[Sqlalchemy-tickets] Issue #4229: PostgreSQL DATERANGE(): comparison with None does not generate expected "IS NOT NULL" (zzzeek/sqlalchemy)

[Lele G. <iss...@bi...>]

New issue 4229: PostgreSQL DATERANGE(): comparison with None does not generate expected "IS NOT NULL"
https://bitbucket.org/zzzeek/sqlalchemy/issues/4229/postgresql-daterange-comparison-with-none

Lele Gaifax:

The following script:

```
#!python

import sqlalchemy as sa
import sqlalchemy.orm as orm
import sqlalchemy.types as types
import sqlalchemy.dialects.postgresql as sapg


md = sa.MetaData()


testtable = sa.Table(
    'testtable', md,
    sa.Column('id', types.Integer(),
              primary_key=True,
              nullable=False),
    sa.Column('name', types.Unicode(192),
              nullable=False),
    sa.Column('visibility', sapg.DATERANGE())
)


class Base:
    def __init__(self, **kwargs):
        for k in kwargs:
            setattr(self, k, kwargs[k])


class TestTable(Base):
    pass


orm.mapper(TestTable, testtable)


e = sa.create_engine('postgresql://localhost/test', echo=True)
md.create_all(e)


s = orm.Session(e)

o1 = TestTable(id=1, name='foo')
s.add(o1)
s.commit()

q = s.query(TestTable).filter(TestTable.name != None)
print(str(q))
q = s.query(TestTable).filter(TestTable.name == None)
print(str(q))

q = s.query(TestTable).filter(TestTable.visibility != None)
print(str(q))
q = s.query(TestTable).filter(TestTable.visibility == None)
print(str(q))
```

prints:
```
SELECT testtable.id AS testtable_id, testtable.name AS testtable_name, testtable.visibility AS testtable_visibility 
FROM testtable 
WHERE testtable.name IS NOT NULL
SELECT testtable.id AS testtable_id, testtable.name AS testtable_name, testtable.visibility AS testtable_visibility 
FROM testtable 
WHERE testtable.name IS NULL
SELECT testtable.id AS testtable_id, testtable.name AS testtable_name, testtable.visibility AS testtable_visibility 
FROM testtable 
WHERE testtable.visibility <> %(visibility_1)s
SELECT testtable.id AS testtable_id, testtable.name AS testtable_name, testtable.visibility AS testtable_visibility 
FROM testtable 
WHERE testtable.visibility IS NULL
```

Am I missing something or is this unexpected?