On 12/27/2011 5:34 PM, Michael Bayer wrote:
On Dec 27, 2011, at 5:21 PM, Kent wrote:
So see what happens if you, for the moment, just monkeypatch over
orm.session._state_session to do a lookup in a global context if
state.session_id isn't set. If that solves the problem of "I want
detached objects to load stuff", for you and everyone else who wants
this feature, then whatever - I'm not at all thrilled about this use
case but if it's just one trivial hook that I don't need to
encourage, then there you go.
Please give me a lesson in monkeypatching 101. This isn't being
invoked:
=====================
import sqlalchemy.orm.session as session_module
sqla_state_session = session_module._state_session
def _state_session(state):
"""
for transient/detached objects, so we can automatically query
these related objects
"""
return sqla_state_session(state) or DBSession()
setattr(session_module, '_state_session', _state_session)
=====================
I presume there are already references to _state_session before I
change it.
Hm I would have guessed, but mapper.py and strategies.py seem to be
calling it relative to the module. What does pdb tell you if you
post mortem into where it raises the Detached error ?
Also, will this cause other side effects, such as obj in DBSession
reporting True when it used to report False or the orm internals being
confused by the return of this value?
maybe ? if it doesn't just work then yes. The new logic here only
needs to take place at the point at which it loads an attribute so if
we made it local to those areas, there shouldn't be any big issues.
I'm basically making you a developer here to help me test this out.
ok, it was never making it that far because my main use case for this is
to work with transient instances (detached are secondary). I was
testing with a transient object and it never got past the first if
statement in _load_for_state(), which was using session_id instead of
the return value from _state_session().
So we'd have to move the state_session API invocation up (patch
attached). Then this works as a proof of concept for both detached and
transient objects.
I'm not sure if it was important for the "return attributes.ATTR_EMPTY"
to have precedence over "return attributes.PASSIVE_NO_RESULT" so I kept
them in that order to not disturb anything (otherwise we could delay the
session lookup until after the "return attributes.PASSIVE_NO_RESULT"
test). Those cases shouldn't be common anyway, right?
We'd also need to make this very local to the loading of attributes, as
you mentioned, because object_session() also invokes _state_session()...
we can't have that.. it messes up too much. (For example, transient
objects appear pending and detached objects appear persistent, depending
on your method of inspection.)
Off topic, but from a shell prompt I sometimes find myself naturally
attempting this:
session.detach(instance)
and then when that fails, I remember:
session.expunge(instance)
I'm not asking for a change here, but quite curious: you think 'detach'
is a better/more natural term?
=============================
diff -U10 -r sqlalchemy-default/lib/sqlalchemy/orm/strategies.py
sqlalchemy-default.kb/lib/sqlalchemy/orm/strategies.py
--- sqlalchemy-default/lib/sqlalchemy/orm/strategies.py 2011-12-15
11:42:50.000000000 -0500
+++ sqlalchemy-default.kb/lib/sqlalchemy/orm/strategies.py
2011-12-27 17:48:54.000000000 -0500
@@ -450,41 +450,42 @@
self._rev_bind_to_col, \
self._rev_equated_columns
criterion = sql_util.adapt_criterion_to_null(criterion,
bind_to_col)
if adapt_source:
criterion = adapt_source(criterion)
return criterion
def _load_for_state(self, state, passive):
- if not state.key and \
- (not self.parent_property.load_on_pending or not
state.session_id):
+ prop = self.parent_property
+ pending = not state.key
+ session = sessionlib._state_session(state)
+
+ if pending and \
+ (not prop.load_on_pending or not session):
return attributes.ATTR_EMPTY
instance_mapper = state.manager.mapper
- prop = self.parent_property
key = self.key
prop_mapper = self.mapper
- pending = not state.key
if (
(passive is attributes.PASSIVE_NO_FETCH or \
passive is attributes.PASSIVE_NO_FETCH_RELATED) and
not self.use_get
) or (
passive is attributes.PASSIVE_ONLY_PERSISTENT and
pending
):
return attributes.PASSIVE_NO_RESULT
- session = sessionlib._state_session(state)
if not session:
raise orm_exc.DetachedInstanceError(
"Parent instance %s is not bound to a Session; "
"lazy load operation of attribute '%s' cannot proceed" %
(mapperutil.state_str(state), key)
)
# if we have a simple primary key load, check the
# identity map without generating a Query at all
if self.use_get:
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diff -U10 -r sqlalchemy-default/lib/sqlalchemy/orm/strategies.py
sqlalchemy-default.kb/lib/sqlalchemy/orm/strategies.py
--- sqlalchemy-default/lib/sqlalchemy/orm/strategies.py 2011-12-15
11:42:50.000000000 -0500
+++ sqlalchemy-default.kb/lib/sqlalchemy/orm/strategies.py 2011-12-27
17:48:54.000000000 -0500
@@ -450,41 +450,42 @@
self._rev_bind_to_col, \
self._rev_equated_columns
criterion = sql_util.adapt_criterion_to_null(criterion, bind_to_col)
if adapt_source:
criterion = adapt_source(criterion)
return criterion
def _load_for_state(self, state, passive):
- if not state.key and \
- (not self.parent_property.load_on_pending or not state.session_id):
+ prop = self.parent_property
+ pending = not state.key
+ session = sessionlib._state_session(state)
+
+ if pending and \
+ (not prop.load_on_pending or not session):
return attributes.ATTR_EMPTY
instance_mapper = state.manager.mapper
- prop = self.parent_property
key = self.key
prop_mapper = self.mapper
- pending = not state.key
if (
(passive is attributes.PASSIVE_NO_FETCH or \
passive is attributes.PASSIVE_NO_FETCH_RELATED) and
not self.use_get
) or (
passive is attributes.PASSIVE_ONLY_PERSISTENT and
pending
):
return attributes.PASSIVE_NO_RESULT
- session = sessionlib._state_session(state)
if not session:
raise orm_exc.DetachedInstanceError(
"Parent instance %s is not bound to a Session; "
"lazy load operation of attribute '%s' cannot proceed" %
(mapperutil.state_str(state), key)
)
# if we have a simple primary key load, check the
# identity map without generating a Query at all
if self.use_get:
