using python 2.7, sqla 0.7.9, postgresql 9.1
i'm trying to eager load a relationship to a polymorphic target (the target
uses joined table inheritance).
here is example:
http://pastebin.com/xSiHS4QW
and this is output:
SELECT
...
FROM container
LEFT OUTER JOIN root AS root_1 ON root_1.id = container.root_id
no type1, not type2?
looks like with_polymorphic mappig arg controls that:
http://pastebin.com/FfmJSZWc
and this is output:
SELECT ...
FROM container
LEFT OUTER JOIN (
SELECT ...
FROM root
LEFT OUTER JOIN type1 ON root.id = type1.id
LEFT OUTER JOIN type2 ON root.id = type2.id
) AS anon_1 ON anon_1.root_id = container.root_id
but i thought i'd get:
SELECT ...
FROM container
LEFT OUTER JOIN root AS root_1 ON root_1.id = container.root_id
LEFT OUTER JOIN type1 ON root.id = type1.id
LEFT OUTER JOIN type2 ON root.id = type2.id
this is not problem for small sets but for bulk ops either lazy loading or
subselect are much slower.
it looks like many have run into this. i tried using contains_eager but
though
that joins how i want it still does not load the entire target object (just
base):
c = Container
.query
.join(Container.root)
.outerjoin(type1, root.c.id == type1.c.id)
.outerjoin(type2, root.c.id == type2.c.id)
.options(contains_eager(Container.root))
.first()
c.root.field2 # field2 was not mapped so will do SELECT
is there a way to build a query that eagerly loads the whole entity?
q = Session.query ...
c = q.first()
c.root.field2 # already loaded so not SELECT
thanks
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