A new problem, which seems to occur in both IronPython and normal Python:
I have a database with tables for movies, directors, genres (and a
bridging table movie_directors)
I have a class mapped to a join of all three of the above
>>>
j = join(movies_table,md_table).join(directors_table).join(genres_table)
mapper(MoviesAndDirectorsAndGenres,j.select(use_labels=True).alias('moviesdirectorsgenres'))
this works fine. i can query the database ok using this mapper.
The tables already have some values in.
Now, I want to create a new composite object, that references some of
the existing values, but not all - say it's a new movie by an existing
director in an existing genre:
>>>
new = MoviesAndDirectorsAndGenres()
new.movies_movie_id=8 #does not already exist in the table
new.directors_director_id=2 #already exists in the table
new.genres_genre_id=6 #already exists too
session.add(new)
this fails with a constraint error / integrity error, because SQLA
tries to re-insert genre #6 even though it already exists. it also
happens if i use session.merge(new). it also happens if i fully
specify all of the attributes of each movie/director/genre correctly.
Is this expected behaviour? is there any way to get sqla to
intelligently only do inserts when necessary? is it something to do
with cascade configuration, and if so, how do i configure cascades on
a mapper that's not based on relationship() but based on join()?
thanks in advance!
HP
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