getconn() doesn't work with NamedTupleCursor about momoko

[haizaar]

Hi Chen,
Thanks for the report.

As a quick check, can you try this cursor class with plain psycopg2 in your
environment?
On Apr 26, 2014 8:13 PM, "Chen Tao" [email protected] wrote:

Greetings. As the title suggests, getconn() doesn't play well with
NamedTupleCursor.

Here's a test case:

import psycopg2
import momoko
from psycopg2.extras import NamedTupleCursor
from tornado.testing import AsyncTestCase, gen_test
import unittest
import os

class ConnNamedTuple(AsyncTestCase):
def setUp(self):
super().setUp()
self.db = momoko.Pool(
dsn='dbname=dbdb user=%s host=localhost port=5432' % os.environ['USER'],
size=3,
ioloop=self.io_loop,
callback=self.stop,
cursor_factory=NamedTupleCursor
)
self.wait()

def tearDown(self):
    self.db.close()
    self.io_loop.close()

@gen_test
def test_conn_namedtuple(self):
    yield momoko.Op(self.db.getconn)

unittest.main()

Here's the stack trace:

ERROR: test_conn_namedtuple (main.ConnNamedTuple)

Traceback (most recent call last):
File "/usr/local/lib/python3.4/dist-packages/tornado/testing.py", line 427, in wrapper
functools.partial(f, self), timeout=timeout)
File "/usr/local/lib/python3.4/dist-packages/tornado/ioloop.py", line 389, in run_sync
return future_cell[0].result()
File "/usr/local/lib/python3.4/dist-packages/tornado/concurrent.py", line 129, in result
raise_exc_info(self.**exc_info)
File "", line 3, in raise_exc_info
File "/usr/local/lib/python3.4/dist-packages/tornado/gen.py", line 206, in handle_exception
if runner is not None and runner.handle_exception(typ, value, tb):
File "/usr/local/lib/python3.4/dist-packages/tornado/gen.py", line 580, in handle_exception
self.run()
File "/usr/local/lib/python3.4/dist-packages/tornado/gen.py", line 529, in run
yielded = self.gen.throw(_exc_info)
File "tmp/conn_namedtuple.py", line 26, in test_conn_namedtuple
yield momoko.Op(self.db.getconn)
File "/usr/local/lib/python3.4/dist-packages/tornado/stack_context.py", line 302, in wrapped
ret = fn(_args, kwargs)
File "/usr/local/lib/python3.4/dist-packages/momoko/connection.py", line 594, in io_callback
self.callback(None)
File "/usr/local/lib/python3.4/dist-packages/momoko/connection.py", line 640, in _ping_callback
cursor.fetchall()
File "/usr/local/lib/python3.4/dist-packages/psycopg2/extras.py", line 317, in fetchall
nt = self.Record = self._make_nt()
File "/usr/local/lib/python3.4/dist-packages/psycopg2/extras.py", line 340, in _make_nt
return namedtuple("Record", [d[0] for d in self.description or ()])
File "/usr/lib/python3.4/collections/__init.py", line 338, in namedtuple
'identifiers: %r' % name)
ValueError: Type names and field names must be valid identifiers: '?column?'

---

Ran 1 test in 0.031s

FAILED (errors=1)

I'm on Python 3.4. pip freeze output, all are PyPI releases.

Momoko==1.1.2
psycopg2==2.5.2
tornado==3.2

I think it's easy to workaround but it's a little bit annoying. Thanks in
advance.

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/74
.

[jagt]

@haizaar

You're right it's the same problem with psycopg2. I'm closing this and will report there. Thanks!

[encorehu]

this is actually momoko's error

see psycopg/psycopg2#211

cur.execute("SELECT 'ok';")

need to be:

cur.execute("SELECT 'ok' as blah;")

if you used NamedTupleCursor.

AND, the error occured at connection.py line 635

cursor.execute("SELECT 1")

and i modified it to

cursor.execute("SELECT 1 as ping")

which temp fixed.

[haizaar]

You are right - this is a real bug.

[indarian]

Hello! It seems like the same error exists with register_hstore():

Traceback (most recent call last):
      File "/usr/local/lib/python3.4/dist-packages/tornado/ioloop.py", line 565, in _run_callback
        ret = callback()
      File "/usr/local/lib/python3.4/dist-packages/tornado/stack_context.py", line 275, in null_wrapper
        return fn(*args, **kwargs)
      File "/usr/local/lib/python3.4/dist-packages/momoko/connection.py", line 864, in _register
        oid, array_oid = cursor.fetchone()
      File "/usr/local/lib/python3.4/dist-packages/psycopg2/extras.py", line 303, in fetchone
        nt = self.Record = self._make_nt()
      File "/usr/local/lib/python3.4/dist-packages/psycopg2/extras.py", line 340, in _make_nt
        return namedtuple("Record", [d[0] for d in self.description or ()])
      File "/usr/lib/python3.4/collections/__init__.py", line 348, in namedtuple
        raise ValueError('Encountered duplicate field name: %r' % name)
    ValueError: Encountered duplicate field name: 'oid'

I guess it is needed to use aliases as in this issue on this line:
https://github.com/FSX/momoko/blob/master/momoko/connection.py#L890