[Sqlalchemy-tickets] Issue #3642: Endless loop with `foo in arraycolumn` (zzzeek/sqlalchemy)

[thiefmaster <iss...@bi...>]

New issue 3642: Endless loop with `foo in arraycolumn`
https://bitbucket.org/zzzeek/sqlalchemy/issues/3642/endless-loop-with-foo-in-arraycolumn

thiefmaster:

This example never terminates:

```python
from sqlalchemy import *
from sqlalchemy.dialects.postgresql import ARRAY
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import *


Base = declarative_base()


class Foo(Base):
    __tablename__ = 'foo'

    id = Column(Integer, primary_key=True)
    chain = Column(ARRAY(Integer))


e = create_engine('postgresql:///test', echo=True)
Base.metadata.create_all(e)
s = Session(e)

print s.query(Foo).filter(123 in Foo.chain).all()
```



Traceback on ^C:

```pytb
^CTraceback (most recent call last):
  File "satest.py", line 22, in <module>
    print s.query(Foo).filter(123 in Foo.chain).all()
  File "/home/adrian/dev/indico/env/lib/python2.7/site-packages/sqlalchemy/sql/operators.py", line 301, in __eq__
    return self.operate(eq, other)
  File "/home/adrian/dev/indico/env/lib/python2.7/site-packages/sqlalchemy/sql/elements.py", line 739, in operate
    return op(self.comparator, *other, **kwargs)
  File "/home/adrian/dev/indico/env/lib/python2.7/site-packages/sqlalchemy/sql/operators.py", line 301, in __eq__
    return self.operate(eq, other)
  File "<string>", line 1, in <lambda>
  File "/home/adrian/dev/indico/env/lib/python2.7/site-packages/sqlalchemy/sql/type_api.py", line 60, in operate
    return o[0](self.expr, op, *(other + o[1:]), **kwargs)
  File "/home/adrian/dev/indico/env/lib/python2.7/site-packages/sqlalchemy/sql/default_comparator.py", line 69, in _boolean_compare
    negate=negate, modifiers=kwargs)
  File "/home/adrian/dev/indico/env/lib/python2.7/site-packages/sqlalchemy/sql/elements.py", line 2734, in __init__
    self.type = type_api.to_instance(type_)
KeyboardInterrupt
```

>From looking at the code `__contains__` is not supported, but it should result in an exception and not in a hang.

---

Also, I think it would be useful to implement `__contains__` to call `self.contains([value])`. Using `.any(123)` is not an option since it does not make use of a GIN index on the table, while `.contains([123])` does even though both do the same thing.