On Dec 27, 2012, at 6:06 PM, Stefan Urbanek wrote:
>
> On 27.12.2012, at 23:21, Michael Bayer <[email protected]> wrote:
>
>>
>>
>> On Dec 27, 2012, at 4:55 PM, Stefan Urbanek wrote:
>>
>>> Hi,
>>>
>>> I am trying to pass multiple rows as tuples into an INSERT statement.:
>>>
>>> # buffer is list of lists/tuples, like: [ [1, "foo"], [2, "bar"], ... ]
>>> insert = self.table.insert()
>>> engine.execute(insert, buffer)
>>>
>>> This fails with:
>>>
>>> File
>>> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/SQLAlchemy-0.8.0b2-py2.7-macosx-10.8-x86_64.egg/sqlalchemy/engine/base.py",
>>> line 740, in _execute_clauseelement
>>> keys = distilled_params[0].keys()
>>> AttributeError: 'list' object has no attribute 'keys'
>>
>> It's the exception, rather than the rule, that the ordering of bound
>> parameters in a "compiled" statement can be controlled - a simple INSERT
>> statement yes, but for SELECT, UPDATE, DELETE the ultimate order of the
>> params in the compiled string might not correspond to the order in which the
>> bindparam() objects were created in the Python code. So you can pass a list
>> of lists in there but only if the statement you're executing is a raw
>> string, using the paramstyle of the target DBAPI. ClauseElement structures
>> only support named parameters as input params and you can see the error
>> where it's trying to detect "keys" is in _execute_clauseelement. the path
>> for a straight string is _execute_text.
>>
>
> Thanks for clear explanation.
>
> Is there a way how can I specify the order of params explicitly? I know the
> order always, as I am holding metadata for whole data processing pipeline.
Well its a matter of the syntax of the SQL statement, thats why positional
parameters are a little less than ideal to start with. There's ways to
reconcile these two systems but there's no natural API suggested by it. In
the case of an insert(), there is a natural order to the params which is the
order of columns in the table. You can do a quick dictionary translation like
this:
dict(zip((c.key for c in table.c), mytuple))
if the compiler were to accept positional parameters according to some ordering
system it would need to be doing a step like this internally in any case.
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