[Sqlalchemy-tickets] Issue #3450: Accessing iterator on a query that has an error shows as not iterable (zzzeek/sqlalchemy)

[Michael B. <iss...@bi...>]

New issue 3450: Accessing iterator on a query that has an error shows as not iterable
https://bitbucket.org/zzzeek/sqlalchemy/issue/3450/accessing-iterator-on-a-query-that-has-an

Michael Brown:

Found on 1.0.3 and 1.0.4

I have a query that when evaluated throws a SQL error, except if the iterator is used. If the iterator is used then it shows as not iterable:

Normal:
```
In [66]: q = session.query(m.Panel).filter(m.Panel.ptype=='blood')

In [67]: map(lambda x: x, q)
Out[67]: 
[Panel(ptype='blood', id=74, name='bottle'),
 Panel(ptype='blood', id=75, name='space shuttle'),
 Panel(ptype='blood', id=76, name='russian'),
…
```

Failing:
```
In [68]: q = session.query(m.Panel).filter(m.Panel.ptype=='bloody')

In [69]: next(q)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
panel.py in <module>()
----> 1 next(q)

TypeError: Query object is not an iterator
```

What I think *should* happen is that the underlying error should be thrown like so when the iterator gets accessed (note the Query still shows as Iterable):

```
In [70]: q.first()
---------------------------------------------------------------------------
DataError                                 Traceback (most recent call last)
…
DataError: (psycopg2.DataError) invalid input value for enum panel_type: "bloody"
```