So FWIW, for now, I cast all three columns into strings and concatenated them using the column_property() expression in the mapper, and then did the comparison on that. It worked ok to create the join condition I needed. It wasn't a pretty as a tuple comparison but it got the job done and I can hit my deadline for tomorrow morning.
On Sunday, April 20, 2014 2:38:21 PM UTC-4, Rick Otten wrote: > > I would like to apply a condition in an outer join that matches a > multi-item list rather than a single value. > > In other words, I'm trying to get SQLAlchemy 0.8.6 connecting to > PostgreSQL 9.3.4 to generate SQL like this: > > > > select >> * >> from >> mytable mt >> left outer join myothertable mo on >> (m0.col1, m0.col2, mo.col3) = (select m2.col1, m2.col2, m2.col3 >> from >> myothertable m2 >> where mt.col1 = >> m2.wilson_id >> order by m2.col3 >> desc >> limit 1) > > > > When I construct my query object back in Python 2.7: > mo = aliased(myothertable) > m2 = aliased(myothertable) > mySession.query(mytable, myothertable)\ > .select_from(mytable)\ > .outerjoin(mo, > [mo.col1, mo.col2, mo.col3] == select(\ > [m2.col1, m2.col2, m2.col3])\ > .where(m2.col1 == mytable.col1)\ > .order_by(m2.col3.desc())\ > .limit(1)) > > > I get: > > File "build/bdist.linux-x86_64/egg/sqlalchemy/orm/query.py", line 1699, > in outerjoin > File "<string>", line 1, in <lambda> > File "build/bdist.linux-x86_64/egg/sqlalchemy/orm/query.py", line 51, in > generate > File "build/bdist.linux-x86_64/egg/sqlalchemy/orm/query.py", line 1816, > in _join > File "build/bdist.linux-x86_64/egg/sqlalchemy/orm/query.py", line 1846, > in _join_left_to_right > File "build/bdist.linux-x86_64/egg/sqlalchemy/orm/query.py", line 1861, > in _prepare_right_side > File "build/bdist.linux-x86_64/egg/sqlalchemy/inspection.py", line 74, > in inspect > *sqlalchemy.exc.NoInspectionAvailable: No inspection system is available > for object of type <type 'bool'>* > > > I tried both List type and Tuple type in my comparison from the inner > select statement. > When I look at the code where this exception is thrown, it suggests that > something is wrong with my mapping. > > I've done this join by comparing a single column with these two tables, > and I've done similar things with other single column comparisons. I'm not > sure why I'm unable to compare a set of columns instead. > > I've been pondering casting all three columns to string and then > concatenating them (either in the table mapping, or in the query) to see if > I can get back to a single value comparision which I expect to work. I'd > rather just compare the tuple/lists though. > > I could use some hints. If you guys have some. Thanks! > > > > > -- 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.
