Reusing the original query is hard, and the case you have is due to
mismatched entities that would have to be handled, probably by wrapping the
original query in a subquery just like subquery eager loading does. The
subquery eager loading feature took a few years to work out an enormous
number of issues with this approach.
The new feature which I'm now working on, several hours a day, in response
to this thread solves the whole problem in a much better way, using a
simple IN expression against the primary keys of all states loaded in the
query. Betas of 1.2 will hopefully be available in a month or two. The
feature can be replicated in older versions by just grabbing the list of
states coming out of __iter__ and using their primary keys in an IN clause.
Parallel development of this other approach as an interim throwaway is
probably not worth it if it continues to become more complicated.
On Apr 4, 2017 7:02 PM, <da...@benchling.com> wrote:
Hey Mike,
Thanks for those -- seems to have helped those cases, though we're running
into some pretty weird behavior with joins. Here's a simplified case that
shows one of the issues we're running into (use _loader_from_cls from
above):
class W(Base):
__tablename__ = 'w'
id = Column(Integer, primary_key=True)
type = Column(String)
x_id = Column(Integer, ForeignKey('x.id'))
x = relationship('X')
__mapper_args__ = {'polymorphic_on': type}
class W2(W):
__tablename__ = 'w2'
id = Column(Integer, ForeignKey('w.id'), primary_key=True)
w2 = Column(String)
__mapper_args__ = {'polymorphic_identity': 'w2'}
class X(Base):
__tablename__ = 'x'
id = Column(Integer, primary_key=True)
@event.listens_for(W, "load", propagate=True)
def load_extra(target, context):
key = ('loader_by_cls', type(target))
if key not in context.attributes:
context.attributes[key] = _loader_for_cls(target, context)
e = create_engine("sqlite://", echo=True)
Base.metadata.create_all(e)
s = Session(e)
s.add(W2(x=X()))
s.commit()
s.query(W).join(W.x).first()
One of the statements emitted by this is
SELECT w2.id AS w2_id, w.id AS w_id, w.type AS w_type, w.x_id AS w_x_id,
w2.w2 AS w2_w2
FROM w2, w JOIN x ON x.id = w.x_id
LIMIT ? OFFSET ?
Specifically, the "FROM w2, w JOIN x" is not what we want here -- we'd just
want "FROM w2"
Replacing
q = orig_query.with_entities(target_cls)
with
q = context.session.query(target_cls).join(orig_query.subquery())
fixes the issue, though this feels less than ideal. Subclassing Query also
seems less than ideal. Do you have any ideas here?
Thanks,
Damon
On Tuesday, April 4, 2017 at 6:42:32 AM UTC-7, Mike Bayer wrote:
> This repaste of the example contains two refinements to address each of
> these issues distinctly. We want to avoid re-entrant invocation of
> _loader_for_cls, so putting a flag into attributes handles that. Then
> there's the issue of same class coming in that we are already querying,
> we can look at the type being loaded in column_descriptions, and this
> also solves the re-entrant problem though I think the flag is more
> direct. The column_descriptions check likely needs more refinements,
> but the general idea is that if the entity being loaded is already a B2,
> then you wouldn't do any extra B2 queries (unless you have multiple
> levels of inheritance / polymorphic loading in which case that probably
> needs adjustment).
>
> The "strong reference" comment, you can try commenting that out in the
> test and see what happens. Because this loader trick loads all the
> subclasses up front upon seeing the first member of a particular
> subtype, it is loading for subsequent instances that aren't seen yet as
> well. If we don't make a strong reference to them, they get lost and
> the extra attribute loading fails.
>
> The feature I have in development works a lot better because all the
> additional loads are done *after* all the entities are loaded, and it
> does it using an IN query that only includes those entities that
> definitely need the load. I'm not sure if there are other negative side
> effects from our loading of the "subclass" entity in some cases ahead of
> where the primary query gets at the entity. The recipe here could be
> made to do all the extra loads after the primary query but theres no
> "after query" hook, you'd have to subclass Query and override __iter__
> to add this step.
>
> from sqlalchemy import *
> from sqlalchemy.orm import *
> from sqlalchemy.ext.declarative import declarative_base
> from sqlalchemy import event
>
> Base = declarative_base()
>
>
> class A(Base):
> __tablename__ = 'a'
> id = Column(Integer, primary_key=True)
> a1 = Column(String)
> type = Column(String)
>
> __mapper_args__ = {'polymorphic_on': type}
>
>
> class B1(A):
> __tablename__ = 'b1'
> id = Column(Integer, ForeignKey('a.id'), primary_key=True)
> b1 = Column(String)
> b_data = Column(String)
> __mapper_args__ = {'polymorphic_identity': 'b1'}
>
>
> class B2(A):
> __tablename__ = 'b2'
> id = Column(Integer, ForeignKey('a.id'), primary_key=True)
> b2 = Column(String)
> b_data = Column(String)
> cs = relationship("C", lazy='subquery')
>
> __mapper_args__ = {'polymorphic_identity': 'b2'}
>
>
> class C(Base):
> __tablename__ = 'c'
> id = Column(Integer, primary_key=True)
> b2_id = Column(ForeignKey('b2.id'))
>
>
> class B3(A):
> __tablename__ = 'b3'
> id = Column(Integer, ForeignKey('a.id'), primary_key=True)
> b3 = Column(String)
> b_data = Column(String)
> __mapper_args__ = {'polymorphic_identity': 'b3'}
>
>
> def _loader_for_cls(target, context):
> orig_query = context.query
>
> target_cls = type(target)
>
> if orig_query.column_descriptions[0]['type'] is target_cls:
> return None
>
> # take the original query and chance the entity to the subclass
> q = orig_query.with_entities(target_cls)
>
> # defer everything that's not PK / polymorphic_on from A. this whole
> # bit is just to avoid all those extra columns
> to_defer = []
> mapper = inspect(target).mapper
> inherited = mapper.inherits
> while inherited is not None:
> for attr in inherited.column_attrs:
> if not attr.expression.primary_key and \
> attr.expression is not inherited.polymorphic_on:
> to_defer.append(attr.key)
> for attr in inherited.relationships:
> to_defer.append(attr.key)
> inherited = inherited.inherits
> q = q.options(*[defer(k) for k in to_defer])
>
> q._attributes["load_extra_called"] = True
>
> # store this strong reference so recs don't get lost while
> # iterating
> return q.all()
>
>
> @event.listens_for(A, "load", propagate=True)
> def load_extra(target, context):
> if "load_extra_called" in context.attributes:
> return
>
> key = ('loader_by_cls', type(target))
>
> if key not in context.attributes:
> context.attributes[key] = _loader_for_cls(target, context)
>
>
> e = create_engine("sqlite://", echo=True)
> Base.metadata.create_all(e)
>
>
> s = Session(e)
> s.add_all([
> B1(b_data='b11', b1='b1', a1='b11'),
> B2(b_data='b21', b2='b2', a1='b21', cs=[C(), C(), C()]),
> B3(b_data='b31', b3='b3', a1='b31'),
> B1(b_data='b12', b1='b1', a1='b12'),
> B1(b_data='b13', b1='b1', a1='b13'),
> B2(b_data='b22', b2='b2', a1='b22', cs=[C(), C()]),
> B3(b_data='b32', b3='b3', a1='b12'),
> B3(b_data='b33', b3='b3', a1='b33')
> ])
> s.commit()
>
>
> q = s.query(A).filter(A.a1.like('%2%'))
>
> result = q.all()
>
> print "----- no more SQL ----"
> for b in result:
> if isinstance(b, B1):
> print b.b1
> elif isinstance(b, B2):
> print b.cs
> print b.b2
> elif isinstance(b, B3):
> print b.b3
>
>
>
>
> On 04/04/2017 12:16 AM, da...@benchling.com wrote:
> > Hey Mike,
> >
> > Looks like I spoke too soon -- a few more questions:
> >
> > Using the example code you posted, we're actually seeing 4 additional
> > queries (one per result model), rather than the expected 3 (one per
> > result model type). If you print context.query inside load_extra, I
> > think it's clear why:
> >
> > - the loader sequentially processes loaded models
> > (https://github.com/zzzeek/sqlalchemy/blob/master/lib/sqlalc
> hemy/orm/loading.py#L75)
> > - on processing the first B2, it executes a query to load all B2's data
> > - when processing the results of this new query, it now processes the
> > second B2 record (under a new context)
> > - load_extra() gets called for the new B2 with a different context than
> > the first B2
> > - this now executes _loader_for_cls
> >
> > Note that if you don't call _loader_for_cls in load_extra, load_extra is
> > called for each record using the correct context.
> >
> > A related issue is that if you query directly for B2, it'll redundantly
> > execute _loader_for_cls.
> >
> > I think we could solve both of these issues by doing this instead:
> >
> > q = orig_query.with_entities(target_cls)
> > if q == orig_query:
> > return
> >
> > Unfortunately, the == operator doesn't work for comparing queries. Do
> > you have a way to compare query equality, or alternatively have a
> > solution to both of these issues?
> >
> > Could you also elaborate on what you meant by this comment?
> >
> > # store this strong reference so recs don't get lost while
> > # iterating
> >
> >
> > Thanks again for all your help,
> > Damon
> >
> > On Monday, April 3, 2017 at 6:42:17 PM UTC-7, da...@benchling.com
> wrote:
> >
> > Thanks a ton for your help, Mike!
> >
> > We played around with it and are pretty happy with your solution
> > using the load() event, so we'll be using that moving forward.
> >
> >
> > Damon
> >
> > On Wednesday, March 29, 2017 at 2:40:39 PM UTC-7, Mike Bayer wrote:
> >
> > I have a working version of both loading relationships via IN as
> > well as
> > loading joined inheritance subclasses via IN, including your
> > great idea
> > that extra eager loaders should continue to work for the
> subclass
> > loaders.
> >
> > I've only tested it with one scenario so far and both patches
> > have a
> > long way to go re: tests and documentation.
> >
> > the scratch test case is currently in the commit message for the
> > second
> > patch, which illustrates a base class + subclass load where both
> > classes
> > have an additional relationship. This is at
> > https://gerrit.sqlalchemy.org/#/c/359/
> > <https://gerrit.sqlalchemy.org/#/c/359/>, note this builds upon
> the
> > previous gerrit at https://gerrit.sqlalchemy.org/#/c/352/
> > <https://gerrit.sqlalchemy.org/#/c/352/>. The work
> > at the moment will likely fall down with any kind of surprises
> > but if
> > you wanted to start running it and finding those cases, that is
> > always
> > helpful.
> >
> > So far this looks promising as something that can be in 1.2 with
> > perhaps
> > some "EXPERIMENTAL" warnings surrounding it, but overall 1.2 was
> > lacking
> > a "killer ORM feature" so these two would be it.
> >
> >
> >
> > On 03/23/2017 06:02 PM, mike bayer wrote:
> > >
> > >
> > > On 03/23/2017 02:40 PM, mike bayer wrote:
> > >>
> > >>
> > >> On 03/23/2017 12:53 PM, da...@benchling.com wrote:
> > >>> Hey Mike,
> > >>>
> > >>> Thanks for the quick response!
> > >>>
> > >>> For developers that are pretty familiar with the SQLAlchemy
> > API, but not
> > >>> so much the internals, would implementing the subqueryloads
> to
> > >>> contribute to SA be a reasonable endeavor? Could you
> > ballpark how much
> > >>> time how long it might take for us to do it?
> > >>
> > >> I haven't looked at what this would take, but it would be
> > intricate and
> > >> also need a lot of tests that are not easy to write. Like,
> > if you
> > >> worked on it, you could probably get something working, but
> > then that
> > >> probably wouldn't be how it really needs to be because all
> > kinds of
> > >> things that are simple for simple cases don't work with the
> > vast amount
> > >> of edge cases which we have.
> > >
> > > I've created an issue for both a new relationship loader and
> an
> > > inheritance loader at the same time, since they will use very
> > similar
> > > paths, at https://bitbucket.org/zzzeek/sqlalchemy/issues/3944
> > <https://bitbucket.org/zzzeek/sqlalchemy/issues/3944>. A POC
> > > for the relationship loader so far looks to be very simple
> > (but then
> > > again all the loaders start out very simple...) and is at
> > > https://gerrit.sqlalchemy.org/352
> > <https://gerrit.sqlalchemy.org/352>. The same infrastructure
> and
> > > approach would also be used for the mapper inheritance loader,
> > which
> > > would be enabled via a mapper()-level flag, as well as
> > per-query using a
> > > new query option.
> > >
> > > I can't yet guarantee this will be a 1.2 thing, I'd have to
> > get some
> > > more momentum going w/ test cases and all that. In a 1.2
> > release it
> > > would also be a little bit experimental as new loading styles
> > usually
> > > have small issues coming up for months or years, as people try
> > more use
> > > cases.
> > >
> > >
> > >
> > >
> > >
> > >
> > >>
> > >> The routine that's loading the additional columns just for
> > one object at
> > >> a time is here:
> > >>
> > >>
> > https://github.com/zzzeek/sqlalchemy/blob/master/lib/sqlalch
> emy/orm/loading.py#L635
> > <https://github.com/zzzeek/sqlalchemy/blob/master/lib/sqlalc
> hemy/orm/loading.py#L635>
> >
> > >>
> > >> and then here for the bulk of it:
> > >>
> > https://github.com/zzzeek/sqlalchemy/blob/master/lib/sqlalch
> emy/orm/mapper.py#L2588
> > <https://github.com/zzzeek/sqlalchemy/blob/master/lib/sqlalc
> hemy/orm/mapper.py#L2588>
> >
> > >>
> > >>
> > >>
> > >> But the much harder part would be how to work this step into
> > the loading
> > >> infrastructure, which would be somewhere in
> > >>
> > https://github.com/zzzeek/sqlalchemy/blob/master/lib/sqlalch
> emy/orm/loading.py#L273
> > <https://github.com/zzzeek/sqlalchemy/blob/master/lib/sqlalc
> hemy/orm/loading.py#L273>,
> >
> > >>
> > >> which is a very intricate function with over a decade of
> > constant
> > >> refactorings behind it, and I'd have to think pretty deeply
> > for awhile
> > >> how best to do this.
> > >>
> > >> Not to mention that there's more than one way to do this
> > query, there's
> > >> either re-using the criteria from the original query, or
> there's
> > >> injecting the primary key ids of the whole list of objects
> > into an IN
> > >> clause after the fact. The latter approach is probably more
> > efficient
> > >> but wouldn't work for composite primary keys outside of
> > Postgresql. As
> > >> a built in feature I'd want "IN" loading to be an option at
> > least.
> > >>
> > >>
> > >>
> > >>>
> > >>> Regarding STI and relationships, is there any way to do that
> > but still
> > >>> get the benefits of JTI? e.g. is there an easy way to
> resolve
> > >>> my_base_class_inst.subclass_prop as a proxy to the
> subclass?
> > We could
> > >>> roll our own using __getitem__ but it seems a little hairy.
> > >>
> > >> So proxying to a related item wouldn't be terrible, sure you
> > could use
> > >> __getitem__ or you could also add descriptors to the primary
> > class,
> > >> adding the descriptors to match the "info" could be automated
> > as well
> > >> (or even do it in the other direction, add special descriptor
> > to main
> > >> class == a column gets added to related class).
> > >>
> > >>
> > >> Doing the thing where you query() for all the related classes
> > after the
> > >> fact yourself might not be that terrible. you can use the
> > load() event
> > >> which receives the query context that has the query you need
> > already. I
> > >> guess it's time for proof of concept. Here's that. You
> > can see at
> > >> the end we load all the "bs" without any per-object load.
> > >>
> > >> from sqlalchemy import *
> > >> from sqlalchemy.orm import *
> > >> from sqlalchemy.ext.declarative import declarative_base
> > >> from sqlalchemy import event
> > >>
> > >> Base = declarative_base()
> > >>
> > >>
> > >> class A(Base):
> > >> __tablename__ = 'a'
> > >> id = Column(Integer, primary_key=True)
> > >> a1 = Column(String)
> > >> type = Column(String)
> > >>
> > >> __mapper_args__ = {'polymorphic_on': type}
> > >>
> > >>
> > >> class B1(A):
> > >> __tablename__ = 'b1'
> > >> id = Column(Integer, ForeignKey('a.id <http://a.id>'),
> > primary_key=True)
> > >> b1 = Column(String)
> > >> b_data = Column(String)
> > >> __mapper_args__ = {'polymorphic_identity': 'b1'}
> > >>
> > >>
> > >> class B2(A):
> > >> __tablename__ = 'b2'
> > >> id = Column(Integer, ForeignKey('a.id <http://a.id>'),
> > primary_key=True)
> > >> b2 = Column(String)
> > >> b_data = Column(String)
> > >> cs = relationship("C", lazy='subquery')
> > >>
> > >> __mapper_args__ = {'polymorphic_identity': 'b2'}
> > >>
> > >>
> > >> class C(Base):
> > >> __tablename__ = 'c'
> > >> id = Column(Integer, primary_key=True)
> > >> b2_id = Column(ForeignKey('b2.id <http://b2.id>'))
> > >>
> > >>
> > >> class B3(A):
> > >> __tablename__ = 'b3'
> > >> id = Column(Integer, ForeignKey('a.id <http://a.id>'),
> > primary_key=True)
> > >> b3 = Column(String)
> > >> b_data = Column(String)
> > >> __mapper_args__ = {'polymorphic_identity': 'b3'}
> > >>
> > >>
> > >> def _loader_for_cls(target, context):
> > >> orig_query = context.query
> > >>
> > >> target_cls = type(target)
> > >>
> > >> # take the original query and chance the entity to the
> > subclass
> > >> q = orig_query.with_entities(target_cls)
> > >>
> > >> # defer everything that's not PK / polymorphic_on from A.
> > this whole
> > >> # bit is just to avoid all those extra columns
> > >> to_defer = []
> > >> mapper = inspect(target).mapper
> > >> inherited = mapper.inherits
> > >> while inherited is not None:
> > >> for attr in inherited.column_attrs:
> > >> if not attr.expression.primary_key and \
> > >> attr.expression is not
> > inherited.polymorphic_on:
> > >> to_defer.append(attr.key)
> > >> for attr in inherited.relationships:
> > >> to_defer.append(attr.key)
> > >> inherited = inherited.inherits
> > >> q = q.options(*[defer(k) for k in to_defer])
> > >>
> > >> # store this strong reference so recs don't get lost
> while
> > >> # iterating
> > >> return q.all()
> > >>
> > >>
> > >> @event.listens_for(A, "load", propagate=True)
> > >> def load_extra(target, context):
> > >> key = ('loader_by_cls', type(target))
> > >>
> > >> if key not in context.attributes:
> > >> context.attributes[key] = _loader_for_cls(target,
> > context)
> > >>
> > >>
> > >> e = create_engine("sqlite://", echo=True)
> > >> Base.metadata.create_all(e)
> > >>
> > >>
> > >> s = Session(e)
> > >> s.add_all([
> > >> B1(b_data='b11', b1='b1', a1='b11'),
> > >> B2(b_data='b21', b2='b2', a1='b21', cs=[C(), C(), C()]),
> > >> B3(b_data='b31', b3='b3', a1='b31'),
> > >> B1(b_data='b12', b1='b1', a1='b12'),
> > >> B1(b_data='b13', b1='b1', a1='b13'),
> > >> B2(b_data='b22', b2='b2', a1='b22', cs=[C(), C()]),
> > >> B3(b_data='b32', b3='b3', a1='b12'),
> > >> B3(b_data='b33', b3='b3', a1='b33')
> > >> ])
> > >> s.commit()
> > >>
> > >>
> > >> q = s.query(A).filter(A.a1.like('%2%'))
> > >>
> > >> result = q.all()
> > >>
> > >> print "----- no more SQL ----"
> > >> for b in result:
> > >> if isinstance(b, B1):
> > >> print b.b1
> > >> elif isinstance(b, B2):
> > >> print b.cs
> > >> print b.b2
> > >> elif isinstance(b, B3):
> > >> print b.b3
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>>
> > >>>
> > >>> Thanks again,
> > >>> Damon
> > >>>
> > >>> On Wednesday, March 22, 2017 at 3:59:45 PM UTC-7, Mike Bayer
> > wrote:
> > >>>
> > >>>
> > >>>
> > >>> On 03/22/2017 02:17 PM, da...@benchling.com
> > <javascript:> wrote:
> > >>> > Hey all,
> > >>> >
> > >>> > We were wondering if you had any advice on having a
> > large (~10)
> > >>> number
> > >>> > of polymorphic subclasses for a single base class.
> Using
> > >>> > with_polymorphic: '*' causes SQLAlchemy to joinedload
> all
> > >>> subclasses
> > >>> > like this:
> > >>> >
> > >>> > SELECT ...
> > >>> > FROM base_table
> > >>> > LEFT OUTER JOIN sub_table_1 ON base_table.id
> > <http://base_table.id>
> > >>> <http://base_table.id> = sub_table_1.id
> > <http://sub_table_1.id> <http://sub_table_1.id>
> > >>> > LEFT OUTER JOIN sub_table_2 ON base_table.id
> > <http://base_table.id>
> > >>> <http://base_table.id> = sub_table_2.id
> > <http://sub_table_2.id> <http://sub_table_2.id>
> > >>> > ...
> > >>> >
> > >>> > Postgres buckles under too many joins, and these
> > queries start
> > >>> taking a
> > >>> > really long time.
> > >>> >
> > >>> > One other note is that for most of our queries, only a
> > few of
> > >>> these
> > >>> > sub-tables are actually needed, so most of the joins
> > are wasted.
> > >>> > Unfortunately, ahead of time, we don't know which
> > tables will be
> > >>> needed
> > >>> > -- we're relying on the discriminator.
> > >>> >
> > >>> > Ideally, we'd be able to specify that the ORM should
> > >>> subqueryload the
> > >>> > subclasses (and only execute subqueries on the types
> > that are
> > >>> present).
> > >>> > This would have to happen both when querying the base
> > table, but
> > >>> also
> > >>> > when accessing relationships. We'd want it to execute
> > a query on
> > >>> the
> > >>> > base table, then execute one query for each present
> > subclass.
> > >>> >
> > >>> > Another solution might be to use some kind of hook
> that
> > >>> >
> > >>> > - is executed after a query returns with results (or
> > after a
> > >>> list of
> > >>> > models are added to the session?)
> > >>> > - groups the models by type and runs its own
> > subqueries to load
> > >>> the data
> > >>> >
> > >>> > Any help here is greatly appreciated!
> > >>>
> > >>>
> > >>> The purpose of with_polymorphic is more about being able
> to
> > >>> filter on
> > >>> multiple classes at the same time, which is why it uses
> > joins, but
> > >>> these
> > >>> don't scale to many subclasses. Adding a subquery
> > load for the
> > >>> related tables would be something that the ORM can
> > someday have as a
> > >>> feature, but it would need a lot of tests to ensure it's
> > working as
> > >>> advertised.
> > >>>
> > >>> There's a lot of ways to get those other tables loaded
> > but none of
> > >>> them
> > >>> look that great. Turning off with_polymorphic(), one
> > approach
> > >>> is to
> > >>> collect all the distinct types and identifiers from your
> > query
> > >>> result;
> > >>> then do a separate query for each subtype:
> > >>>
> > >>> result = session.query(BaseClass).filter(...).all()
>
> > >>>
> > >>> types = sorted([(type(obj), obj.id
> > <http://obj.id> <http://obj.id>) for obj
> > >>> in result],
> > >>> key=lambda t: t[0])
> > >>>
> > >>> for type, ids in itertools.groupby(types,
> > key=lambda t:
> > >>> t[0]):
> > >>>
> > session.query(type).filter(type.id.in_(ids)).all()
> > >>>
> > >>> That will emit a query with an INNER JOIN for each class
> > and will
> > >>> populate the remaining records in the identity map. The
> > columns
> > >>> that
> > >>> are already loaded are not re-accessed, though the DBAPI
> > will still
> > >>> send
> > >>> them over the network to the cursor. You can try
> > limiting the
> > >>> columns
> > >>> you query for in each statement as well by using the
> > defer() option.
> > >>>
> > >>> Another way is to use with_polymorphic() but to provide
> > a different
> > >>> kind
> > >>> of SQL statement, like a polymorphic_union(). This
> > would be a
> > >>> UNION of
> > >>> statements that each have an inner join. the resulting
> > SQL is a
> > >>> beast
> > >>> but it at least isn't using those left outer joins. I
> > think you
> > >>> can
> > >>> probably use sqlalchemy.orm.util.polymorphic_union()
> > directly to get
> > >>> this UNION statement built up automatically.
> > >>>
> > >>> Still another way is to reorganize the mappings to use
> > single-table
> > >>> inheritance and relationship() to link out to the
> > related table,
> > >>> then
> > >>> the normal "subqueryload" feature to load them as
> > relationships.
> > >>> Even
> > >>> though this way is ugly, I might use this (short of
> > implementing the
> > >>> related table subqueryload feature) just to make things
> > simple.
> > >>>
> > >>>
> > >>> Definitely a feature that should be added but that's not
> an
> > >>> immediate
> > >>> solution.
> > >>>
> > >>> >
> > >>> >
> > >>> > Thanks,
> > >>> > Damon
> > >>> >
> > >>> > --
> > >>> > SQLAlchemy -
> > >>> > The Python SQL Toolkit and Object Relational Mapper
> > >>> >
> > >>> > http://www.sqlalchemy.org/
> > >>> >
> > >>> > To post example code, please provide an MCVE: Minimal,
> > Complete,
> > >>> and
> > >>> > Verifiable Example. See
> > http://stackoverflow.com/help/mcve
> > <http://stackoverflow.com/help/mcve>
> > >>> <http://stackoverflow.com/help/mcve
> > <http://stackoverflow.com/help/mcve>> for a full
> > >>> > description.
> > >>> > ---
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> > >>> send
> > >>> > an email to sqlalchemy+...@googlegroups.com
> <javascript:>
> > >>> > <mailto:sqlalchemy+unsubscr...@googlegroups.com
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> > <https://groups.google.com/group/sqlalchemy>
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> > >>> > For more options, visit
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> > >>> <https://groups.google.com/d/optout
> > <https://groups.google.com/d/optout>>.
> > >>>
> > >>> --
> > >>> SQLAlchemy -
> > >>> The Python SQL Toolkit and Object Relational Mapper
> > >>>
> > >>> http://www.sqlalchemy.org/
> > >>>
> > >>> To post example code, please provide an MCVE: Minimal,
> > Complete, and
> > >>> Verifiable Example. See http://stackoverflow.com/help/mcve
> > <http://stackoverflow.com/help/mcve> for a full
> > >>> description.
> > >>> ---
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> > >>> For more options, visit https://groups.google.com/d/optout
> > <https://groups.google.com/d/optout>.
> >
> > --
> > SQLAlchemy -
> > The Python SQL Toolkit and Object Relational Mapper
> >
> > http://www.sqlalchemy.org/
> >
> > To post example code, please provide an MCVE: Minimal, Complete, and
> > Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> > description.
> > ---
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>
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and
Verifiable Example. See http://stackoverflow.com/help/mcve for a full
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The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
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