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calibre-web/vendor/sqlalchemy/orm/loading.py
2016-04-27 17:47:31 +02:00

607 lines
21 KiB
Python

# orm/loading.py
# Copyright (C) 2005-2013 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 util
from . import attributes, exc as orm_exc, state as statelib
from .interfaces import EXT_CONTINUE
from ..sql import util as sql_util
from .util import _none_set, state_str
from .. import exc as sa_exc
sessionlib = util.importlater("sqlalchemy.orm", "session")
_new_runid = util.counter()
def instances(query, cursor, context):
"""Return an ORM result as an iterator."""
session = query.session
context.runid = _new_runid()
filter_fns = [ent.filter_fn
for ent in query._entities]
filtered = id in filter_fns
single_entity = filtered and len(query._entities) == 1
if filtered:
if single_entity:
filter_fn = id
else:
def filter_fn(row):
return tuple(fn(x) for x, fn in zip(row, filter_fns))
custom_rows = single_entity and \
query._entities[0].mapper.dispatch.append_result
(process, labels) = \
zip(*[
query_entity.row_processor(query,
context, custom_rows)
for query_entity in query._entities
])
while True:
context.progress = {}
context.partials = {}
if query._yield_per:
fetch = cursor.fetchmany(query._yield_per)
if not fetch:
break
else:
fetch = cursor.fetchall()
if custom_rows:
rows = []
for row in fetch:
process[0](row, rows)
elif single_entity:
rows = [process[0](row, None) for row in fetch]
else:
rows = [util.KeyedTuple([proc(row, None) for proc in process],
labels) for row in fetch]
if filtered:
rows = util.unique_list(rows, filter_fn)
if context.refresh_state and query._only_load_props \
and context.refresh_state in context.progress:
context.refresh_state._commit(
context.refresh_state.dict, query._only_load_props)
context.progress.pop(context.refresh_state)
statelib.InstanceState._commit_all_states(
context.progress.items(),
session.identity_map
)
for state, (dict_, attrs) in context.partials.iteritems():
state._commit(dict_, attrs)
for row in rows:
yield row
if not query._yield_per:
break
def merge_result(query, iterator, load=True):
"""Merge a result into this :class:`.Query` object's Session."""
from . import query as querylib
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={})
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]
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={})
result.append(util.KeyedTuple(newrow, keys))
return iter(result)
finally:
session.autoflush = autoflush
def get_from_identity(session, 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)
# 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(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, lockmode=None,
only_load_props=None):
"""Load the given identity key from the database."""
lockmode = lockmode or query._lockmode
if key is not None:
ident = key[1]
else:
ident = None
if refresh_state is None:
q = query._clone()
q._get_condition()
else:
q = query._clone()
if ident 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 ident:
nones = set([
_get_params[col].key for col, value in
zip(mapper.primary_key, ident) if value is None
])
_get_clause = sql_util.adapt_criterion_to_null(
_get_clause, nones)
_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(ident, mapper.primary_key)
])
q._params = params
if lockmode is not None:
q._lockmode = lockmode
q._get_options(
populate_existing=bool(refresh_state),
version_check=(lockmode is not None),
only_load_props=only_load_props,
refresh_state=refresh_state)
q._order_by = None
try:
return q.one()
except orm_exc.NoResultFound:
return None
def instance_processor(mapper, context, path, adapter,
polymorphic_from=None,
only_load_props=None,
refresh_state=None,
polymorphic_discriminator=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 polymorphic_from or refresh_state:
polymorphic_on = None
else:
if polymorphic_discriminator is not None:
polymorphic_on = polymorphic_discriminator
else:
polymorphic_on = mapper.polymorphic_on
polymorphic_instances = util.PopulateDict(
_configure_subclass_mapper(
mapper,
context, path, adapter)
)
version_id_col = mapper.version_id_col
if adapter:
pk_cols = [adapter.columns[c] for c in pk_cols]
if polymorphic_on is not None:
polymorphic_on = adapter.columns[polymorphic_on]
if version_id_col is not None:
version_id_col = adapter.columns[version_id_col]
identity_class = mapper._identity_class
new_populators = []
existing_populators = []
eager_populators = []
load_path = context.query._current_path + path \
if context.query._current_path.path \
else path
def populate_state(state, dict_, row, isnew, only_load_props):
if isnew:
if context.propagate_options:
state.load_options = context.propagate_options
if state.load_options:
state.load_path = load_path
if not new_populators:
_populators(mapper, context, path, row, adapter,
new_populators,
existing_populators,
eager_populators
)
if isnew:
populators = new_populators
else:
populators = existing_populators
if only_load_props is None:
for key, populator in populators:
populator(state, dict_, row)
elif only_load_props:
for key, populator in populators:
if key in only_load_props:
populator(state, dict_, row)
session_identity_map = context.session.identity_map
listeners = mapper.dispatch
translate_row = listeners.translate_row or None
create_instance = listeners.create_instance or None
populate_instance = listeners.populate_instance or None
append_result = listeners.append_result or None
populate_existing = context.populate_existing or mapper.always_refresh
invoke_all_eagers = context.invoke_all_eagers
if mapper.allow_partial_pks:
is_not_primary_key = _none_set.issuperset
else:
is_not_primary_key = _none_set.issubset
def _instance(row, result):
if not new_populators and invoke_all_eagers:
_populators(mapper, context, path, row, adapter,
new_populators,
existing_populators,
eager_populators
)
if translate_row:
for fn in translate_row:
ret = fn(mapper, context, row)
if ret is not EXT_CONTINUE:
row = ret
break
if polymorphic_on is not None:
discriminator = row[polymorphic_on]
if discriminator is not None:
_instance = polymorphic_instances[discriminator]
if _instance:
return _instance(row, result)
# determine identity key
if refresh_state:
identitykey = refresh_state.key
if identitykey 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()
identitykey = mapper._identity_key_from_state(refresh_state)
else:
identitykey = (
identity_class,
tuple([row[column] for column in pk_cols])
)
instance = session_identity_map.get(identitykey)
if instance is not None:
state = attributes.instance_state(instance)
dict_ = attributes.instance_dict(instance)
isnew = state.runid != context.runid
currentload = not isnew
loaded_instance = False
if not currentload and \
version_id_col is not None and \
context.version_check and \
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]))
elif refresh_state:
# out of band refresh_state detected (i.e. its not in the
# session.identity_map) honor it anyway. this can happen
# if a _get() occurs within save_obj(), such as
# when eager_defaults is True.
state = refresh_state
instance = state.obj()
dict_ = attributes.instance_dict(instance)
isnew = state.runid != context.runid
currentload = True
loaded_instance = False
else:
# 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
if create_instance:
for fn in create_instance:
instance = fn(mapper, context,
row, mapper.class_)
if instance is not EXT_CONTINUE:
manager = attributes.manager_of_class(
instance.__class__)
# TODO: if manager is None, raise a friendly error
# about returning instances of unmapped types
manager.setup_instance(instance)
break
else:
instance = mapper.class_manager.new_instance()
else:
instance = mapper.class_manager.new_instance()
dict_ = attributes.instance_dict(instance)
state = attributes.instance_state(instance)
state.key = identitykey
# attach instance to session.
state.session_id = context.session.hash_key
session_identity_map.add(state)
if currentload or populate_existing:
# state is being fully loaded, so populate.
# add to the "context.progress" collection.
if isnew:
state.runid = context.runid
context.progress[state] = dict_
if populate_instance:
for fn in populate_instance:
ret = fn(mapper, context, row, state,
only_load_props=only_load_props,
instancekey=identitykey, isnew=isnew)
if ret is not EXT_CONTINUE:
break
else:
populate_state(state, dict_, row, isnew, only_load_props)
else:
populate_state(state, dict_, row, isnew, only_load_props)
if loaded_instance:
state.manager.dispatch.load(state, context)
elif isnew:
state.manager.dispatch.refresh(state, context, only_load_props)
elif state in context.partials or state.unloaded or eager_populators:
# state is having a partial set of its attributes
# refreshed. Populate those attributes,
# and add to the "context.partials" collection.
if state in context.partials:
isnew = False
(d_, attrs) = context.partials[state]
else:
isnew = True
attrs = state.unloaded
context.partials[state] = (dict_, attrs)
if populate_instance:
for fn in populate_instance:
ret = fn(mapper, context, row, state,
only_load_props=attrs,
instancekey=identitykey, isnew=isnew)
if ret is not EXT_CONTINUE:
break
else:
populate_state(state, dict_, row, isnew, attrs)
else:
populate_state(state, dict_, row, isnew, attrs)
for key, pop in eager_populators:
if key not in state.unloaded:
pop(state, dict_, row)
if isnew:
state.manager.dispatch.refresh(state, context, attrs)
if result is not None:
if append_result:
for fn in append_result:
if fn(mapper, context, row, state,
result, instancekey=identitykey,
isnew=isnew) is not EXT_CONTINUE:
break
else:
result.append(instance)
else:
result.append(instance)
return instance
return _instance
def _populators(mapper, context, path, row, adapter,
new_populators, existing_populators, eager_populators):
"""Produce a collection of attribute level row processor
callables."""
delayed_populators = []
pops = (new_populators, existing_populators, delayed_populators,
eager_populators)
for prop in mapper._props.itervalues():
for i, pop in enumerate(prop.create_row_processor(
context,
path,
mapper, row, adapter)):
if pop is not None:
pops[i].append((prop.key, pop))
if delayed_populators:
new_populators.extend(delayed_populators)
def _configure_subclass_mapper(mapper, context, path, adapter):
"""Produce a mapper level row processor callable factory for mappers
inheriting this one."""
def configure_subclass_mapper(discriminator):
try:
sub_mapper = mapper.polymorphic_map[discriminator]
except KeyError:
raise AssertionError(
"No such polymorphic_identity %r is defined" %
discriminator)
if sub_mapper is mapper:
return None
return instance_processor(
sub_mapper,
context,
path,
adapter,
polymorphic_from=mapper)
return configure_subclass_mapper
def load_scalar_attributes(mapper, state, attribute_names):
"""initiate a column-based attribute refresh operation."""
#assert mapper is _state_mapper(state)
session = sessionlib._state_session(state)
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
if mapper.inherits and not mapper.concrete:
statement = mapper._optimized_get_statement(state, attribute_names)
if statement is not None:
result = load_on_ident(
session.query(mapper).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("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)