On Aug 28, 2013, at 10:11 PM, gbr <doubl...@directbox.com> wrote:
> Hi,
>
> Before spamming the issue tracker and since I'm new to SQLAlchemy and may
> have misunderstood how to use `append_whereclause()`, I thought I seek
> confirmation on this mailing list.
>
> The code:
>
> def test_append_whereclause(self):
> url = 'localhost'
> username = 'donald'
> password = 'duck'
> database_name = 'test_db'
> engine = create_engine('postgres://%s:%s@%s/%s' % (username,
> password, url, database_name))
> session = sessionmaker(bind=engine)()
>
> location = Table('location', metadata,
> Column('id', Integer, Sequence('seq_location_id')),
> Column('name', String(256), nullable=False),
> Column('domestic', Boolean, default=False),
> )
>
> query = select(
> columns=[location.c.id.label('id')],
> from_obj=location,
> whereclause=location.c.id>50
> )
> query.append_whereclause(query.c.id < 100)well you're creating a cycle here by embedding a column with a parent of select object "q", in the WHERE clause of select object "q". to compile the WHERE clause of "query" means we look at "query.c.id" which means we must render the table "query" which is how it cycles. Whether or not this kind of thing can be faithfully detected (a simple self-referential cycle is one thing, but a more deeply nested cycle would be more expensive to detect), from a usage standpoint the operation does not make sense. suppose "query" is this: SELECT id FROM table query.c.id is basically this column: SELECT ---> id <--- FROM (SELECT id FROM table) that is, it's on the outside of "query" - it's one of the columns it exports. it doesn't make any sense to refer to it in the WHERE clause of the embedded query. What it seems like you're looking to do is where(location.c.id < 100).
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