Sqlalchemy exists with joined inheritance and Firebird

Question

I tried to use sqlaclhemy joined table inheritance and had a strange occurrence.

class CommonObject(Base):
    __tablename__ = "objects"
    id = Column("objid", Integer, primary_key=True)
    objname = Column(String(32))
    ...    

class GoodsPlacement(Container, Loadable, Dumpable):
    __tablename__ = "goods_placements"
    id = Column("objid", Integer, ForeignKey("containers.objid"), primary_key=True)
    ...

class Departure(CommonObject):
     __tablename__ = "departures"
    id = Column(Integer, ForeignKey("objects.objid"),  primary_key=True)
    content_id = Column(Integer, ForeignKey("goods_placements.objid"))
    content = relationship("GoodsPlacement",
        primaryjoin="Departure.content_id==GoodsPlacement.id",
        foreign_keys=[content_id],
        lazy='joined',
        backref="departures")
    ...

When I write query:

session.query(GoodsPlacement).filter(~GoodsPlacement.departures.any(Departure.status_id < 2))

it generates me something like this:

SELECT 
    objects.objid AS objects_objid,
    goods_placements.objid AS goods_placements_objid,
    objects.objname AS objects_objname 
FROM objects
JOIN goods_placements ON objects.objid = goods_placements.objid 
WHERE NOT (EXISTS (
    SELECT 1 
    FROM (
        SELECT
            objects.objid AS objects_objid,
            objects.objname AS objects_objname,
            departures.id AS departures_id,
            departures.content_id AS departures_content_id,
            departures.status_id AS departures_status_id 
        FROM objects
        JOIN departures ON objects.objid = departures.id)
    AS anon_1, objects 
    WHERE anon_1.departures_content_id = objects.objid
        AND anon_1.departures_status_id < :status_id_1)
)

And this doesn't work because objects in exist clause overrides outer objects. As workaround I used exists from sqlexpression directly,

session.query(GoodsPlacement).filter(~exists([1],
    and_("departures.status_id<2",
         "departures.content_id=goods_placements.objid"),
    from_obj="departures"))

but it strongly depends from column and table names.

How I can specify alias for object table in exists statement?

Debian wheezy, python-2.7.3rc2, sqlaclhemy 0.7.7-1

Can you please add also the rest of the `query` definition, and not just `filter` part. — van, May 22 '12 at 11:01
these mappings are not complete. Is GoodsPlacement a subclass of CommonObject ? Can you please formulate a complete reproducing example (not including things that aren't relevant to the mis-produced query) and email the SQLAlchemy list please. generic relationships between joined-table inheriting mappers are extremely complicated. — zzzeek, May 23 '12 at 15:50
tickets have been added http://www.sqlalchemy.org/trac/ticket/2491 and http://www.sqlalchemy.org/trac/ticket/2492. the bug will likely not be fixed until 0.8 where the mechanics of any() have been improved. — zzzeek, May 23 '12 at 16:08

score 1 · Accepted Answer · edited Nov 01 '13 at 18:20

there's a bug involving the declarative system in how it sets up columns. The "objid" name you're giving the columns, distinct from the "id" attribute name, is the source of the issue here. The below test case approximates your above system and shows a workaround until the bug is fixed:

from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base

Base= declarative_base()

class CommonObject(Base):
    __tablename__ = "objects"
    id = Column("objid", Integer, primary_key=True)
    objname = Column(String(32))

class Container(CommonObject):
    __tablename__ = 'containers'
    id = Column("objid", Integer, ForeignKey("objects.objid"),  primary_key=True)

class GoodsPlacement(Container):
    __tablename__ = "goods_placements"
    id = Column("objid", Integer, ForeignKey("containers.objid"), primary_key=True)


class Departure(CommonObject):
    __tablename__ = "departures"
    id = Column(Integer, ForeignKey("objects.objid"),  primary_key=True)
    content_id = Column(Integer, ForeignKey("goods_placements.objid"))
    status_id = Column(Integer)
    content = relationship("GoodsPlacement",
        primaryjoin=lambda:Departure.__table__.c.content_id==GoodsPlacement.__table__.c.objid,
        backref="departures"
        )

session = Session()
print session.query(GoodsPlacement).filter(~GoodsPlacement.departures.any(Departure.status_id < 2))

output:

SELECT objects.objid AS objects_objid, containers.objid AS containers_objid, goods_placements.objid AS goods_placements_objid, objects.objname AS objects_objname 
FROM objects JOIN containers ON objects.objid = containers.objid JOIN goods_placements ON containers.objid = goods_placements.objid 
WHERE NOT (EXISTS (SELECT 1 
FROM (SELECT objects.objid AS objects_objid, objects.objname AS objects_objname, departures.id AS departures_id, departures.content_id AS departures_content_id, departures.status_id AS departures_status_id 
FROM objects JOIN departures ON objects.objid = departures.id) AS anon_1 
WHERE anon_1.departures_content_id = goods_placements.objid AND anon_1.departures_status_id < :status_id_1))

Sqlalchemy exists with joined inheritance and Firebird

1 Answers1