[Sqlalchemy-tickets] Issue #3487: Multi-dimensional ARRAY in Postgres aren't correctly supported by ORM's query builders (zzzeek/sqlalchemy)

[Andrey S. <iss...@bi...>]

New issue 3487: Multi-dimensional ARRAY in Postgres aren't correctly supported by ORM's query builders
https://bitbucket.org/zzzeek/sqlalchemy/issues/3487/multi-dimensional-array-in-postgres-arent

Andrey Semenov:

Here's just an example:

```
#!python

    weights = Column(ARRAY(DECIMAL(precision=2, asdecimal=False), dimensions=2), nullable=False, default=[])

```
then in query:

```
#!python

CallServiceCampaign.weights[
    func.idx(CallServiceCampaign.goods_ids, literal(goods_id))
][1] != None,

```
produces:

```
#!text

NotImplementedError: Operator 'getitem' is not supported on this expression
```

I think this is because https://bitbucket.org/zzzeek/sqlalchemy/src/447ee0af1d2fbb95f2f1244de301f2fe4a87a72f/lib/sqlalchemy/dialects/postgresql/base.py?at=rel_1_0_6#cl-911 doesn't handle `dimensions` parameter and always returns the underlying array's class on the first non-sliced reference.