On Feb 7, 2011, at 11:16 AM, Kent wrote:
> On Feb 4, 12:04 pm, Kent <jkentbo...@gmail.com> wrote:
>> Excellent, it is working for the simpler case, but for oracle 8 (who
>> isn't as smart when indexing) I also need it to work for
>> subqueryload().
>>
>> So the problem is that my FOR UPDATE OF is also being added for
>> subqueryload selects.
>>
>> * Can I tell within the compiles context if this is for subqueryload?
>> (Or can the Query tell?)
>
>
> What I worked out based on compiler.is_subquery() is that
> compiler.stack (in other words, bool(compiler.stack)) should tell me
> if this is a subqueryload. Does that sound accurate?
yes that is actually the appropriate way to detect if the current context is
that of a subquery. (is_subquery() that is. I'd prefer that over peeking
into the stack itself).
>
>
>>
>> * Are there other cases where the query is "reused" that I need to be
>> careful of?
>>
>> I restructured this way (as you're original suggestion to fix another
>> issue):
>>
>> @compiles(Select)
>> def compile_forupdateof(select, compiler, **kw):
>> rendered = compiler.visit_select(select, **kw)
>> if hasattr(select, '_for_update_of'):
>> mapper = class_mapper(select._for_update_of)
>> name = mapper.mapped_table.name
>> if compiler.dialect.name == 'oracle':
>> # Oracle makes us specify the column name (for views, I
>> guess, since it locks entire row)
>> name += '.' + mapper.primary_key[0].name
>> rendered = "%s FOR UPDATE OF %s" % (rendered, name)
>> return rendered
>>
>> On Feb 3, 9:51 pm, Michael Bayer <mike...@zzzcomputing.com> wrote:
>>
>>> On Feb 3, 2011, at 9:29 PM, Kent wrote:
>>
>>>> Yeah, I wanted to apologize because my heart wants to contribute to
>>>> the project (really), but I'm working overtime like mad swamped
>>>> because our product is live in use now and I've got a backload of
>>>> tickets to solve! I also feel my level of understanding currently is
>>>> more hacking than contributing. I hope to be of more help to the
>>>> project in the future.
>>
>>>> Is "simpler than you had in mind" a good thing or am I over
>>>> simplifying and it won't work for bunch of cases?
>>
>>>> I note that the simple case is working, but something like this fails:
>>
>>>> DBSession.query(Order).for_update_of(Order).limit(10).all()
>>
>>>> since I really need to have the for update inside in this case... any
>>>> advise or is this what you meant by "There's not a great way to
>>>> intercept the middle of the SELECT compilation with a new kind of
>>>> clause in this case."?
>>
>>> i think if it works for what you need right now, then its great.
>>> @compiles is meant to give you what you need to get out of a jam.
>>
>>>> On Feb 3, 9:07 pm, Michael Bayer <mike...@zzzcomputing.com> wrote:
>>>>> oh OK this is a little simpler than what I had in mind, you just have to
>>>>> add the mixin expression.Executable to your ForUpdateOf class.
>>
>>>>> On Feb 3, 2011, at 9:05 PM, Kent wrote:
>>
>>>>>> Here is a crude outline (need to properly escape table name, etc.), of
>>>>>> what I think might work, and it seems to render properly, but crashes
>>>>>> with:
>>
>>>>>> File "/home/rarch/tg2env/lib/python2.6/site-packages/
>>>>>> SQLAlchemy-0.6.4.2kbdev-py2.6-linux-x86_64.egg/sqlalchemy/engine/
>>>>>> default.py", line 353, in __init__
>>>>>> raise exc.ArgumentError("Not an executable clause: %s" % compiled)
>>>>>> ArgumentError: Not an executable clause:
>>>>>> ...
>>
>>>>>> class MyQuery(Query):
>>>>>> _for_update_of = None
>>
>>>>>> @_generative()
>>>>>> def for_update_of(self, arg):
>>>>>> """Keep track that we want to for update of this"""
>>>>>> self._for_update_of = class_mapper(arg).mapped_table.name
>>
>>>>>> def _compile_context(self, labels=True):
>>>>>> context = super(MyQuery, self)._compile_context(labels)
>>>>>> if self._for_update_of:
>>>>>> context.statement = ForUpdateOf(context.statement,
>>>>>> self._for_update_of)
>>>>>> return context
>>
>>>>>> class ForUpdateOf(ClauseElement):
>>>>>> def __init__(self, statement, for_update_of):
>>>>>> self.statement = statement
>>>>>> self.for_update_of = for_update_of
>>
>>>>>> @compiles(ForUpdateOf)
>>>>>> def compile_forupdateof(element, compiler, **kw):
>>>>>> return "%s FOR UPDATE OF %s" %
>>>>>> (compiler.process(element.statement), element.for_update_of)
>>
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>>
>>
>
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