Very good! Thank you! On Wednesday, January 15, 2014 1:17:56 PM UTC-5, Michael Bayer wrote: > > > On Jan 15, 2014, at 12:58 PM, Matt Schmidt <slo...@gmail.com <javascript:>> > wrote: > > So here's a simplified version of the models I have: > http://pastie.org/private/smqzkvz4zj46skfmipruw > Python==3.3 > SQLAlchemy==0.9.1 > psycopg2==2.5.2 > Postgresql 9.2 > > Running the following query, > session.query(Training).filter(Training.start_date > '2013-11-01') > > Gives me the following SQL: > SELECT trainings.id AS trainings_id, trainings.title AS trainings_title, > view_training_start_dates_1.start AS view_training_start_dates_1_start > FROM view_training_start_dates, trainings LEFT OUTER JOIN > view_training_start_dates AS view_training_start_dates_1 ON trainings.id= > view_training_start_dates_1.training_id > WHERE view_training_start_dates.start > '2013-11-01' > > There are two problems. In the FROM clause, view_training_start_dates > should not be there, and in the WHERE clause, > `view_training_start_dates.start` should be > `view_training_start_dates_1.start`. > > Is what I'm trying possible with hybrid properties? Or should I be looking > to alter the query instead? > > Note: I tried doing a simple select expression for start_date, but it > wasn't performing as well as I'd like. > > > > the issue here is that when you say > “query(Training).filter(Training.start_date > date)", that is shorthand for > "query(Training).filter(ViewTrainingStartDates.start > date)”. That is, > it’s as though you wrote “SELECT * FROM table1, table2” without using JOIN, > hence your statement has “FROM view_training_start_dates, trainings” in it. > The “LEFT OUTER JOIN” is an entirely separate thing that is a result of > the lazy=“joined” (e.g. the eager load) on Training.training_start_date and > does not affect rows matched. The “view_training_start_dates_1” table is > part of the eager load and is not accessible to the Query in any other way > (see below). > > So when you say "query(A).filter(B.x > y)”, you need to JOIN, that is, > "query(A).join(A.bs).filter(B.x > y)”. > > Background on this technique specific to the usage of hybrid attributes is > at: > > > http://docs.sqlalchemy.org/en/rel_0_9/orm/extensions/hybrid.html#join-dependent-relationship-hybrid > . > > As far as what the LEFT OUTER JOIN is all about and why you can’t touch > any of those columns directly, see: > > > http://docs.sqlalchemy.org/en/rel_0_9/faq.html#i-m-using-joinedload-or-lazy-false-to-create-a-join-outer-join-and-sqlalchemy-is-not-constructing-the-correct-query-when-i-try-to-add-a-where-order-by-limit-etc-which-relies-upon-the-outer-join > > > which will then lead you to > http://docs.sqlalchemy.org/en/rel_0_9/orm/loading.html as well as > http://docs.sqlalchemy.org/en/rel_0_9/orm/loading.html#the-zen-of-eager-loading > . > > >
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