.PropComparator.of_type`
|
|
to indicate the left side of the criteria::
|
|
|
|
|
|
a1 = aliased(Address)
|
|
a2 = aliased(Address)
|
|
stmt = select(a1, a2).where(
|
|
with_parent(u1, User.addresses.of_type(a2))
|
|
)
|
|
|
|
The above use is equivalent to using the
|
|
:func:`_orm.with_parent.from_entity` argument::
|
|
|
|
a1 = aliased(Address)
|
|
a2 = aliased(Address)
|
|
stmt = select(a1, a2).where(
|
|
with_parent(u1, User.addresses, from_entity=a2)
|
|
)
|
|
|
|
:param instance:
|
|
An instance which has some :func:`_orm.relationship`.
|
|
|
|
:param property:
|
|
String property name, or class-bound attribute, which indicates
|
|
what relationship from the instance should be used to reconcile the
|
|
parent/child relationship.
|
|
|
|
.. deprecated:: 1.4 Using strings is deprecated and will be removed
|
|
in SQLAlchemy 2.0. Please use the class-bound attribute directly.
|
|
|
|
:param from_entity:
|
|
Entity in which to consider as the left side. This defaults to the
|
|
"zero" entity of the :class:`_query.Query` itself.
|
|
|
|
.. versionadded:: 1.2
|
|
|
|
"""
|
|
if isinstance(prop, util.string_types):
|
|
util.warn_deprecated_20(
|
|
"Using strings to indicate relationship names in the ORM "
|
|
"with_parent() function is deprecated and will be removed "
|
|
"SQLAlchemy 2.0. Please use the class-bound attribute directly."
|
|
)
|
|
mapper = object_mapper(instance)
|
|
prop = getattr(mapper.class_, prop).property
|
|
elif isinstance(prop, attributes.QueryableAttribute):
|
|
if prop._of_type:
|
|
from_entity = prop._of_type
|
|
prop = prop.property
|
|
|
|
return prop._with_parent(instance, from_entity=from_entity)
|
|
|
|
|
|
def has_identity(object_):
|
|
"""Return True if the given object has a database
|
|
identity.
|
|
|
|
This typically corresponds to the object being
|
|
in either the persistent or detached state.
|
|
|
|
.. seealso::
|
|
|
|
:func:`.was_deleted`
|
|
|
|
"""
|
|
state = attributes.instance_state(object_)
|
|
return state.has_identity
|
|
|
|
|
|
def was_deleted(object_):
|
|
"""Return True if the given object was deleted
|
|
within a session flush.
|
|
|
|
This is regardless of whether or not the object is
|
|
persistent or detached.
|
|
|
|
.. seealso::
|
|
|
|
:attr:`.InstanceState.was_deleted`
|
|
|
|
"""
|
|
|
|
state = attributes.instance_state(object_)
|
|
return state.was_deleted
|
|
|
|
|
|
def _entity_corresponds_to(given, entity):
|
|
"""determine if 'given' corresponds to 'entity', in terms
|
|
of an entity passed to Query that would match the same entity
|
|
being referred to elsewhere in the query.
|
|
|
|
"""
|
|
if entity.is_aliased_class:
|
|
if given.is_aliased_class:
|
|
if entity._base_alias() is given._base_alias():
|
|
return True
|
|
return False
|
|
elif given.is_aliased_class:
|
|
if given._use_mapper_path:
|
|
return entity in given.with_polymorphic_mappers
|
|
else:
|
|
return entity is given
|
|
|
|
return entity.common_parent(given)
|
|
|
|
|
|
def _entity_corresponds_to_use_path_impl(given, entity):
|
|
"""determine if 'given' corresponds to 'entity', in terms
|
|
of a path of loader options where a mapped attribute is taken to
|
|
be a member of a parent entity.
|
|
|
|
e.g.::
|
|
|
|
someoption(A).someoption(A.b) # -> fn(A, A) -> True
|
|
someoption(A).someoption(C.d) # -> fn(A, C) -> False
|
|
|
|
a1 = aliased(A)
|
|
someoption(a1).someoption(A.b) # -> fn(a1, A) -> False
|
|
someoption(a1).someoption(a1.b) # -> fn(a1, a1) -> True
|
|
|
|
wp = with_polymorphic(A, [A1, A2])
|
|
someoption(wp).someoption(A1.foo) # -> fn(wp, A1) -> False
|
|
someoption(wp).someoption(wp.A1.foo) # -> fn(wp, wp.A1) -> True
|
|
|
|
|
|
"""
|
|
if given.is_aliased_class:
|
|
return (
|
|
entity.is_aliased_class
|
|
and not entity._use_mapper_path
|
|
and (given is entity or given in entity._with_polymorphic_entities)
|
|
)
|
|
elif not entity.is_aliased_class:
|
|
return given.common_parent(entity.mapper)
|
|
else:
|
|
return (
|
|
entity._use_mapper_path
|
|
and given in entity.with_polymorphic_mappers
|
|
)
|
|
|
|
|
|
def _entity_isa(given, mapper):
|
|
"""determine if 'given' "is a" mapper, in terms of the given
|
|
would load rows of type 'mapper'.
|
|
|
|
"""
|
|
if given.is_aliased_class:
|
|
return mapper in given.with_polymorphic_mappers or given.mapper.isa(
|
|
mapper
|
|
)
|
|
elif given.with_polymorphic_mappers:
|
|
return mapper in given.with_polymorphic_mappers
|
|
else:
|
|
return given.isa(mapper)
|
|
|
|
|
|
def randomize_unitofwork():
|
|
"""Use random-ordering sets within the unit of work in order
|
|
to detect unit of work sorting issues.
|
|
|
|
This is a utility function that can be used to help reproduce
|
|
inconsistent unit of work sorting issues. For example,
|
|
if two kinds of objects A and B are being inserted, and
|
|
B has a foreign key reference to A - the A must be inserted first.
|
|
However, if there is no relationship between A and B, the unit of work
|
|
won't know to perform this sorting, and an operation may or may not
|
|
fail, depending on how the ordering works out. Since Python sets
|
|
and dictionaries have non-deterministic ordering, such an issue may
|
|
occur on some runs and not on others, and in practice it tends to
|
|
have a great dependence on the state of the interpreter. This leads
|
|
to so-called "heisenbugs" where changing entirely irrelevant aspects
|
|
of the test program still cause the failure behavior to change.
|
|
|
|
By calling ``randomize_unitofwork()`` when a script first runs, the
|
|
ordering of a key series of sets within the unit of work implementation
|
|
are randomized, so that the script can be minimized down to the
|
|
fundamental mapping and operation that's failing, while still reproducing
|
|
the issue on at least some runs.
|
|
|
|
This utility is also available when running the test suite via the
|
|
``--reversetop`` flag.
|
|
|
|
"""
|
|
from sqlalchemy.orm import unitofwork, session, mapper, dependency
|
|
from sqlalchemy.util import topological
|
|
from sqlalchemy.testing.util import RandomSet
|
|
|
|
topological.set = (
|
|
unitofwork.set
|
|
) = session.set = mapper.set = dependency.set = RandomSet
|
|
|
|
|
|
def _getitem(iterable_query, item, allow_negative):
|
|
"""calculate __getitem__ in terms of an iterable query object
|
|
that also has a slice() method.
|
|
|
|
"""
|
|
|
|
def _no_negative_indexes():
|
|
if not allow_negative:
|
|
raise IndexError(
|
|
"negative indexes are not accepted by SQL "
|
|
"index / slice operators"
|
|
)
|
|
else:
|
|
util.warn_deprecated_20(
|
|
"Support for negative indexes for SQL index / slice operators "
|
|
"will be "
|
|
"removed in 2.0; these operators fetch the complete result "
|
|
"and do not work efficiently."
|
|
)
|
|
|
|
if isinstance(item, slice):
|
|
start, stop, step = util.decode_slice(item)
|
|
|
|
if (
|
|
isinstance(stop, int)
|
|
and isinstance(start, int)
|
|
and stop - start <= 0
|
|
):
|
|
return []
|
|
|
|
elif (isinstance(start, int) and start < 0) or (
|
|
isinstance(stop, int) and stop < 0
|
|
):
|
|
_no_negative_indexes()
|
|
return list(iterable_query)[item]
|
|
|
|
res = iterable_query.slice(start, stop)
|
|
if step is not None:
|
|
return list(res)[None : None : item.step]
|
|
else:
|
|
return list(res)
|
|
else:
|
|
if item == -1:
|
|
_no_negative_indexes()
|
|
return list(iterable_query)[-1]
|
|
else:
|
|
return list(iterable_query[item : item + 1])[0]
|