On Apr 19, 2011, at 9:04 AM, Kent wrote:
> I'm getting an SAWarning (0.6.4 and also 0.7b5dev) which has a message
> that confuses me, so I've duplicated the problem with a script:
> ===================================================
>
> mapper(PostSpotLight, spotlights_table,
> properties = {'postkeywords':
> relationship(Keyword, secondary=post_keywords,
>
> primaryjoin=spotlights_table.c.post_id==post_keywords.c.post_id)}
> )
>
> [...]/sqlalchemy-default/lib/sqlalchemy/orm/properties.py:900:
> SAWarning: No ForeignKey objects were present in secondary table
> 'post_keywords'. Assumed referenced foreign key columns
> 'post_keywords.keyword_id', 'post_keywords.post_id' for join condition
> 'spotlights.post_id = post_keywords.post_id' on relationship
> PostSpotLight.postkeywords
> eq_pairs = self._sync_pairs_from_join(self.primaryjoin, True)
>
> Why is the complaint that there are No ForeignKey objects were present
> in secondary table 'post_keywords', when clearly there are?
Well this is the message knowing something was wrong but not expressing it in a
way that I expected when I wrote it. post_keywords has no foreign keys that
refer to the "spotlights" table. if a primaryjoin condition is given, it
only cares about foreign keys that express components of the join condition.
this used to be an error condition but eventually I figured that things would
just "work" if I assumed the cols in post_keywords were FKs, after I saw
someone confused by placing a "secondary" table that in fact had no FKs on it.
>
> ***Furthermore, if I pass the relationship this:
>
> foreign_keys=[post_keywords.c.post_id,post_keywords.c.keyword_id]
>
> then the warning goes away, but all I've done is specify the very
> foreign_keys that already exist.***
well in this case you give it some columns, but not what they reference to. So
it sees "post_id" and it says, oh, thats the FK that points to
spotlights.post_id.
--
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.
