Mini Shell
# 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
import collections
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 _SET_DEFERRED_EXPIRED
from .util import _none_set
from .util import state_str
from .. import exc as sa_exc
from .. import util
from ..sql import util as sql_util
_new_runid = util.counter()
def instances(query, cursor, context):
"""Return an ORM result as an iterator."""
context.runid = _new_runid()
context.post_load_paths = {}
filtered = query._has_mapper_entities
single_entity = query.is_single_entity
if filtered:
if single_entity:
filter_fn = id
else:
def filter_fn(row):
return tuple(
id(item) if ent.use_id_for_hash else item
for ent, item in zip(query._entities, row)
)
try:
(process, labels) = list(
zip(
*[
query_entity.row_processor(query, context, cursor)
for query_entity in query._entities
]
)
)
if not single_entity:
keyed_tuple = util.lightweight_named_tuple("result", labels)
while True:
context.partials = {}
if query._yield_per:
fetch = cursor.fetchmany(query._yield_per)
if not fetch:
break
else:
fetch = cursor.fetchall()
if single_entity:
proc = process[0]
rows = [proc(row) for row in fetch]
else:
rows = [
keyed_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)
if filtered:
rows = util.unique_list(rows, filter_fn)
for row in rows:
yield row
if not query._yield_per:
break
except Exception:
with util.safe_reraise():
cursor.close()
@util.dependencies("sqlalchemy.orm.query")
def merge_result(querylib, query, iterator, load=True):
"""Merge a result into this :class:`_query.Query` object's Session."""
session = query.session
if load:
# flush current contents if we expect to load data
session._autoflush()
autoflush = session.autoflush
try:
session.autoflush = False
single_entity = len(query._entities) == 1
if single_entity:
if isinstance(query._entities[0], querylib._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(query._entities)
if isinstance(e, querylib._MapperEntity)
]
result = []
keys = [ent._label_name for ent in query._entities]
keyed_tuple = util.lightweight_named_tuple("result", keys)
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))
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
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(
query, key, refresh_state=None, with_for_update=None, only_load_props=None
):
"""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(
query,
ident,
refresh_state=refresh_state,
with_for_update=with_for_update,
only_load_props=only_load_props,
identity_token=identity_token,
)
def load_on_pk_identity(
query,
primary_key_identity,
refresh_state=None,
with_for_update=None,
only_load_props=None,
identity_token=None,
):
"""Load the given primary key identity from the database."""
if refresh_state is None:
q = query._clone()
q._get_condition()
else:
q = query._clone()
if primary_key_identity is not None:
mapper = query._mapper_zero()
(_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."
)
_get_clause = q._adapt_clause(_get_clause, True, False)
q._criterion = _get_clause
params = dict(
[
(_get_params[primary_key].key, id_val)
for id_val, primary_key in zip(
primary_key_identity, mapper.primary_key
)
]
)
q._params = params
# with_for_update needs to be query.LockmodeArg()
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
q._get_options(
populate_existing=bool(refresh_state),
version_check=version_check,
only_load_props=only_load_props,
refresh_state=refresh_state,
identity_token=identity_token,
)
q._order_by = None
try:
return q.one()
except orm_exc.NoResultFound:
return None
def _setup_entity_query(
context,
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(context.attributes, "memoized_setups", quick_populators)
for value in poly_properties:
if only_load_props and value.key not in only_load_props:
continue
value.setup(
context,
query_entity,
path,
adapter,
only_load_props=only_load_props,
column_collection=column_collection,
memoized_populators=quick_populators,
**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(
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.
pk_cols = mapper.primary_key
if adapter:
pk_cols = [adapter.columns[c] for c in pk_cols]
identity_class = mapper._identity_class
populators = collections.defaultdict(list)
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
)
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:
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.
populators["expire"].append((prop.key, False))
else:
getter = None
# the "adapter" can be here via different paths,
# e.g. via adapter present at setup_query or adapter
# applied to the query afterwards via eager load subquery.
# If the column here
# were already a product of this adapter, sending it through
# the adapter again can return a totally new expression that
# won't be recognized in the result, and the ColumnAdapter
# currently does not accommodate for this. OTOH, if the
# column were never applied through this adapter, we may get
# None back, in which case we still won't get our "getter".
# so try both against result._getter(). See issue #4048
if adapter:
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:
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, path, mapper, result, adapter, populators
)
else:
prop.create_row_processor(
context, path, mapper, result, adapter, populators
)
propagate_options = context.propagate_options
load_path = (
context.query._current_path + path
if context.query._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
version_check = context.version_check
runid = context.runid
identity_token = context.identity_token
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
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,
tuple([row[column] for column in pk_cols]),
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 not currentload:
_validate_version_id(mapper, state, dict_, row, adapter)
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)
# 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 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 (propagate_options or not populate_existing):
state.load_options = propagate_options
state.load_path = load_path
_populate_full(
context,
row,
state,
dict_,
isnew,
load_path,
loaded_instance,
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 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
_instance = _decorate_polymorphic_switch(
_instance,
context,
mapper,
result,
path,
polymorphic_discriminator,
adapter,
)
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 orig_query._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, adapter):
version_id_col = mapper.version_id_col
if version_id_col is None:
return
if adapter:
version_id_col = adapter.columns[version_id_col]
if (
mapper._get_state_attr_by_column(state, dict_, mapper.version_id_col)
!= row[version_id_col]
):
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
),
row[version_id_col],
)
)
def _decorate_polymorphic_switch(
instance_fn,
context,
mapper,
result,
path,
polymorphic_discriminator,
adapter,
):
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
return _instance_processor(
sub_mapper,
context,
result,
path,
adapter,
_polymorphic_from=mapper,
)
polymorphic_instances = util.PopulateDict(configure_subclass_mapper)
def polymorphic_instance(row):
discriminator = row[polymorphic_on]
if discriminator is not None:
_instance = polymorphic_instances[discriminator]
if _instance:
return _instance(row)
return instance_fn(row)
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):
"""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
# 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, dont 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:
result = load_on_ident(
session.query(mapper)
.options(strategy_options.Load(mapper).undefer("*"))
.from_statement(statement),
None,
only_load_props=attribute_names,
refresh_state=state,
)
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.query(mapper),
identity_key,
refresh_state=state,
only_load_props=attribute_names,
)
# 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)
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