SQLAlchemy generates wrong SELECTs for classes that are mapped to
select expressions. Consider the following example:
from sqlalchemy import *
metadata = MetaData("...", echo=True)
table = Table("test", metadata,
Column("id", Integer, primary_key=True),
Column("data", String))
table.create()
table.insert().execute([{"data": 1}, {"data": 2}])
test = table.select(table.c.id != 1).alias("test")
class Test(object):
pass
mapper(Test, test)
referer = Table("referer", metadata,
Column("id", Integer, primary_key=True),
Column("fk", Integer, ForeignKey("test.id")))
referer.create()
referer.insert().execute([{"fk": 2}])
class Referer(object):
pass
mapper(Referer, referer, properties={"ref": relation(Test)})
session = create_session()
t = session.query(Test).get(2)
print t
r = session.query(Referer).get(1)
print r.fk, r.ref
This prints among others:
SELECT test.data AS test_data, test.id AS test_id
FROM (SELECT test.id AS id, test.data AS data
FROM test
WHERE test.id != %(test_id)s) AS test
WHERE test.id = %(test_id_1)s ORDER BY test.id
2007-10-16 15:37:21,817 INFO sqlalchemy.engine.base.Engine.0x..34
{'test_id_1': None, 'test_id': 2}
SELECT referer.fk AS referer_fk, referer.id AS referer_id
FROM referer
WHERE referer.id = %(referer_id)s ORDER BY referer.id
{'referer_id': 1}
SELECT test.data AS test_data, test.id AS test_id
FROM (SELECT test.id AS id, test.data AS data
FROM test
WHERE test.id != %(test_id)s) AS test
WHERE test.id = %(test_id_1)s ORDER BY test.id
{'test_id_1': None, 'test_id': 2}
The first nested SELECT is wrong: test_id should be 1 and test_id_1
should be 2. The same holds for the third SELECT that tries to follow
the foreign key.
Therefore, the program prints
None
2 None
Best regards
Klaus
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