[Sqlalchemy-tickets] Issue #3806: Postgres code generation is wrong for -> operator (HSTORE column access) pre-psql-9.5 (zzzeek/sqlalchemy)

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

New issue 3806: Postgres code generation is wrong for -> operator (HSTORE column access) pre-psql-9.5
https://bitbucket.org/zzzeek/sqlalchemy/issues/3806/postgres-code-generation-is-wrong-for

lincolnq:

On sqlalchemy 1.0.15, the below test code outputs "(test -> %(test_1)s) IS NOT NULL".

On sqlalchemy 1.1.0b3, it outputs "test -> %(test_1)s IS NOT NULL" -- note the omitted parentheses. 

The latter code is correct in Postgres 9.5 and above where the IS NOT NULL operator has lower precedence than ->, but below 9.5, the IS NOT NULL operator's precedence is higher than the -> operator but sqlalchemy still thinks it is lower.

```
#!python

from sqlalchemy import Column
from sqlalchemy.dialects import postgresql

col = Column(postgresql.HSTORE, name='test', primary_key=True)
print(str((col['key'] != None).compile(dialect=postgresql.dialect())))
```