On Apr 7, 2008, at 4:54 PM, Tim Lesher wrote:
>
> I'm having some trouble using the has() operator to avoid a long chain
> of joins in a select.
>
>
> session
> .query(Action).filter(Action.task.has(Connection.caller==caller1))
>
> However, this appears to generate a cartesian join on the 'tasks' and
> 'connections' in the EXISTS() subselect, which leads to extra actions
> being returned.
for this kind of thing, you're joining across three tables, so you can
put an extra join condition in the has():
filter(Action.task.has(and_(Connection.caller==caller1,
Task.connection_id==Connection.id)))
or do it with join():
query(Action).join('task').filter(Task.has(Connection.caller==caller1))
I have an intuitive sense that there should be some nice syntax to get
has() and any() to join across more tables but its not occuring to me
at the moment.
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