no, I didn't dive into sqlalchemy to read the source code
2016-04-16 6:41 GMT+08:00 Bo Yang <tebor...@google.com>:
> Do you know what kind of interface the custom class needs to provide in
> order to use sqlalchemy?
>
> On Tue, Apr 12, 2016 at 8:57 PM GoldenBull Chen <goldenb...@gmail.com>
> wrote:
>
>> I have an existing table in Oracle:
>> --------------------------------------------------------
>> CREATE TABLE test_tbl
>> (
>> id NUMBER,
>> name VARCHAR2 (100),
>> val NUMBER,
>> CONSTRAINT test_tbl_pk PRIMARY KEY (id)
>> );
>> ---------------------------------------------------------
>>
>>
>> In python, I tried to load the table using sqlalchemy, and everything works
>> fine:
>>
>> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>>
>> # -*- encoding: utf8 -*-
>>
>> from pbtest_pb2 import *
>> from sqlalchemy import *
>> from sqlalchemy.orm import *
>>
>> metadata = MetaData()
>>
>> tbl = Table('TEST_TBL', metadata,
>> Column('id', Integer, primary_key=True),
>> Column('name', String(100)),
>> Column('val', Numeric),
>> )
>>
>>
>> class TestType2(object):
>> pass
>>
>>
>> t = TestType2 # note here, mapped to a custom class
>>
>> mapper(t, tbl)
>> engine = create_engine('oracle+cx_oracle://user:passwd@machine/orcl')
>> Session = sessionmaker(bind=engine)
>> session = Session()
>> for i in session.query(t):
>> print(i.id, i.name, i.val)
>>
>> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>>
>>
>>
>> And here is the corresponding protobuf definition:
>> ---------------------------------------------------------
>> syntax = "proto3";
>>
>>
>> message TestType
>> {
>> int32 id = 1;
>> string name = 2;
>> double val = 3;
>> }
>>
>> ---------------------------------------------------------
>>
>>
>>
>> Now I want to re-use the class generated by proto compiler, so I change
>> the class used in mapping:
>> ---------------------------------------------------------
>>
>> t = TestType # now mapped to the generated class
>>
>> ---------------------------------------------------------
>>
>>
>> Then the piece of code failed with error:
>>
>> ---------------------------------------------------------
>>
>> Traceback (most recent call last):
>> File "D:/test/pbtest.py", line 22, in <module>
>> mapper(t, tbl)
>> File "<string>", line 2, in mapper
>> File "C:\Anaconda2\lib\site-packages\sqlalchemy\orm\mapper.py", line 629,
>> in __init__
>> self._configure_pks()
>> File "C:\Anaconda2\lib\site-packages\sqlalchemy\orm\mapper.py", line 1223,
>> in _configure_pks
>> (self, self.mapped_table.description))
>> sqlalchemy.exc.ArgumentError: Mapper Mapper|TestType|TEST_TBL could not
>> assemble any primary key columns for mapped table 'TEST_TBL'
>> ---------------------------------------------------------
>>
>>
>> Is it possible to reuse the generated class with sqlalchemy?
>>
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>
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