2 days trying by myself... 20 minutes with your answer... I still don't know why I didn't try what you said...
Thank you, Michael 2012/5/16 Michael Bayer <mike...@zzzcomputing.com>: > > On May 16, 2012, at 5:50 PM, Hector Blanco wrote: > >> Hello everybody! >> >> I would like to know if it's possible to create an optimized query >> that gives all the elements of a class A that have a relationship to >> an specific class B > > from the below it seems like you mean "a specific *instance* B"... > >> As you can see, the Regions don't have a backref to Layout (mainly >> because they may be used in other classes) but one specific region >> will only be in one layout at the same time (regions are never shared >> by layouts) and one Region will never be used in the same layout more >> than once (there won't be a Layout.logoRegion and a >> Layout.mainImageRegion pointing to the same Region instance) >> >> What I would like to do is knowing what layouts (or, better said, >> "layout") are using an specific given region in any of its fields. >> >> Let's say, given this: >> >> Layouts: >> >> +----+-------+--------+----------------+----------------------+----------------------+ >> | id | width | height | logo_region_id | background_region_id | >> main_image_region_id | >> +----+-------+--------+----------------+----------------------+----------------------+ >> | 38 | 1280 | 720 | 8 | 7 | >> 9 | >> | 45 | 1280 | 720 | 15 | 16 | >> 17 | >> | 52 | 1280 | 720 | 23 | 24 | >> 25 | >> +----+-------+--------+----------------+----------------------+----------------------+ >> >> >> I would like to have a method to say "What layouts are using region >> '16'?" > > so say you have region 16 - "what layouts"? query for layouts: > > region = s.query(Region).get(16) > s.query(Layout).filter(or_( > Layout.logoRegion==region, > Layout.mainImageRegion==region, > Layout.backgroundRegion==region > )) > > basically SomeClass.some_m2o_relationship==some_instance will pull out the PK > of some_instance and compare it to the FK column on SomeClass. > > If you had the numerical id of some_instance instead, you'd adjust this to > compare on the column, not the relationship. > > this would be perfect for a class method also: > > class Layout(...): > .... > > @classmethod > def has_region(cls, some_region): > return or_( > Layout.logoRegion==region, > Layout.mainImageRegion==region, > Layout.backgroundRegion==region > ) > > s.query(Layout).filter(Layout.has_region(some_region)) > > > > -- > 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. > -- 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.
