Hi list!
I am facing a little problem whose I'm sure has a very simple
solution, but I haven't been able to find it (the solution, I mean)...
I would like to be able to pass the fields (relationships) I want to
pre-load as a parameter. Let's say I have a couple of classes:
-------------------------------------------------
class ElementsGroup(declarativeBase):
"""Represents a group of elements"""
__tablename__ = "elements_groups"
_id = Column("id", Integer, primary_key=True)
elements = relationship("Element" ... , collection_class=set )
elementGroups = relationship("ElementGroup", ... ,
collection_class=set)
-------------------------------------------------
And then the "Element" class:
-------------------------------------------------
class Element(declarativeBase):
__tablename__ = "elements"
_id = Column("id", Integer, primary_key=True)
otherThings = relationship("Things", ... , collection_class=set)
-------------------------------------------------
I would like to create a method to load objects of "ElementsGroups"
that would accept a parameter containing which relationships have to
be pre-loaded with a joinedload. Something like:
-------------------------------------------------
class ElementsGroupManager(object):
@staticmethod
def getAll(relationshipsToPreLoad=list()):
retval = list
try:
if (relationshipsToPreLoad):
retval =
Database.session.query(ElementsGroup.ElementsGroup).options(joinedload_all(relationshipsToPreLoad)).all()
else:
retval =
Database.session.query(ElementsGroup.ElementsGroup).all()
finally:
Database.session.close()
return retval
-------------------------------------------------
And in relationshipsToPreload I can say, for instance:
["elements", "elements.otherThings"]
(and would preload ElementsGroup.elements and the "otherThings" field
of each "element" object in the ElementsGroup.elements
list/relationship)
or
["elementGroups"]
which would just pre-load ElementsGroups.elementGroups (and not the
ElementsGroups.elements)
I'm sure it's very easy, but I haven't been able to do it... If I try
to pass relationshipsToPreLoad=['elements', 'elementGroups'] I get
something like:
> Mapper 'Mapper|Element|elements' has no property 'elementGroups'
It looks like it's trying to load (correctly) ElementsGroups.elements
but then it's trying to load ElementsGroups.elements.elementGroups
(which is not what I want... I want to load
ElementsGroups.elementGroups)
Thanks in advance!
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