Re: [sqlalchemy] Oracle-Tg2 Combination,sqlalchemy error
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[sqlalchemy] Oracle-Tg2 Combination,sqlalchemy error
Hi,
I need help in setting up Oracle under TG/sqlalchemy environment.
I believe the issue is more of a SQLAlchemy issue and that is why i
am posting here.
Here's what i have done.
1.Installed TG2 and Sqlalchemy.
2.Installed Oracle Express 10g.
3.confirmed that I am able to access oracle using Sqlplus.
4.Installed cx_Oracle.
5.Wrote short test program in python to access my database using
cx_Oracle.The program worked fine.
Here's the test program.
import pkg_resources
pkg_resources.require(cx-Oracle=5.0.3)
import cx_Oracle
connstr='username/password@localhost'
conn = cx_Oracle.connect(connstr)
curs = conn.cursor()
curs.execute('select * from tabs')
print curs.description
print curs.fetchone()
conn.close()
6.started my application after configuring it for Oracle Express.
7.Here's the error I got.
File /root/tg2env/lib/python2.4/site-packages/
SQLAlchemy-0.5.6-py2.4.egg/sqlalchemy/engine/base.py, line 1229, in
contextual_connect
return self.Connection(self, self.pool.connect(),
close_with_result=close_with_result, **kwargs)
File /root/tg2env/lib/python2.4/site-packages/SQLAlchemy-0.5.6-
py2.4.egg/sqlalchemy/pool.py, line 142, in connect
return _ConnectionFairy(self).checkout()
File /root/tg2env/lib/python2.4/site-packages/SQLAlchemy-0.5.6-
py2.4.egg/sqlalchemy/pool.py, line 304, in __init__
rec = self._connection_record = pool.get()
File /root/tg2env/lib/python2.4/site-packages/SQLAlchemy-0.5.6-
py2.4.egg/sqlalchemy/pool.py, line 161, in get
return self.do_get()
File /root/tg2env/lib/python2.4/site-packages/SQLAlchemy-0.5.6-
py2.4.egg/sqlalchemy/pool.py, line 639, in do_get
con = self.create_connection()
File /root/tg2env/lib/python2.4/site-packages/SQLAlchemy-0.5.6-
py2.4.egg/sqlalchemy/pool.py, line 122, in create_connection
return _ConnectionRecord(self)
File /root/tg2env/lib/python2.4/site-packages/SQLAlchemy-0.5.6-
py2.4.egg/sqlalchemy/pool.py, line 198, in __init__
self.connection = self.__connect()
File /root/tg2env/lib/python2.4/site-packages/SQLAlchemy-0.5.6-
py2.4.egg/sqlalchemy/pool.py, line 261, in __connect
connection = self.__pool._creator()
File /root/tg2env/lib/python2.4/site-packages/SQLAlchemy-0.5.6-
py2.4.egg/sqlalchemy/engine/strategies.py, line 80, in connect
raise exc.DBAPIError.instance(None, None, e)
sqlalchemy.exc.DatabaseError: (DatabaseError) ORA-12505: TNS:listener
does not currently know of SID given in connect descriptor
None None
8. Here are the .ORA files.
TNSNAMES.ora
# tnsnames.ora Network Configuration File:
XE =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST =
localhost.localdomain)(PORT = 1521))
CONNECT_DATA = (SID = XE))
)
sqlnet.authentication_services = (NONE)
LISTENER.ORA
# listener.ora Network Configuration File:
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = /usr/lib/oracle/xe/app/
oracle/product/10.2.0/server)
(PROGRAM = extproc)
)
(SID_DESC =
(SID_NAME = m...@localhost)
(ORACLE_HOME = /usr/lib/oracle/xe/app/oracle/
product/10.2.0/server)
)
)
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC_FOR_XE))
(ADDRESS = (PROTOCOL = TCP)(HOST =
localhost.localdomain)(PORT = 1521))
)
)
DEFAULT_SERVICE_LISTENER = (XE)
SQLNET.ORA
This is the uncommented line in the sqlnet.ora
9.On googling ,I saw someone indicate that sql.authentication should
be set to none.
I did that but no avail.
I would really appreciate any help in resolving this problem.
Thanks.
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Re: [sqlalchemy] Oracle-Tg2 Combination,sqlalchemy error
On Apr 30, 2010, at 3:31 AM, dhanil anupurath wrote:
import pkg_resources
pkg_resources.require(cx-Oracle=5.0.3)
import cx_Oracle
connstr='username/password@localhost'
conn = cx_Oracle.connect(connstr)
I just want to go over how this is documented. From the cx_oracle
documentation at
http://cx-oracle.sourceforge.net/html/module.html#cx_Oracle.connect , we see
that the above is taken as the format user/p...@dsn, where dsn is the TNS
name from your tnsnames.ora file - ideally it would be the string xe, but it
seems to correlate the hostname of localhost as well.
Onto SQLAlchemy's, the document at
http://www.sqlalchemy.org/docs/reference/dialects/oracle.html?highlight=cx_oracle#connecting
states :
Connecting with create_engine() uses the standard URL approach of
oracle://user:p...@host:port/dbname[?key=valuekey=value...]. If dbname is
present, the host, port, and dbname tokens are converted to a TNS name using
the cx_oracle makedsn() function. Otherwise, the host token is taken directly
as a TNS name.
So the equivalent connect string is:
create_engine('oracle://user:password@localhost')
meaning, '/dbname' is not present, so the 'host' portion, in this case
'localhost', is sent to cx_Oracle.connect as the TNS name.
The usual way to connect looks like:
create_engine('oracle://user:password@localhost/xe')
the advantage to this approach is that SQLAlchemy uses cx_Oracle.makedsn() so
that no TNS entry is required.
Here are all the ways to connect to a localhost XE server:
import cx_Oracle
print cx_Oracle.connect('scott/ti...@localhost')
print cx_Oracle.connect('scott/ti...@xe')
print cx_Oracle.connect('scott', 'tiger', 'localhost')
print cx_Oracle.connect('scott', 'tiger', 'xe')
print cx_Oracle.connect('scott', 'tiger', cx_Oracle.makedsn('localhost', 1521,
'xe'))
from sqlalchemy import create_engine
print
create_engine('oracle://scott:ti...@localhost').connect().connection.connection
print create_engine('oracle://scott:ti...@xe').connect().connection.connection
print
create_engine('oracle://scott:ti...@localhost/xe').connect().connection.connection
output of this looks like:
cx_Oracle.Connection to sc...@localhost
cx_Oracle.Connection to sc...@xe
cx_Oracle.Connection to sc...@localhost
cx_Oracle.Connection to sc...@xe
cx_Oracle.Connection to
scott@(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521)))(CONNECT_DATA=(SID=xe)))
cx_Oracle.Connection to sc...@localhost
cx_Oracle.Connection to sc...@xe
cx_Oracle.Connection to
scott@(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521)))(CONNECT_DATA=(SID=xe)))
note the two forms of connection that use makedsn() have a locally-generated
TNS entry present.
Also note that SQLAlchemy is not using pkg_resources to import cx_Oracle. It
just calls import cx_Oracle. If the above pkg_resources call is required
(extremely unlikely), you need to call it before create_engine().
hope this helps.
# tnsnames.ora Network Configuration File:
XE =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST =
localhost.localdomain)(PORT = 1521))
CONNECT_DATA = (SID = XE))
)
sqlnet.authentication_services = (NONE)
LISTENER.ORA
# listener.ora Network Configuration File:
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = /usr/lib/oracle/xe/app/
oracle/product/10.2.0/server)
(PROGRAM = extproc)
)
(SID_DESC =
(SID_NAME = m...@localhost)
(ORACLE_HOME = /usr/lib/oracle/xe/app/oracle/
product/10.2.0/server)
)
)
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC_FOR_XE))
(ADDRESS = (PROTOCOL = TCP)(HOST =
localhost.localdomain)(PORT = 1521))
)
)
DEFAULT_SERVICE_LISTENER = (XE)
SQLNET.ORA
This is the uncommented line in the sqlnet.ora
9.On googling ,I saw someone indicate that sql.authentication should
be set to none.
I did that but no avail.
I would really appreciate any help in resolving this problem.
Thanks.
--
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sqlalchemy group.
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