Yes, 'number' is a column, as you surmised. When I drop that from the path
it works fine. The only remaining problem is/was that this ends up loading
in every field in the child_product table, and this includes a potentially
massive BSON column (and more).
After looking into this, I've now learned about deferred, defer, undefer,
loadonly, etc. This seems to be the correct way to manage this, and it
appears to be working fine:
q = q.options(sa.orm
.joinedload("defined_items")
.joinedload("child_product")
.load_only("number")
)
Thanks for pointing me in the right direction! This page had the info I
needed:
http://docs.sqlalchemy.org/en/latest/orm/loading_columns.html
Russ
On Thursday, May 21, 2015 at 4:01:16 PM UTC-4, Michael Bayer wrote:
>
>
>
> On 5/21/15 3:56 PM, Russ wrote:
>
> nope. I'd need a complete, self-contained and succinct example I can
>> run, thanks
>>
>
> Ok, thanks. This is a beefy one so that will be extremely tricky to
> extract. I had hoped that the combo of lazy+joined would have been a clear
> indicator since they are opposite loading strategies.
>
>
> the word "lazy" there is the name of the field. It is the internal
> equivalent to the "lazy" argument on relationship:
>
>
> http://docs.sqlalchemy.org/en/rel_1_0/orm/relationship_api.html?highlight=relationship#sqlalchemy.orm.relationship.params.lazy
>
> that said, here is exactly what will cause your error. Any of the
> attribute names "defined_items", "child_product" or "number" are not in
> fact bound to a relationship(), and instead refer to a Column-mapped
> attribute. Looks a lot like "number" here is a Column. Is that the case?
> You can't call joinedload for a column attribute.
>
>
>
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