On Jan 11, 2008, at 10:03 AM, Alexandre Conrad wrote:
> > svilen wrote: >> On Friday 11 January 2008 16:12:08 Alexandre Conrad wrote: >> >>> Channel -> Playlist -> Media >>> Channel -> CatalogChannel(Catalog) -> Media >>> >>> (Media has a fk to Catalog, not CatalogChannel) >>> The only element I have, is "playlist" (instance of Playlist). At >>> this point, I need to find out the available Media of the >>> Playlist's Channel's catalog so I can attach them to the Playlist. >>> >>> At first, I tryied out: >>> >>> Media.query.join(["catalog", >>> "channel"]).filter(Channel.c.id==playlist.id_channel).all() >>> >>> But then it complains that "channel" is not part of the Catalog >>> mapper. Catalog ? I want it to be looking at CatalogChannel, this >>> is the one having the "channel" relation, not Catalog. >> >> i see what u want, but formally (computer languages are formal, SA is >> a language) u are contradicting yourself. u said above that >> media points to catalog and not to catalogchannel. How u expect it to >> find a .channel there? > > I was expecting that SA would know that from the polymorphic "type" > flag. I have a "catalog" relation on media. When I do media.catalog, > it > doesn't just return a Catalog object, but really a CatalogChannel > object > (which is the whole point of polymorphic inheritance). And I thought > it > could figure out channel from that. But Mike said no. :) That's why he > talked about having some extra API query methods: I dont see where the "type" element youre mentioning is present in this query. if Media points to Catalog, thats the end of the story - what is telling it about a "CatalogChannel" ? look at it this way. Suppose you have CatalogA(Catalog), CatalogB(Catalog), CatalogChannel(Catalog), CatalogQ(Catalog). all four of those classes have an attribute called "channel". Catalog does not. Media references Catalog; therefore, the "catalog" attribute on Media can be any of: CatalogA, CatalogB, CatalogChannel, Catalog, or CatalogQ. Now I say: Media.query.join(["catalog", "channel"]) Whats the join is has to produce ? what table does it join to ? catalog_channel, catalog_a, catalog_b, catalog_c, catalog_q ? or does it try to make a UNION out of joins for all of those (clearly we arent going to guess that deeply) ? --~--~---------~--~----~------------~-------~--~----~ 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 [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~----------~----~----~----~------~----~------~--~---
