On Fri, Oct 11, 2019, at 3:56 PM, Victor Olex wrote:
> A bit of advocacy from my side on cx_Oracle:
> https://github.com/oracle/python-cx_Oracle/issues/365
>
> Mike, there's something you might want to look at. We have this monkey patch
> on SQLAlchemy in our recent code, which was necessary to get the correct
> behavior for NCHAR columns.
>
> from sqlalchemy.dialects.oracle import cx_oracle
> from sqlalchemy.sql sqltypes
>
> class _OracleNChar(sqltypes.NCHAR):
> def get_dbapi_type(self, dbapi):
> return dbapi.FIXED_NCHAR
>
> cx_oracle._OracleNChar = _OracleNChar
> cx_oracle.dialect.colspecs[sqltypes.NCHAR] = _OracleNChar
it seems likely that should be in the codebase as there is already:
class _OracleChar(sqltypes.CHAR):
def get_dbapi_type(self, dbapi):
return dbapi.FIXED_CHAR
can you open a bug report ?
>
>
> On Thursday, October 3, 2019 at 12:26:40 PM UTC-4, Mike Bayer wrote:
>> With cx_Oracle, you really should likely be using typing for everything as
>> cx_Oracle is pretty sensitive as well to the cursor.setinputsizes()
>> settings, which SQLAlchemy will do for you if you send in typed bound
>> parameters; additionally, you can set typing information for result columns
>> also (use text().columns()) which SQLAlchemy uses in order to set up
>> cursor.outputtypehandler. Both of these are cx_Oracle things that are
>> unfortunately unique to this DBAPI and they are hugely important; even the
>> django ORM has to use outputtypehandler.
>>
>> On Thu, Oct 3, 2019, at 12:20 PM, Mike Bayer wrote:
>>> hey there -
>>>
>>> you should apply typing behavior which should be safe to apply to any CHAR
>>> like this:
>>>
>>> class PaddedChar(TypeDecorator):
>>> impl = NCHAR
>>>
>>> def process_bind_param(self, value, dialect):
>>> if value is not None:
>>> value = value + (" " * (self.impl.length - len(value)))
>>> return value
>>>
>>> result = conn.execute(
>>> text("select * from nchartable where id = :id").bindparams(
>>> bindparam("id", type_=PaddedChar(4))
>>> ),
>>> {"id": "1"},
>>> ).fetchall()
>>>
>>>
>>>
>>>
>>> On Thu, Oct 3, 2019, at 4:47 AM, mdob wrote:
>>>> Hi everyone,
>>>>
>>>> There's IMO unusual behavior in Oracle when using bound parameters on
>>>> NCHAR column.
>>>>
>>>> from sqlalchemy import create_engine
>>>> from sqlalchemy.sql import text
>>>>
>>>>
>>>> e = create_engine('oracle://chinook:p4ssw0rd@localhost/xe')
>>>>
>>>>
>>>> result = e.execute(
>>>> text("select * from nchartable where id = '1'"),
>>>> ).fetchall()
>>>>
>>>>
>>>> print 'hardcoded:', list(result)
>>>>
>>>>
>>>> result = e.execute(
>>>> text('select * from nchartable where id = :id'),
>>>> {'id': '1'}
>>>> ).fetchall()
>>>>
>>>>
>>>> print 'trimmed:', list(result)
>>>>
>>>>
>>>>
>>>>
>>>> result = e.execute(
>>>> text('select * from nchartable where id = :id'),
>>>> {'id': '1 '} # padded with spaces
>>>> ).fetchall()
>>>>
>>>>
>>>> print 'padded:', list(result)
>>>>
>>>>
>>>> output
>>>> hardcoded: [(u'1 ',)]
>>>> trimmed: []
>>>> padded: [(u'1 ',)]
>>>>
>>>> When value is hardcoded or bound parameter is padded the statement works
>>>> as expected, but it doesn't when value is trimmed. Although the value in
>>>> where statement is just like in hardcoded case.
>>>>
>>>> As explained on cxOracle mailing list
>>>> https://sourceforge.net/p/cx-oracle/mailman/message/36775002/ it's a
>>>> deliberate decision to bind values str to VARCHAR2 and unicode to
>>>> NVARCHAR2. Unfortunately that doesn't work correctly for filtering on CHAR
>>>> and NCHAR.
>>>>
>>>> I know it's more cxOracle matter but how do you deal with this in
>>>> SQLAlchemy? Expecially when working with text SQL statement which may be
>>>> complex e.g. use stored procedures.
>>>>
>>>> Thanks for any clues,
>>>> Michal
>>>>
>>>> --
>>>> SQLAlchemy -
>>>> The Python SQL Toolkit and Object Relational Mapper
>>>>
>>>> http://www.sqlalchemy.org/
>>>>
>>>> To post example code, please provide an MCVE: Minimal, Complete, and
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>>>> description.
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>>>
>>>
>>> --
>>> SQLAlchemy -
>>> The Python SQL Toolkit and Object Relational Mapper
>>>
>>> http://www.sqlalchemy.org/
>>>
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>>> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
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>>
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
> To post example code, please provide an MCVE: Minimal, Complete, and
> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> description.
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--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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