I don't know what you mean. is there SQL you know you want or is that the part
you want to figure out?
On Mon, Jul 1, 2019, at 4:21 PM, sector119 wrote:
> Mike, is it possible to load "@property" as subquery? Maybe as
> ARRAY[path_item, path_item, ...]
>
> воскресенье, 30 июня 2019 г., 20:26:42 UTC+3 пользователь Mike Bayer написал:
>>
>>
>> On Sun, Jun 30, 2019, at 5:37 AM, sector119 wrote:
>>> Nice, thanks a lot, Mike, now it works as expected
>>
>> that's great. the docs are not good here, there's not enough discussion of
>> "aliased()" , from_statement() and what they do, also I'm changing some
>> details of how they do their work for 1.4 in any case so documentation
>> efforts will be needed.
>>
>>
>>
>>>
>>> @property
>>> *def *path(self):
>>> session = object_session(self)
>>>
>>> *def *get_locality_path_q(locality_id):
>>> parent_q = session.query(Locality).filter(Locality.id ==
>>> locality_id).cte(recursive=*True*)
>>>
>>> parents = aliased(parent_q)
>>>
>>> locality_alias = aliased(Locality)
>>>
>>> q = parent_q.union_all(
>>> session.query(locality_alias).join(parents, locality_alias.id
>>> == parents.c.parent_id)
>>> )
>>>
>>> cte = aliased(Locality, q)
>>>
>>> *return *session.query(cte).order_by(cte.id)
>>>
>>> *return *get_locality_path_q(self.id)
>>>
>>> воскресенье, 30 июня 2019 г., 1:11:21 UTC+3 пользователь Mike Bayer написал:
>>>>
>>>>
>>>> On Sat, Jun 29, 2019, at 11:24 AM, sector119 wrote:
>>>>> Hello,
>>>>>
>>>>> I have Locality model with 'path' property to get path from 'root' of
>>>>> tree to current item, everything works ok, but
>>>>> I can't get result as Locality instance list..
>>>>> When I use
>>>>> *'*object_session(self).query(Locality).from_statement(q).order_by(Locality.id)'
>>>>> I get
>>>>> sqlalchemy.exc.ArgumentError: from_statement accepts text(), select(),
>>>>> and union() objects only.
>>>>>
>>>>> How can I adopt results to Locality model?
>>>>>
>>>>>
>>>>> *class *Locality(Base):
>>>>> __tablename__ = *'localities'
**
** *__table_args__ = {*'schema'*: SYSTEM_SCHEMA}
>>>>>
>>>>> id = Column(Integer, primary_key=*True*)
>>>>> parent_id = Column(Integer, ForeignKey(SYSTEM_SCHEMA +
>>>>> *'.localities.id'*))
>>>>> name = Column(UnicodeText, nullable=*False*)
>>>>> type = Column(Integer, nullable=*False*)
>>>>>
>>>>> @property
>>>>> *def *path(self):
>>>>> *def *get_locality_path_q(locality_id):
>>>>> top_q = select([
>>>>> Locality.id,
>>>>> Locality.parent_id,
>>>>> Locality.name,
>>>>> Locality.type,
>>>>> ]).\
>>>>> where(Locality.id == locality_id).\
>>>>> cte(recursive=*True*)
>>>>>
>>>>> parents = aliased(top_q)
>>>>>
>>>>> locality_alias = aliased(Locality)
>>>>>
>>>>> q = top_q.union_all(
>>>>> select([
>>>>> locality_alias.id,
>>>>> locality_alias.parent_id,
>>>>> locality_alias.name,
>>>>> locality_alias.type
>>>>> ]).select_from(join(locality_alias, parents,
>>>>> locality_alias.id == parents.c.parent_id))
>>>>> )
>>>>>
>>>>> *# return object_session(self).query(q).order_by(q.c.id)
** **return
*object_session(self).query(Locality).from_statement(q).order_by(Locality.id)
>>>>>
>>>>> *return *get_locality_path_q(self.id)
>>>>
>>>> above, "q" is a CTE, not a SELECT, meaning it's something you can select
>>>> FROM, like a table. Call select() to SELECT from it:
>>>>
>>>> return (
>>>> object_session(self)
>>>> .query(Locality)
>>>> .from_statement(q.select().order_by(q.c.id))
>>>> )
>>>>
>>>>
>>>> additionally, from_statement() does not allow further changes to the
>>>> statement and the ORDER BY must be in terms of thing you are selecting
>>>> from, in this case q.c.id
>>>>
>>>> your code would be easier if you made use of top_q as a FROM object rather
>>>> than a statement:
>>>>
>>>> lcte = aliased(Locality, q)
>>>>
>>>> return (
>>>> object_session(self)
>>>> .query(lcte)
>>>> .order_by(lcte.id)
>>>> )
>>>>
>>>>
>>>> There's not too many doc examples of how aliased() works with FROM clauses
>>>> but the basic idea is at:
>>>>
>>>> https://docs.sqlalchemy.org/en/13/orm/tutorial.html#selecting-entities-from-subqueries
>>>>
>>>> https://docs.sqlalchemy.org/en/13/orm/query.html#sqlalchemy.orm.aliased
>>>>
>>>> A little more on aliased() with CTE is written more for query.cte() which
>>>> you could also be using here:
>>>>
>>>> https://docs.sqlalchemy.org/en/13/orm/query.html?highlight=cte#sqlalchemy.orm.query.Query.cte
>>>>
>>>>
>>>>
>>>>
>>>>>
>>>>>
>>>>> --
>>>>> 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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>>>>>
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>>>>> For more options, visit https://groups.google.com/d/optout.
>>>>
>>>
>>> --
>>> 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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--
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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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