dbapi Cursor.description should be none for statement that don't return rows

[CaselIT]

What happened?

The python dbapi spect specifies that descriptor should be none if a statement does not return any data: https://peps.python.org/pep-0249/#description

This attribute will be None for operations that do not return rows or if the cursor has not had an operation invoked via the .execute*() method yet.

Stack Trace

Traceback (most recent call last):
  File "foo.py", line 259, in <module>
    assert cur.description is None, cur.description
           ^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: []

How can we reproduce the bug?

from adbc_driver_postgresql.dbapi import connect
url = 'postgresql://scott:tiger@localhost/test' 
with connect(url) as conn, conn.cursor() as cur:
    cur.execute('create table t(a int)')
    assert cur.description is None, cur.description

Environment/Setup

adbc_driver_manager = 1.8.0
adbc_driver_postgresql = 1.8.0

[lidavidm]

Sorry for the radio silence here - I think we should first clarify in the spec what to do when this happens (probably the driver can indicate the result set is empty by returning an Arrow schema with no columns - I think this is valid and also something you can never normally achieve with SQL?). Then the Python bindings can look for this and reflect it properly

[CaselIT]

I worked around that by using a custom cursor class that returns none if description is empty. It's not a "correct" solution but works for my use case.

I think this is valid and also something you can never normally achieve with SQL?

I think it may be possible in postgresql, since you can define a table with no columns, then select from it, leading to a result set with no columns. The following it accepted by pg

create table a();
select * from a;

but I wouldn't call this "normally achiavable" in sql