OpenHome/venv/Lib/site-packages/sqlalchemy/orm/loading.py
2021-07-21 21:33:05 +02:00

1464 lines
48 KiB
Python

# orm/loading.py
# Copyright (C) 2005-2021 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""private module containing functions used to convert database
rows into object instances and associated state.
the functions here are called primarily by Query, Mapper,
as well as some of the attribute loading strategies.
"""
from __future__ import absolute_import
from . import attributes
from . import exc as orm_exc
from . import path_registry
from . import strategy_options
from .base import _DEFER_FOR_STATE
from .base import _RAISE_FOR_STATE
from .base import _SET_DEFERRED_EXPIRED
from .util import _none_set
from .util import state_str
from .. import exc as sa_exc
from .. import future
from .. import util
from ..engine import result_tuple
from ..engine.result import ChunkedIteratorResult
from ..engine.result import FrozenResult
from ..engine.result import SimpleResultMetaData
from ..sql import util as sql_util
from ..sql.selectable import LABEL_STYLE_TABLENAME_PLUS_COL
_new_runid = util.counter()
def instances(cursor, context):
"""Return a :class:`.Result` given an ORM query context.
:param cursor: a :class:`.CursorResult`, generated by a statement
which came from :class:`.ORMCompileState`
:param context: a :class:`.QueryContext` object
:return: a :class:`.Result` object representing ORM results
.. versionchanged:: 1.4 The instances() function now uses
:class:`.Result` objects and has an all new interface.
"""
context.runid = _new_runid()
context.post_load_paths = {}
compile_state = context.compile_state
filtered = compile_state._has_mapper_entities
single_entity = (
not context.load_options._only_return_tuples
and len(compile_state._entities) == 1
and compile_state._entities[0].supports_single_entity
)
try:
(process, labels, extra) = list(
zip(
*[
query_entity.row_processor(context, cursor)
for query_entity in context.compile_state._entities
]
)
)
if context.yield_per and (
context.loaders_require_buffering
or context.loaders_require_uniquing
):
raise sa_exc.InvalidRequestError(
"Can't use yield_per with eager loaders that require uniquing "
"or row buffering, e.g. joinedload() against collections "
"or subqueryload(). Consider the selectinload() strategy "
"for better flexibility in loading objects."
)
except Exception:
with util.safe_reraise():
cursor.close()
def _no_unique(entry):
raise sa_exc.InvalidRequestError(
"Can't use the ORM yield_per feature in conjunction with unique()"
)
row_metadata = SimpleResultMetaData(
labels,
extra,
_unique_filters=[
_no_unique
if context.yield_per
else id
if ent.use_id_for_hash
else None
for ent in context.compile_state._entities
],
)
def chunks(size):
while True:
yield_per = size
context.partials = {}
if yield_per:
fetch = cursor.fetchmany(yield_per)
if not fetch:
break
else:
fetch = cursor._raw_all_rows()
if single_entity:
proc = process[0]
rows = [proc(row) for row in fetch]
else:
rows = [
tuple([proc(row) for proc in process]) for row in fetch
]
for path, post_load in context.post_load_paths.items():
post_load.invoke(context, path)
yield rows
if not yield_per:
break
if context.execution_options.get("prebuffer_rows", False):
# this is a bit of a hack at the moment.
# I would rather have some option in the result to pre-buffer
# internally.
_prebuffered = list(chunks(None))
def chunks(size):
return iter(_prebuffered)
result = ChunkedIteratorResult(
row_metadata,
chunks,
source_supports_scalars=single_entity,
raw=cursor,
dynamic_yield_per=cursor.context._is_server_side,
)
# filtered and single_entity are used to indicate to legacy Query that the
# query has ORM entities, so legacy deduping and scalars should be called
# on the result.
result._attributes = result._attributes.union(
dict(filtered=filtered, is_single_entity=single_entity)
)
# multi_row_eager_loaders OTOH is specific to joinedload.
if context.compile_state.multi_row_eager_loaders:
def require_unique(obj):
raise sa_exc.InvalidRequestError(
"The unique() method must be invoked on this Result, "
"as it contains results that include joined eager loads "
"against collections"
)
result._unique_filter_state = (None, require_unique)
if context.yield_per:
result.yield_per(context.yield_per)
return result
@util.preload_module("sqlalchemy.orm.context")
def merge_frozen_result(session, statement, frozen_result, load=True):
"""Merge a :class:`_engine.FrozenResult` back into a :class:`_orm.Session`,
returning a new :class:`_engine.Result` object with :term:`persistent`
objects.
See the section :ref:`do_orm_execute_re_executing` for an example.
.. seealso::
:ref:`do_orm_execute_re_executing`
:meth:`_engine.Result.freeze`
:class:`_engine.FrozenResult`
"""
querycontext = util.preloaded.orm_context
if load:
# flush current contents if we expect to load data
session._autoflush()
ctx = querycontext.ORMSelectCompileState._create_entities_collection(
statement, legacy=False
)
autoflush = session.autoflush
try:
session.autoflush = False
mapped_entities = [
i
for i, e in enumerate(ctx._entities)
if isinstance(e, querycontext._MapperEntity)
]
keys = [ent._label_name for ent in ctx._entities]
keyed_tuple = result_tuple(
keys, [ent._extra_entities for ent in ctx._entities]
)
result = []
for newrow in frozen_result.rewrite_rows():
for i in mapped_entities:
if newrow[i] is not None:
newrow[i] = session._merge(
attributes.instance_state(newrow[i]),
attributes.instance_dict(newrow[i]),
load=load,
_recursive={},
_resolve_conflict_map={},
)
result.append(keyed_tuple(newrow))
return frozen_result.with_new_rows(result)
finally:
session.autoflush = autoflush
@util.deprecated(
"2.0",
"The :func:`_orm.merge_result` method is superseded by the "
":func:`_orm.merge_frozen_result` function.",
)
@util.preload_module("sqlalchemy.orm.context")
def merge_result(query, iterator, load=True):
"""Merge a result into this :class:`.Query` object's Session."""
querycontext = util.preloaded.orm_context
session = query.session
if load:
# flush current contents if we expect to load data
session._autoflush()
# TODO: need test coverage and documentation for the FrozenResult
# use case.
if isinstance(iterator, FrozenResult):
frozen_result = iterator
iterator = iter(frozen_result.data)
else:
frozen_result = None
ctx = querycontext.ORMSelectCompileState._create_entities_collection(
query, legacy=True
)
autoflush = session.autoflush
try:
session.autoflush = False
single_entity = not frozen_result and len(ctx._entities) == 1
if single_entity:
if isinstance(ctx._entities[0], querycontext._MapperEntity):
result = [
session._merge(
attributes.instance_state(instance),
attributes.instance_dict(instance),
load=load,
_recursive={},
_resolve_conflict_map={},
)
for instance in iterator
]
else:
result = list(iterator)
else:
mapped_entities = [
i
for i, e in enumerate(ctx._entities)
if isinstance(e, querycontext._MapperEntity)
]
result = []
keys = [ent._label_name for ent in ctx._entities]
keyed_tuple = result_tuple(
keys, [ent._extra_entities for ent in ctx._entities]
)
for row in iterator:
newrow = list(row)
for i in mapped_entities:
if newrow[i] is not None:
newrow[i] = session._merge(
attributes.instance_state(newrow[i]),
attributes.instance_dict(newrow[i]),
load=load,
_recursive={},
_resolve_conflict_map={},
)
result.append(keyed_tuple(newrow))
if frozen_result:
return frozen_result.with_data(result)
else:
return iter(result)
finally:
session.autoflush = autoflush
def get_from_identity(session, mapper, key, passive):
"""Look up the given key in the given session's identity map,
check the object for expired state if found.
"""
instance = session.identity_map.get(key)
if instance is not None:
state = attributes.instance_state(instance)
if mapper.inherits and not state.mapper.isa(mapper):
return attributes.PASSIVE_CLASS_MISMATCH
# expired - ensure it still exists
if state.expired:
if not passive & attributes.SQL_OK:
# TODO: no coverage here
return attributes.PASSIVE_NO_RESULT
elif not passive & attributes.RELATED_OBJECT_OK:
# this mode is used within a flush and the instance's
# expired state will be checked soon enough, if necessary.
# also used by immediateloader for a mutually-dependent
# o2m->m2m load, :ticket:`6301`
return instance
try:
state._load_expired(state, passive)
except orm_exc.ObjectDeletedError:
session._remove_newly_deleted([state])
return None
return instance
else:
return None
def load_on_ident(
session,
statement,
key,
load_options=None,
refresh_state=None,
with_for_update=None,
only_load_props=None,
no_autoflush=False,
bind_arguments=util.EMPTY_DICT,
execution_options=util.EMPTY_DICT,
):
"""Load the given identity key from the database."""
if key is not None:
ident = key[1]
identity_token = key[2]
else:
ident = identity_token = None
return load_on_pk_identity(
session,
statement,
ident,
load_options=load_options,
refresh_state=refresh_state,
with_for_update=with_for_update,
only_load_props=only_load_props,
identity_token=identity_token,
no_autoflush=no_autoflush,
bind_arguments=bind_arguments,
execution_options=execution_options,
)
def load_on_pk_identity(
session,
statement,
primary_key_identity,
load_options=None,
refresh_state=None,
with_for_update=None,
only_load_props=None,
identity_token=None,
no_autoflush=False,
bind_arguments=util.EMPTY_DICT,
execution_options=util.EMPTY_DICT,
):
"""Load the given primary key identity from the database."""
query = statement
q = query._clone()
is_lambda = q._is_lambda_element
# TODO: fix these imports ....
from .context import QueryContext, ORMCompileState
if load_options is None:
load_options = QueryContext.default_load_options
compile_options = ORMCompileState.default_compile_options
if primary_key_identity is not None:
mapper = query._propagate_attrs["plugin_subject"]
(_get_clause, _get_params) = mapper._get_clause
# None present in ident - turn those comparisons
# into "IS NULL"
if None in primary_key_identity:
nones = set(
[
_get_params[col].key
for col, value in zip(
mapper.primary_key, primary_key_identity
)
if value is None
]
)
_get_clause = sql_util.adapt_criterion_to_null(_get_clause, nones)
if len(nones) == len(primary_key_identity):
util.warn(
"fully NULL primary key identity cannot load any "
"object. This condition may raise an error in a future "
"release."
)
if is_lambda:
q = q.add_criteria(
lambda q: q.where(
sql_util._deep_annotate(_get_clause, {"_orm_adapt": True})
),
# this track_on will allow the lambda to refresh if
# _get_clause goes stale due to reconfigured mapper.
# however, it's not needed as the lambda otherwise tracks
# on the SQL cache key of the expression. the main thing
# is that the bindparam.key stays the same if the cache key
# stays the same, as we are referring to the .key explicitly
# in the params.
# track_on=[id(_get_clause)]
)
else:
q._where_criteria = (
sql_util._deep_annotate(_get_clause, {"_orm_adapt": True}),
)
params = dict(
[
(_get_params[primary_key].key, id_val)
for id_val, primary_key in zip(
primary_key_identity, mapper.primary_key
)
]
)
else:
params = None
if is_lambda:
if with_for_update is not None or refresh_state or only_load_props:
raise NotImplementedError(
"refresh operation not supported with lambda statement"
)
version_check = False
_, load_options = _set_get_options(
compile_options,
load_options,
version_check=version_check,
only_load_props=only_load_props,
refresh_state=refresh_state,
identity_token=identity_token,
)
if no_autoflush:
load_options += {"_autoflush": False}
else:
if with_for_update is not None:
version_check = True
q._for_update_arg = with_for_update
elif query._for_update_arg is not None:
version_check = True
q._for_update_arg = query._for_update_arg
else:
version_check = False
if refresh_state and refresh_state.load_options:
compile_options += {
"_current_path": refresh_state.load_path.parent
}
q = q.options(*refresh_state.load_options)
# TODO: most of the compile_options that are not legacy only involve
# this function, so try to see if handling of them can mostly be local
# to here
q._compile_options, load_options = _set_get_options(
compile_options,
load_options,
version_check=version_check,
only_load_props=only_load_props,
refresh_state=refresh_state,
identity_token=identity_token,
)
q._order_by = None
if no_autoflush:
load_options += {"_autoflush": False}
execution_options = util.EMPTY_DICT.merge_with(
execution_options, {"_sa_orm_load_options": load_options}
)
result = (
session.execute(
q,
params=params,
execution_options=execution_options,
bind_arguments=bind_arguments,
)
.unique()
.scalars()
)
try:
return result.one()
except orm_exc.NoResultFound:
return None
def _set_get_options(
compile_opt,
load_opt,
populate_existing=None,
version_check=None,
only_load_props=None,
refresh_state=None,
identity_token=None,
):
compile_options = {}
load_options = {}
if version_check:
load_options["_version_check"] = version_check
if populate_existing:
load_options["_populate_existing"] = populate_existing
if refresh_state:
load_options["_refresh_state"] = refresh_state
compile_options["_for_refresh_state"] = True
if only_load_props:
compile_options["_only_load_props"] = frozenset(only_load_props)
if identity_token:
load_options["_refresh_identity_token"] = identity_token
if load_options:
load_opt += load_options
if compile_options:
compile_opt += compile_options
return compile_opt, load_opt
def _setup_entity_query(
compile_state,
mapper,
query_entity,
path,
adapter,
column_collection,
with_polymorphic=None,
only_load_props=None,
polymorphic_discriminator=None,
**kw
):
if with_polymorphic:
poly_properties = mapper._iterate_polymorphic_properties(
with_polymorphic
)
else:
poly_properties = mapper._polymorphic_properties
quick_populators = {}
path.set(compile_state.attributes, "memoized_setups", quick_populators)
# for the lead entities in the path, e.g. not eager loads, and
# assuming a user-passed aliased class, e.g. not a from_self() or any
# implicit aliasing, don't add columns to the SELECT that aren't
# in the thing that's aliased.
check_for_adapt = adapter and len(path) == 1 and path[-1].is_aliased_class
for value in poly_properties:
if only_load_props and value.key not in only_load_props:
continue
value.setup(
compile_state,
query_entity,
path,
adapter,
only_load_props=only_load_props,
column_collection=column_collection,
memoized_populators=quick_populators,
check_for_adapt=check_for_adapt,
**kw
)
if (
polymorphic_discriminator is not None
and polymorphic_discriminator is not mapper.polymorphic_on
):
if adapter:
pd = adapter.columns[polymorphic_discriminator]
else:
pd = polymorphic_discriminator
column_collection.append(pd)
def _warn_for_runid_changed(state):
util.warn(
"Loading context for %s has changed within a load/refresh "
"handler, suggesting a row refresh operation took place. If this "
"event handler is expected to be "
"emitting row refresh operations within an existing load or refresh "
"operation, set restore_load_context=True when establishing the "
"listener to ensure the context remains unchanged when the event "
"handler completes." % (state_str(state),)
)
def _instance_processor(
query_entity,
mapper,
context,
result,
path,
adapter,
only_load_props=None,
refresh_state=None,
polymorphic_discriminator=None,
_polymorphic_from=None,
):
"""Produce a mapper level row processor callable
which processes rows into mapped instances."""
# note that this method, most of which exists in a closure
# called _instance(), resists being broken out, as
# attempts to do so tend to add significant function
# call overhead. _instance() is the most
# performance-critical section in the whole ORM.
identity_class = mapper._identity_class
compile_state = context.compile_state
# look for "row getter" functions that have been assigned along
# with the compile state that were cached from a previous load.
# these are operator.itemgetter() objects that each will extract a
# particular column from each row.
getter_key = ("getters", mapper)
getters = path.get(compile_state.attributes, getter_key, None)
if getters is None:
# no getters, so go through a list of attributes we are loading for,
# and the ones that are column based will have already put information
# for us in another collection "memoized_setups", which represents the
# output of the LoaderStrategy.setup_query() method. We can just as
# easily call LoaderStrategy.create_row_processor for each, but by
# getting it all at once from setup_query we save another method call
# per attribute.
props = mapper._prop_set
if only_load_props is not None:
props = props.intersection(
mapper._props[k] for k in only_load_props
)
quick_populators = path.get(
context.attributes, "memoized_setups", _none_set
)
todo = []
cached_populators = {
"new": [],
"quick": [],
"deferred": [],
"expire": [],
"delayed": [],
"existing": [],
"eager": [],
}
if refresh_state is None:
# we can also get the "primary key" tuple getter function
pk_cols = mapper.primary_key
if adapter:
pk_cols = [adapter.columns[c] for c in pk_cols]
primary_key_getter = result._tuple_getter(pk_cols)
else:
primary_key_getter = None
getters = {
"cached_populators": cached_populators,
"todo": todo,
"primary_key_getter": primary_key_getter,
}
for prop in props:
if prop in quick_populators:
# this is an inlined path just for column-based attributes.
col = quick_populators[prop]
if col is _DEFER_FOR_STATE:
cached_populators["new"].append(
(prop.key, prop._deferred_column_loader)
)
elif col is _SET_DEFERRED_EXPIRED:
# note that in this path, we are no longer
# searching in the result to see if the column might
# be present in some unexpected way.
cached_populators["expire"].append((prop.key, False))
elif col is _RAISE_FOR_STATE:
cached_populators["new"].append(
(prop.key, prop._raise_column_loader)
)
else:
getter = None
if adapter:
# this logic had been removed for all 1.4 releases
# up until 1.4.18; the adapter here is particularly
# the compound eager adapter which isn't accommodated
# in the quick_populators right now. The "fallback"
# logic below instead took over in many more cases
# until issue #6596 was identified.
# note there is still an issue where this codepath
# produces no "getter" for cases where a joined-inh
# mapping includes a labeled column property, meaning
# KeyError is caught internally and we fall back to
# _getter(col), which works anyway. The adapter
# here for joined inh without any aliasing might not
# be useful. Tests which see this include
# test.orm.inheritance.test_basic ->
# EagerTargetingTest.test_adapt_stringency
# OptimizedLoadTest.test_column_expression_joined
# PolymorphicOnNotLocalTest.test_polymorphic_on_column_prop # noqa E501
#
adapted_col = adapter.columns[col]
if adapted_col is not None:
getter = result._getter(adapted_col, False)
if not getter:
getter = result._getter(col, False)
if getter:
cached_populators["quick"].append((prop.key, getter))
else:
# fall back to the ColumnProperty itself, which
# will iterate through all of its columns
# to see if one fits
prop.create_row_processor(
context,
query_entity,
path,
mapper,
result,
adapter,
cached_populators,
)
else:
# loader strategies like subqueryload, selectinload,
# joinedload, basically relationships, these need to interact
# with the context each time to work correctly.
todo.append(prop)
path.set(compile_state.attributes, getter_key, getters)
cached_populators = getters["cached_populators"]
populators = {key: list(value) for key, value in cached_populators.items()}
for prop in getters["todo"]:
prop.create_row_processor(
context, query_entity, path, mapper, result, adapter, populators
)
propagated_loader_options = context.propagated_loader_options
load_path = (
context.compile_state.current_path + path
if context.compile_state.current_path.path
else path
)
session_identity_map = context.session.identity_map
populate_existing = context.populate_existing or mapper.always_refresh
load_evt = bool(mapper.class_manager.dispatch.load)
refresh_evt = bool(mapper.class_manager.dispatch.refresh)
persistent_evt = bool(context.session.dispatch.loaded_as_persistent)
if persistent_evt:
loaded_as_persistent = context.session.dispatch.loaded_as_persistent
instance_state = attributes.instance_state
instance_dict = attributes.instance_dict
session_id = context.session.hash_key
runid = context.runid
identity_token = context.identity_token
version_check = context.version_check
if version_check:
version_id_col = mapper.version_id_col
if version_id_col is not None:
if adapter:
version_id_col = adapter.columns[version_id_col]
version_id_getter = result._getter(version_id_col)
else:
version_id_getter = None
if not refresh_state and _polymorphic_from is not None:
key = ("loader", path.path)
if key in context.attributes and context.attributes[key].strategy == (
("selectinload_polymorphic", True),
):
selectin_load_via = mapper._should_selectin_load(
context.attributes[key].local_opts["entities"],
_polymorphic_from,
)
else:
selectin_load_via = mapper._should_selectin_load(
None, _polymorphic_from
)
if selectin_load_via and selectin_load_via is not _polymorphic_from:
# only_load_props goes w/ refresh_state only, and in a refresh
# we are a single row query for the exact entity; polymorphic
# loading does not apply
assert only_load_props is None
callable_ = _load_subclass_via_in(context, path, selectin_load_via)
PostLoad.callable_for_path(
context,
load_path,
selectin_load_via.mapper,
selectin_load_via,
callable_,
selectin_load_via,
)
post_load = PostLoad.for_context(context, load_path, only_load_props)
if refresh_state:
refresh_identity_key = refresh_state.key
if refresh_identity_key is None:
# super-rare condition; a refresh is being called
# on a non-instance-key instance; this is meant to only
# occur within a flush()
refresh_identity_key = mapper._identity_key_from_state(
refresh_state
)
else:
refresh_identity_key = None
primary_key_getter = getters["primary_key_getter"]
if mapper.allow_partial_pks:
is_not_primary_key = _none_set.issuperset
else:
is_not_primary_key = _none_set.intersection
def _instance(row):
# determine the state that we'll be populating
if refresh_identity_key:
# fixed state that we're refreshing
state = refresh_state
instance = state.obj()
dict_ = instance_dict(instance)
isnew = state.runid != runid
currentload = True
loaded_instance = False
else:
# look at the row, see if that identity is in the
# session, or we have to create a new one
identitykey = (
identity_class,
primary_key_getter(row),
identity_token,
)
instance = session_identity_map.get(identitykey)
if instance is not None:
# existing instance
state = instance_state(instance)
dict_ = instance_dict(instance)
isnew = state.runid != runid
currentload = not isnew
loaded_instance = False
if version_check and version_id_getter and not currentload:
_validate_version_id(
mapper, state, dict_, row, version_id_getter
)
else:
# create a new instance
# check for non-NULL values in the primary key columns,
# else no entity is returned for the row
if is_not_primary_key(identitykey[1]):
return None
isnew = True
currentload = True
loaded_instance = True
instance = mapper.class_manager.new_instance()
dict_ = instance_dict(instance)
state = instance_state(instance)
state.key = identitykey
state.identity_token = identity_token
# attach instance to session.
state.session_id = session_id
session_identity_map._add_unpresent(state, identitykey)
effective_populate_existing = populate_existing
if refresh_state is state:
effective_populate_existing = True
# populate. this looks at whether this state is new
# for this load or was existing, and whether or not this
# row is the first row with this identity.
if currentload or effective_populate_existing:
# full population routines. Objects here are either
# just created, or we are doing a populate_existing
# be conservative about setting load_path when populate_existing
# is in effect; want to maintain options from the original
# load. see test_expire->test_refresh_maintains_deferred_options
if isnew and (
propagated_loader_options or not effective_populate_existing
):
state.load_options = propagated_loader_options
state.load_path = load_path
_populate_full(
context,
row,
state,
dict_,
isnew,
load_path,
loaded_instance,
effective_populate_existing,
populators,
)
if isnew:
# state.runid should be equal to context.runid / runid
# here, however for event checks we are being more conservative
# and checking against existing run id
# assert state.runid == runid
existing_runid = state.runid
if loaded_instance:
if load_evt:
state.manager.dispatch.load(state, context)
if state.runid != existing_runid:
_warn_for_runid_changed(state)
if persistent_evt:
loaded_as_persistent(context.session, state)
if state.runid != existing_runid:
_warn_for_runid_changed(state)
elif refresh_evt:
state.manager.dispatch.refresh(
state, context, only_load_props
)
if state.runid != runid:
_warn_for_runid_changed(state)
if effective_populate_existing or state.modified:
if refresh_state and only_load_props:
state._commit(dict_, only_load_props)
else:
state._commit_all(dict_, session_identity_map)
if post_load:
post_load.add_state(state, True)
else:
# partial population routines, for objects that were already
# in the Session, but a row matches them; apply eager loaders
# on existing objects, etc.
unloaded = state.unloaded
isnew = state not in context.partials
if not isnew or unloaded or populators["eager"]:
# state is having a partial set of its attributes
# refreshed. Populate those attributes,
# and add to the "context.partials" collection.
to_load = _populate_partial(
context,
row,
state,
dict_,
isnew,
load_path,
unloaded,
populators,
)
if isnew:
if refresh_evt:
existing_runid = state.runid
state.manager.dispatch.refresh(state, context, to_load)
if state.runid != existing_runid:
_warn_for_runid_changed(state)
state._commit(dict_, to_load)
if post_load and context.invoke_all_eagers:
post_load.add_state(state, False)
return instance
if mapper.polymorphic_map and not _polymorphic_from and not refresh_state:
# if we are doing polymorphic, dispatch to a different _instance()
# method specific to the subclass mapper
def ensure_no_pk(row):
identitykey = (
identity_class,
primary_key_getter(row),
identity_token,
)
if not is_not_primary_key(identitykey[1]):
return identitykey
else:
return None
_instance = _decorate_polymorphic_switch(
_instance,
context,
query_entity,
mapper,
result,
path,
polymorphic_discriminator,
adapter,
ensure_no_pk,
)
return _instance
def _load_subclass_via_in(context, path, entity):
mapper = entity.mapper
zero_idx = len(mapper.base_mapper.primary_key) == 1
if entity.is_aliased_class:
q, enable_opt, disable_opt = mapper._subclass_load_via_in(entity)
else:
q, enable_opt, disable_opt = mapper._subclass_load_via_in_mapper
def do_load(context, path, states, load_only, effective_entity):
orig_query = context.query
q2 = q._with_lazyload_options(
(enable_opt,) + orig_query._with_options + (disable_opt,),
path.parent,
cache_path=path,
)
if context.populate_existing:
q2.add_criteria(lambda q: q.populate_existing())
q2(context.session).params(
primary_keys=[
state.key[1][0] if zero_idx else state.key[1]
for state, load_attrs in states
]
).all()
return do_load
def _populate_full(
context,
row,
state,
dict_,
isnew,
load_path,
loaded_instance,
populate_existing,
populators,
):
if isnew:
# first time we are seeing a row with this identity.
state.runid = context.runid
for key, getter in populators["quick"]:
dict_[key] = getter(row)
if populate_existing:
for key, set_callable in populators["expire"]:
dict_.pop(key, None)
if set_callable:
state.expired_attributes.add(key)
else:
for key, set_callable in populators["expire"]:
if set_callable:
state.expired_attributes.add(key)
for key, populator in populators["new"]:
populator(state, dict_, row)
for key, populator in populators["delayed"]:
populator(state, dict_, row)
elif load_path != state.load_path:
# new load path, e.g. object is present in more than one
# column position in a series of rows
state.load_path = load_path
# if we have data, and the data isn't in the dict, OK, let's put
# it in.
for key, getter in populators["quick"]:
if key not in dict_:
dict_[key] = getter(row)
# otherwise treat like an "already seen" row
for key, populator in populators["existing"]:
populator(state, dict_, row)
# TODO: allow "existing" populator to know this is
# a new path for the state:
# populator(state, dict_, row, new_path=True)
else:
# have already seen rows with this identity in this same path.
for key, populator in populators["existing"]:
populator(state, dict_, row)
# TODO: same path
# populator(state, dict_, row, new_path=False)
def _populate_partial(
context, row, state, dict_, isnew, load_path, unloaded, populators
):
if not isnew:
to_load = context.partials[state]
for key, populator in populators["existing"]:
if key in to_load:
populator(state, dict_, row)
else:
to_load = unloaded
context.partials[state] = to_load
for key, getter in populators["quick"]:
if key in to_load:
dict_[key] = getter(row)
for key, set_callable in populators["expire"]:
if key in to_load:
dict_.pop(key, None)
if set_callable:
state.expired_attributes.add(key)
for key, populator in populators["new"]:
if key in to_load:
populator(state, dict_, row)
for key, populator in populators["delayed"]:
if key in to_load:
populator(state, dict_, row)
for key, populator in populators["eager"]:
if key not in unloaded:
populator(state, dict_, row)
return to_load
def _validate_version_id(mapper, state, dict_, row, getter):
if mapper._get_state_attr_by_column(
state, dict_, mapper.version_id_col
) != getter(row):
raise orm_exc.StaleDataError(
"Instance '%s' has version id '%s' which "
"does not match database-loaded version id '%s'."
% (
state_str(state),
mapper._get_state_attr_by_column(
state, dict_, mapper.version_id_col
),
getter(row),
)
)
def _decorate_polymorphic_switch(
instance_fn,
context,
query_entity,
mapper,
result,
path,
polymorphic_discriminator,
adapter,
ensure_no_pk,
):
if polymorphic_discriminator is not None:
polymorphic_on = polymorphic_discriminator
else:
polymorphic_on = mapper.polymorphic_on
if polymorphic_on is None:
return instance_fn
if adapter:
polymorphic_on = adapter.columns[polymorphic_on]
def configure_subclass_mapper(discriminator):
try:
sub_mapper = mapper.polymorphic_map[discriminator]
except KeyError:
raise AssertionError(
"No such polymorphic_identity %r is defined" % discriminator
)
else:
if sub_mapper is mapper:
return None
elif not sub_mapper.isa(mapper):
return False
return _instance_processor(
query_entity,
sub_mapper,
context,
result,
path,
adapter,
_polymorphic_from=mapper,
)
polymorphic_instances = util.PopulateDict(configure_subclass_mapper)
getter = result._getter(polymorphic_on)
def polymorphic_instance(row):
discriminator = getter(row)
if discriminator is not None:
_instance = polymorphic_instances[discriminator]
if _instance:
return _instance(row)
elif _instance is False:
identitykey = ensure_no_pk(row)
if identitykey:
raise sa_exc.InvalidRequestError(
"Row with identity key %s can't be loaded into an "
"object; the polymorphic discriminator column '%s' "
"refers to %s, which is not a sub-mapper of "
"the requested %s"
% (
identitykey,
polymorphic_on,
mapper.polymorphic_map[discriminator],
mapper,
)
)
else:
return None
else:
return instance_fn(row)
else:
identitykey = ensure_no_pk(row)
if identitykey:
raise sa_exc.InvalidRequestError(
"Row with identity key %s can't be loaded into an "
"object; the polymorphic discriminator column '%s' is "
"NULL" % (identitykey, polymorphic_on)
)
else:
return None
return polymorphic_instance
class PostLoad(object):
"""Track loaders and states for "post load" operations."""
__slots__ = "loaders", "states", "load_keys"
def __init__(self):
self.loaders = {}
self.states = util.OrderedDict()
self.load_keys = None
def add_state(self, state, overwrite):
# the states for a polymorphic load here are all shared
# within a single PostLoad object among multiple subtypes.
# Filtering of callables on a per-subclass basis needs to be done at
# the invocation level
self.states[state] = overwrite
def invoke(self, context, path):
if not self.states:
return
path = path_registry.PathRegistry.coerce(path)
for token, limit_to_mapper, loader, arg, kw in self.loaders.values():
states = [
(state, overwrite)
for state, overwrite in self.states.items()
if state.manager.mapper.isa(limit_to_mapper)
]
if states:
loader(context, path, states, self.load_keys, *arg, **kw)
self.states.clear()
@classmethod
def for_context(cls, context, path, only_load_props):
pl = context.post_load_paths.get(path.path)
if pl is not None and only_load_props:
pl.load_keys = only_load_props
return pl
@classmethod
def path_exists(self, context, path, key):
return (
path.path in context.post_load_paths
and key in context.post_load_paths[path.path].loaders
)
@classmethod
def callable_for_path(
cls, context, path, limit_to_mapper, token, loader_callable, *arg, **kw
):
if path.path in context.post_load_paths:
pl = context.post_load_paths[path.path]
else:
pl = context.post_load_paths[path.path] = PostLoad()
pl.loaders[token] = (token, limit_to_mapper, loader_callable, arg, kw)
def load_scalar_attributes(mapper, state, attribute_names, passive):
"""initiate a column-based attribute refresh operation."""
# assert mapper is _state_mapper(state)
session = state.session
if not session:
raise orm_exc.DetachedInstanceError(
"Instance %s is not bound to a Session; "
"attribute refresh operation cannot proceed" % (state_str(state))
)
has_key = bool(state.key)
result = False
no_autoflush = (
bool(passive & attributes.NO_AUTOFLUSH) or state.session.autocommit
)
# in the case of inheritance, particularly concrete and abstract
# concrete inheritance, the class manager might have some keys
# of attributes on the superclass that we didn't actually map.
# These could be mapped as "concrete, don't load" or could be completely
# excluded from the mapping and we know nothing about them. Filter them
# here to prevent them from coming through.
if attribute_names:
attribute_names = attribute_names.intersection(mapper.attrs.keys())
if mapper.inherits and not mapper.concrete:
# because we are using Core to produce a select() that we
# pass to the Query, we aren't calling setup() for mapped
# attributes; in 1.0 this means deferred attrs won't get loaded
# by default
statement = mapper._optimized_get_statement(state, attribute_names)
if statement is not None:
# this was previously aliased(mapper, statement), however,
# statement is a select() and Query's coercion now raises for this
# since you can't "select" from a "SELECT" statement. only
# from_statement() allows this.
# note: using from_statement() here means there is an adaption
# with adapt_on_names set up. the other option is to make the
# aliased() against a subquery which affects the SQL.
from .query import FromStatement
stmt = FromStatement(mapper, statement).options(
strategy_options.Load(mapper).undefer("*")
)
result = load_on_ident(
session,
stmt,
None,
only_load_props=attribute_names,
refresh_state=state,
no_autoflush=no_autoflush,
)
if result is False:
if has_key:
identity_key = state.key
else:
# this codepath is rare - only valid when inside a flush, and the
# object is becoming persistent but hasn't yet been assigned
# an identity_key.
# check here to ensure we have the attrs we need.
pk_attrs = [
mapper._columntoproperty[col].key for col in mapper.primary_key
]
if state.expired_attributes.intersection(pk_attrs):
raise sa_exc.InvalidRequestError(
"Instance %s cannot be refreshed - it's not "
" persistent and does not "
"contain a full primary key." % state_str(state)
)
identity_key = mapper._identity_key_from_state(state)
if (
_none_set.issubset(identity_key) and not mapper.allow_partial_pks
) or _none_set.issuperset(identity_key):
util.warn_limited(
"Instance %s to be refreshed doesn't "
"contain a full primary key - can't be refreshed "
"(and shouldn't be expired, either).",
state_str(state),
)
return
result = load_on_ident(
session,
future.select(mapper).set_label_style(
LABEL_STYLE_TABLENAME_PLUS_COL
),
identity_key,
refresh_state=state,
only_load_props=attribute_names,
no_autoflush=no_autoflush,
)
# if instance is pending, a refresh operation
# may not complete (even if PK attributes are assigned)
if has_key and result is None:
raise orm_exc.ObjectDeletedError(state)