TypeError: cannot unpack non-iterable function object

[aiscience01]

Hello,

While using Cloud Sql Connector from Google (https://github.com/GoogleCloudPlatform/cloud-sql-python-connector) that is using pg8000 connector for database connections in Flask-SQLAlchamy plugin, faced an issue that we first reported to Google Cloud Platforms (GoogleCloudPlatform/cloud-sql-python-connector#548). After some investigation by them, they concluded it could be a pg8000 issue and advised to create an issue here. Below is more detail to reproduce the error:

The error can be reproduced when trying to connect to GCP Postgresql instances using Flask-SQLAlchemy extension. The code works when trying to use standard python pgsql connectors to GCP Posgtgres instance using TCP connections. When using this library-the Flask-SQLAlchemy extension- pg8000 raises an error on setting the correct field size for a string field (creating a team name), and raises the following error:

manager.dispatch.init_failure(self, args, kwargs)
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/util/langhelpers.py", line 70, in exit
compat.raise_(
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/util/compat.py", line 207, in raise_
raise exception
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/orm/state.py", line 477, in _initialize_instance
return manager.original_init(*mixed[1:], **kwargs)
File "/home/app/flask/project/models/user.py", line 65, in init
ModelProxy.teams.Team.create(team_name, self)
File "/home/app/flask/project/models/init.py", line 158, in wrapper
value = f(*args, **kwds)
File "/home/app/flask/project/models/teams/team.py", line 68, in create
db.session.commit()
File "", line 2, in commit
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 1428, in commit
self._transaction.commit(_to_root=self.future)
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 829, in commit
self._prepare_impl()
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 808, in _prepare_impl
self.session.flush()
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 3345, in flush
self._flush(objects)
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 3485, in flush
transaction.rollback(capture_exception=True)
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/util/langhelpers.py", line 70, in exit
compat.raise(
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/util/compat.py", line 207, in raise
raise exception
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 3445, in _flush
flush_context.execute()
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/orm/unitofwork.py", line 456, in execute
rec.execute(self)
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/orm/unitofwork.py", line 630, in execute
util.preloaded.orm_persistence.save_obj(
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/orm/persistence.py", line 244, in save_obj
_emit_insert_statements(
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/orm/persistence.py", line 1221, in _emit_insert_statements
result = connection._execute_20(
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1614, in _execute_20
return meth(self, args_10style, kwargs_10style, execution_options)
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/sql/elements.py", line 325, in _execute_on_connection
return connection._execute_clauseelement(
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1481, in _execute_clauseelement
ret = self._execute_context(
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1731, in _execute_context
context._set_input_sizes()
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/engine/default.py", line 1678, in _set_input_sizes
self.root_connection.handle_dbapi_exception(
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 2030, in handle_dbapi_exception
util.raise(exc_info[1], with_traceback=exc_info[2])
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/util/compat.py", line 207, in raise
raise exception
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/engine/default.py", line 1674, in _set_input_sizes
self.dialect.do_set_input_sizes(
File "/usr/local/lib/python3.9/site-packages/sqlalchemy/dialects/postgresql/pg8000.py", line 519, in do_set_input_sizes
cursor.setinputsizes(
File "/usr/local/lib/python3.9/site-packages/pg8000/dbapi.py", line 621, in setinputsizes
oid, _ = self._c.py_types[size]
TypeError: cannot unpack non-iterable function object

Flask open source project that is used as a baseline: https://github.com/Sumukh/Ignite
OS type and version: Debian 11
Python version: Python 3.9.15
Connector version: pg8000 installed with: pip install "cloud-sql-python-connector[pg8000]"
Flask-SQLAlchemy extension

Related Google Connector Github issue: GoogleCloudPlatform/cloud-sql-python-connector#548

[aiscience01]

As this is still under investigation in Google Cloud Connector side, and I read that it may be an issue there, I am closing this and may re-open if that investigation has more insight on potential source.

[tlocke]

Hi @aiscience01, this is indeed a bug in pg8000, thanks for reporting it. It should now be fixed in version 1.29.4. I'll also add a message under the original bug.