"C"/"D" objects doesn't exist without "A" and "B"? maybe walk up the graph: C.b.a.type
im not sure this schema is sensible, if it's really bad, please advise, im not attached to it! thax! On Wed, May 5, 2010 at 5:28 PM, Michael Bayer <[email protected]>wrote: > what query do you want to see when you select "C" and "D" objects ? > > > > On May 5, 2010, at 5:26 PM, Timmy Chan wrote: > > thx, is there a way to set that up, or something similar? > > after giving it thought, maybe polymorphic_on isn't what i need. in some > sense, table "A" is similar to a generic container, and i want to constrain > the type of "C" depending on "A"'s type column. is there a way to do this? > > On Wed, May 5, 2010 at 5:15 PM, Michael Bayer <[email protected]>wrote: > >> >> On May 5, 2010, at 5:01 PM, Timmy Chan wrote: >> >> i have 4 tables, a, b, c, d. >> >> a has one-to-many relation with b, b with one-to-one relationship with c, >> c is a polymorphic on a.type, with d being one of the polymorphic types. >> >> is there a way to implement this? >> >> details: >> >> this is what im trying to do in sqlalchemy: >> >> a = Table('a', metadata, >> Column( 'id', Integer(), primary_key=True ), >> Column( 'type', UnicodeText() ) ) >> >> b = Table('b', metadata, >> Column( 'id', Integer(), primary_key=True ), >> Column( 'a_id', Integer(), ForeignKey('a.id') ) ) >> >> c = Table('c', metadata, >> Column( 'id', Integer(), primary_key=True ), >> Column( 'b_id', Integer(), ForeignKey('b.id') ), >> Column( 'class_id', Integer() ) ) >> >> d = Table('d', metadata, >> Column( 'id', Integer(), primary_key=True ), >> Column( 'data', Integer() ) >> >> mappers >> >> mapper( A, a ) >> mapper( B, b, properties={'a': relationship( A, >> uselist=False,backref='b', >> 'c':relationship( C, uselist=False, backref='b') }) >> >> # Does a full join, does not work >> mapper( C, c, polymorphic_on = a.c.type ) >> mapper( D, d, inherits=C, polymorphic_identity = "D" ) >> >> >> how can i change c to polymorphic on a, through the relationship? is >> there a way to sort by d.data? (b-c/d is one-on-one). >> >> >> this mapping is incorrect. mapper(C) cannot be polymorphic on a table >> which is not part of its mapping, and mapper(C) does not contain an >> "inherits" keyword to that of A. Usually the "polymorphic_on" setting is >> on the base-most mapper in the hierarchy and its not clear here which mapper >> you intend for that to be. >> >> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "sqlalchemy" group. >> To post to this group, send email to [email protected]. >> To unsubscribe from this group, send email to >> [email protected]<sqlalchemy%[email protected]> >> . >> 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 [email protected]. > To unsubscribe from this group, send email to > [email protected]. > 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 [email protected]. > To unsubscribe from this group, send email to > [email protected]<sqlalchemy%[email protected]> > . > 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 [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
