On Nov 23, 2012, at 3:38 AM, Martin84 wrote: > Hi Diana & Michael Bayer, > > thanks for your help! > So, you both use sqlalchemy 0.8 and I use 0.7.9 and that explains our > different SQL queries. > Now, with the join_depth=1 parameter the unexplainable SQL queries disappear > and there is no more difference between lazy='subquery' and subqueryload(). > But unfortunately now there is an other and far more problematic issue, the > output of showDatabase is incorrect. > > I modify my showDatabase() function like this: > > def showDatabase(session): > house = session.query(House).one() > for resident in house.residents: > print resident.myChildren > > and now only one resident have a children (the men), and the one from the > woman disappear! > How is this possible? > > Here is my complete script with output: http://pastebin.com/HRqSWxQ0
Child refers to its parent via id_human, is a many-to-one - a Child can only have *one* human. your script assigns newChild twice, once to newMen, once to newWoman. assigning it to newWoman essentially removes it from newMen. > > Am Freitag, 23. November 2012 06:43:33 UTC+1 schrieb Michael Bayer: > > On Nov 22, 2012, at 11:16 AM, Martin84 wrote: > >> Hi Diana & Michael Bayer, >> >> you both have exactly the same results/sql queries, but unfortunately my >> results are different. This is really strange, >> here is my complete python script with my output: >> http://pastebin.com/CyCs90cW > > As a side note, that script is slightly different. A "lazy='joined'" is > added to Human.houses. So after your session.close(), then your > query(Woman), you get "human JOIN woman" which is the query(Woman), then it > also has "LEFT OUTER JOIN human_house_table LEFT OUTER JOIN house", which is > your Human.houses lazy="joined". I'd usually not use "lazy" at all in a > joined inheritance mapping, as there are already too many JOINs happening > implicitly for there to be extra joins like this coming in. > > So then, why you don't see the "subquery". In 0.7, you need join_depth=1 > here, because otherwise, the ORM sees Woman->Child as Human->Human, which is > a cycle. join_depth=1 means, "it's OK to join one time in this cycle". > > In 0.8 this was improved so that Woman->Child isn't seen as a cycle, the > subclass identity is taken into account - so join_depth can be removed. See > http://www.sqlalchemy.org/trac/ticket/2481 for a description of this issue. > > Overall, 0.8 has a lot of improvements to joined inheritance in conjunction > with eagerloading and with_polymorphic. > > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To view this discussion on the web visit > https://groups.google.com/d/msg/sqlalchemy/-/OUUgp8S57XAJ. > To post to this group, send email to sqlalchemy@googlegroups.com. > To unsubscribe from this group, send email to > sqlalchemy+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/sqlalchemy?hl=en. -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
