polars.read_database can not work with duckdb_engine connection.

[specter119]

Checks

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of Polars.

Reproducible example

import duckdb
import polars as pl
import sqlalchemy
from sqlalchemy import create_engine, text

duckdb.__version__, pl.__version__, sqlalchemy.__version__, duckdb_engine.__version__
# ('1.0.0', '1.5.0', '2.0.32', '0.13.1')

duckdb.sql('select 42;')
#┌───────┐
#│  42   │
#│ int32 │
#├───────┤
#│    42 │
#└───────┘

engine = create_engine('duckdb:///:memory:')
engine.connect().execute(text('SELECT 42')).fetchall()
#[(42,)]

pl.read_database('SELECT 42;', connection=engine.connect())

Log output

{
	"name": "AttributeError",
	"message": "'duckdb.duckdb.DuckDBPyConnection' object has no attribute 'c'",
	"stack": "---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
Cell In[2], line 6
      3 engine = create_engine('duckdb:///:memory:')
      4 display(engine.connect().execute(text('SELECT 42')).fetchall())
----> 6 pl.read_database('SELECT 42;', connection=engine.connect())

File /opt/python3.12/lib/python3.12/site-packages/polars/io/database/functions.py:253, in read_database(query, connection, iter_batches, batch_size, schema_overrides, infer_schema_length, execute_options)
    250         raise ValueError(msg)
    252 # return frame from arbitrary connections using the executor abstraction
--> 253 with ConnectionExecutor(connection) as cx:
    254     return cx.execute(
    255         query=query,
    256         options=execute_options,
   (...)
    261         infer_schema_length=infer_schema_length,
    262     )

File /opt/python3.12/lib/python3.12/site-packages/polars/io/database/_executor.py:94, in ConnectionExecutor.__init__(self, connection)
     91 if self.driver_name == \"surrealdb\":
     92     connection = SurrealDBCursorProxy(client=connection)
---> 94 self.cursor = self._normalise_cursor(connection)
     95 self.result: Any = None

File /opt/python3.12/lib/python3.12/site-packages/polars/io/database/_executor.py:387, in ConnectionExecutor._normalise_cursor(self, conn)
    385 elif conn.engine.driver == \"duckdb_engine\":
    386     self.driver_name = \"duckdb\"
--> 387     return conn.engine.raw_connection().driver_connection.c
    388 elif self._is_alchemy_engine(conn):
    389     # note: if we create it, we can close it
    390     self.can_close_cursor = True

File /opt/python3.12/lib/python3.12/site-packages/duckdb_engine/__init__.py:95, in ConnectionWrapper.__getattr__(self, name)
     94 def __getattr__(self, name: str) -> Any:
---> 95     return getattr(self.__c, name)

AttributeError: 'duckdb.duckdb.DuckDBPyConnection' object has no attribute 'c'"
}

Issue description

read_database can not working properly

Expected behavior

return the unit cell table of 42

change https://github.com/pola-rs/polars/blob/main/py-polars/polars/io/database/_executor.py#L387
as: return conn.engine.raw_connection().driver_connection._ConnectionWrapper__c can fixed, but not sure the impact (from which version duckdb-engine change the behivor)

Installed versions

--------Version info---------
Polars:               1.5.0
Index type:           UInt32
Platform:             Linux-5.15.146.1-microsoft-standard-WSL2-x86_64-with-glibc2.34
Python:               3.12.5 | packaged by conda-forge | (main, Aug  8 2024, 18:36:51) [GCC 12.4.0]

----Optional dependencies----
adbc_driver_manager:  <not installed>
cloudpickle:          <not installed>
connectorx:           <not installed>
deltalake:            <not installed>
fastexcel:            <not installed>
fsspec:               2024.6.1
gevent:               <not installed>
great_tables:         <not installed>
hvplot:               <not installed>
matplotlib:           3.9.2
nest_asyncio:         1.6.0
numpy:                1.26.4
openpyxl:             3.1.5
pandas:               2.2.2
pyarrow:              17.0.0
pydantic:             2.8.2
pyiceberg:            <not installed>
sqlalchemy:           2.0.32
torch:                2.3.1.post300
xlsx2csv:             <not installed>
xlsxwriter:           <not installed>

[alexander-beedie]

Thanks for the heads-up; looks like a very simple fix on our side ;)