OpenEdge support not working in master. Some basic fixes here

[AkshayGuleria]

Some details before we start:

• Django App name: sports_demo_odbc
• CLASSPATH is set correctly. Tested using python shell and pyodbc connection.
• Settings

DATABASES = {
    'default': {
        'ENGINE': "django_pyodbc",
        'HOST': "localhost,11001",
        'USER': "akguleri",
        'PASSWORD': "notAdmin",
        'NAME': "sports_demo",
        'OPTIONS': {
           'host_is_server': True,
           'dsn': 'dsn_sports_demo',
           'openedge': True
        },
    }   
} 

• Django version = 1.10.6

I hope you have tried checking if the OpenEdge is supported as the documentation says. I tried this but didn't work. The connection establishment works fine (using python manage.py runserver) but the queries made to OpenEdge database are not correct. I fixed most of them by hand and reached to the point where at least the server was started without any errors.
Below are the errors that I got (in the same order) and fixed them by hand to make it work.

1. Error on fetching TABLES from OpenEdge DB:
   Query:

File "/usr/local/lib/python2.7/dist-packages/django_pyodbc-1.1.0-py2.7.egg/django_pyodbc/introspection.py", line 95, in get_table_list
    cursor.execute("SELECT TABLE_NAME, 't' FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_TYPE = 'BASE TABLE'")

Error:

File "/usr/local/lib/python2.7/dist-packages/django_pyodbc-1.1.0-py2.7.egg/django_pyodbc/base.py", line 495, in execute
    raise utils.DatabaseError(*e.args)
django.db.utils.DatabaseError: ('HY000', '[HY000] [DataDirect][ODBC Progress OpenEdge Wire Protocol driver][OPENEDGE]Table/view/synonynm "INFORMATION_SCHEMA.TABLES" cannot be found. (15814) (-210083) (SQLExecDirectW)')

Correct Query should be:

if <is_opendge>:
       cursor.execute("SELECT TBL, 't' FROM SYSPROGRESS.SYSTABLES WHERE TBLTYPE = 'T'")

• Fix submitted via Openedge support fixes #140

2. SchemaEditorClass attribute:
   Error:

File "/usr/local/lib/python2.7/dist-packages/django/db/backends/base/base.py", line 604, in schema_editor
    'The SchemaEditorClass attribute of this database wrapper is still None')
NotImplementedError: The SchemaEditorClass attribute of this database wrapper is still None

I commented the call to schema_editor (in recorder.py) since it tries to create tables using create_model. There should be some way to control this. I don't want to create/change my OpenEdge schema over this API. Perhaps I'm too new to this area that I don't know how to control this behaviour. It would be nice if you can guide me on this.

This can be controlled by disabling self.check_migrations for OpenEdge connections but that has to be done in django's runserver.py file. So this error does not concern this adapter.

3. AttributeError:
   Error:

File "/usr/local/lib/python2.7/dist-packages/django_pyodbc-1.1.0-py2.7.egg/django_pyodbc/compiler.py", line 204, in as_sql
    self._fix_aggregates()
  File "/usr/local/lib/python2.7/dist-packages/django_pyodbc-1.1.0-py2.7.egg/django_pyodbc/compiler.py", line 180, in _fix_aggregates
    for alias, aggregate in self.query.aggregate_select.items():
AttributeError: 'Query' object has no attribute 'aggregate_select'

The _fix_aggregates function perhaps is meant to counter some MSSQL behaviour as the comment says in the code. I'm not 100% sure though. Again I used self.connection.ops.is_openedge and prevent the execution of that function.

4. Migration problem again:
   Error:

File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 64, in execute  return self.cursor.execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django_pyodbc-1.1.0-py2.7.egg/django_pyodbc/base.py", line 496, in execute  raise utils.DatabaseError(*e.args)
django.db.utils.DatabaseError: ('HY000', '[HY000] [DataDirect][ODBC Progress OpenEdge Wire Protocol driver][OPENEDGE]Table/view/synonynm "AKGULERI.django_migrations" cannot be found. (15814) (-210083) (SQLExecDirectW)')

This might be Django framework itself but it tries get something Djnago specific which is not available in OpenEdge DB. Here too I made a dirty fix and avoided execution of such query by replacing it with simple query i.e. SELECT TOP 1 * FROM SYSPROGRESS.SYSTABLES. Any guidance on this would be helpful as well.

This can be controlled by disabling self.check_migrations for OpenEdge connections but that has to be done in django's runserver.py file. So this error does not concern this adapter.

5. Query quotes: After all this the server started I created a simple model for Customer table (having Meta class db_table = 'PUB.CUSTOMER') of the connected OpenEdge DB. Then using shell I created a instance of Customer and tried to fetch some data using customer.objects.get(pk=1) but was returned the below with an error on the shell. The query it formed was something like this
   SELECT "PUB.CUSTOMER"."custnum", "PUB.CUSTOMER"."name", "PUB.CUSTOMER"."city" FROM "PUB.CUSTOMER" WHERE "PUB.CUSTOMER"."custnum" = ?
   This query did not yield any result until the quotes were. So I change the function quote_name in operations.py to return unquoted name variable if self.is_openedge. Progress does support querying with quotes but this was perhaps an odd occasion where this query was not formed correctly.

• Fix submitted via Openedge support fixes #140

Now (finally :)) the query customer.objects.get(pk=1) gets me results from the DB. But perhaps these fixes should be done properly into the django-pyodbc code.