Ok, that is clear now. Eagerloading of tables occurring more than once in a query is a bit confusing for me as it is not well-documented, for example that *contains_eager()* needs *alias=<parameter>* in order to work properly for a second occurrence of a table. If I might I would advise you to shed some light on the usage in a documentation.
OK, moving on When using .join(relation, aliased=True) it is stated that next *.fliter() *call will refer to the second occurrence (unless *.reset_joinpoint() *is called). Here <https://gist.github.com/ojomio/08e5d91d8eed6cc76a2c> I have an example of similar behavior. Consider my slightly modified example. it seems *contains_eager()*, when given not the full path from the first occurrence(B-A-A-B-C) but rather only the portion of path from the last mention of table(B-C), populates the collection with the data from the *latest* mentioned instance of that table Is it the desired outcome or should it be considered a bug? Could this pattern change in future? And, as always, thank you for you patience and attention brought to my problem среда, 15 июля 2015 г., 22:32:42 UTC+5 пользователь Michael Bayer написал: > > > > On 7/15/15 2:42 AM, Юрий Пайков wrote: > > I have an example here https://gist.github.com/ojomio/aa5eca3bea03d21e00e8. > This code issue exactly one query and load everything at one time > What I am asking about is line > https://gist.github.com/ojomio/aa5eca3bea03d21e00e8#file-gistfile1-py-L65 > > If I don not use alias *second_B* and simply write > > ).join( > AWithChildren.bs > ).options( > contains_eager(B.as_). > contains_eager(A.children, alias=AWithChildren). > contains_eager(AWithChildren.bs). > joinedload(B.cs) > ) > > > Then SQLAlchemy issue another query on *C* table, apparently not > matching expression AWithChildren.bs and B > So my question is - if there are many other tables after *A.children -* > should use alias() for every one and mention them like > .joinedload( PreviousTable.relation, alias=SomeTableAlias ). > ? > > > the use here of .joinedload() on the end of a series of contains_eager() > calls is already very unusual, and I'm somewhat surprised it works > correctly in the first case as this is not a use case that's really > tested. As for the case of second_b not being present, this is not > surprising as AWithChildren.bs refers to "B", which is already present in > the query as the primary entity, for a separate collection of B to be > present it needs to be aliased. the join(AWithChildren.bs) is the same as > join(B, AWithChildren.bs), and you'd never want to say what is essentially > session.query(B).join(Q).join(B) - you need an alias for each subsequent > occurrence of B. > > > > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+...@googlegroups.com <javascript:>. > To post to this group, send email to sqlal...@googlegroups.com > <javascript:>. > Visit this group at http://groups.google.com/group/sqlalchemy. > For more options, visit https://groups.google.com/d/optout. > > > -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
