On 8/4/15 1:41 PM, Abhishek Sharma wrote:
is this followings two instructions compulsory while defining new type?
m.drop_all(e)
m.create_all(e)
no that is just part of the demonstration script.
this instructions are not feasible , because DB team already defined
schema and normal user can not drop and create table.
yup, that is a given
On Tue, Aug 4, 2015 at 8:59 PM, Mike Bayer <[email protected]
<mailto:[email protected]>> wrote:
On 8/4/15 7:41 AM, Abhishek Sharma wrote:
in case lot of overhead will be there so it is better to use that
column label only
well it doesn't work anyway because data from a CLOB is not in
cx_oracle's world a "String", it's a LOB. The CLOB / NCLOB types
for cx_oracle are organized in their own way where only NCLOB
actually has unicode handling capability, regardless of the
coerce_to_unicode or convert_unicode flags; CLOB does not. So
either use NCLOB, or build out your own convert unicode, here is a
demo:
from sqlalchemy import create_engine, CLOB, Table, MetaData,
Column, select, TypeDecorator
from sqlalchemy.dialects.oracle import NCLOB
e = create_engine("oracle+cx_oracle://scott:tiger@xe", echo='debug')
class ForceUnicodeClob(TypeDecorator):
impl = CLOB
def process_result_value(self, value, dialect):
if value is not None:
value = value.decode('utf-8')
return value
m = MetaData()
t = Table('test', m, Column('data1', NCLOB()), Column('data2',
ForceUnicodeClob()))
m.drop_all(e)
m.create_all(e)
e.execute(t.insert(), data1=u'unicode', data2=u'unicode')
result = e.execute(select([t.c.data1, t.c.data2]))
value1, value2 = result.fetchone()
print repr(value1), repr(value2)
On Tue, Aug 4, 2015 at 6:15 AM, Mike Bayer
<[email protected] <mailto:[email protected]>> wrote:
On 8/4/15 5:47 AM, Abhishek Sharma wrote:
applying convert_unicode to CLOB type does not have any
effect. Still I am getting str type object from sqlalchemy
for CLOB type column
have you tried the coerce_to_unicode flag on create_engine() ?
On Mon, Aug 3, 2015 at 1:27 PM, Mike Bayer
<[email protected] <mailto:[email protected]>>
wrote:
On 8/3/15 1:04 PM, Abhishek Sharma wrote:
what about CLOB type? Unicode only handles String
type. Do i need to use convert_unicode there?
if your CLOB expects non-ascii characters then yes.
though on Oracle I thought you really need to be using
NCLOB for a col that stores unicode.
On Mon, Aug 3, 2015 at 6:56 PM, Mike Bayer
<[email protected]
<mailto:[email protected]>> wrote:
On 8/1/15 12:12 PM, Abhishek Sharma wrote:
Thanks for help. But still i have confusion over
encoding and decoding procedure which will take
place before retrieving and storing the results in DB.
In case if i am not using convert_unicode option
and data type is String so python process will
give str object to sqlalchemy at the time of
insert record in DB using ORM. So will alchemy
store that object in encoded form?. So at the time
of retrieving ORM will give str object for String
type column to python and python decode that
object with default encoding?
Can i simply use Unicode Data type for columns
where there might be chance of using non ascii data?
if you know that your unicode data is on specific
columns then yes, the Unicode type plugs in an
encoder/decoder for those backends that require it.
On Thu, Jul 30, 2015 at 2:55 AM, Mike Bayer
<[email protected]
<mailto:[email protected]>> wrote:
On 7/29/15 2:23 PM, Abhishek Sharma wrote:
We are using sqlalchemy version 0.7, python
2.7 and oracle Database.
We have ASCII as default python encoding and
DB have ISO-8052 encoding. Our DB tables
contains some of characters which are out of
ASCII range. So when we are running query on
those tables we are getting Unicode Decode
error saying "ASCII" codec can not decode.
This error we are getting without accessing
model attributes.
How i can handle these errors without
changing python default encoding.
Oracle's client encoding is controlled by the
NLS_LANG environment variable. That has to be
set correctly first off (see
http://www.oracle.com/technetwork/products/globalization/nls-lang-099431.html).
If you have non-ASCII strings encoded in
datatypes that are explicitly not of type
NVARCHAR or NCLOB , or you're relying on a lot
of raw SQL, and you are still getting errors,
I would set the "coerce_to_unicode=True" flag
on create_engine(), which allows cx_Oracle's
unicode facilities to take place fully for all
string data being returned, at the expense of
some performance. See
http://docs.sqlalchemy.org/en/rel_1_0/dialects/oracle.html#unicode
for background.
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