On Wed, Aug 24, 2022, at 6:32 AM, Evgenii wrote:
>
> Thank you one more time!
> Just in case I leave fixed expression here:
>
> `session.execute(
> select(Instance).where(Instance.id.in([list_of_ids])),
> execution_options={"populate_existing": True}
> )
`
> Is there any way to set populate_existing = True for engine or sessionmaker?
>
not right now, there is an issue to maybe have session-wide execution options.
the option can be set on an engine but I'm not sure it takes effect for the
ORM when set only at the engine level.
>
> вторник, 23 августа 2022 г. в 22:34:23 UTC+3, Mike Bayer:
>>
>>
>> On Tue, Aug 23, 2022, at 3:00 PM, Evgenii wrote:
>>>
>>>
>>> Thanks a lot!
>>> I used “vectorized” for sqlalchemy.orm.Session.refresh method and mean that
>>> it would be nice to use:
>>>
>>>
>>> `session.refresh(instances_list)
`
>>> that make a single query to database. Instead of:
>>>
>>
>>
>> do this:
>>
>> session.execute(
>> select(Instance).where(Instance.id.in
>> <http://instance.id.in/>([list_of_ids]),
>> execution_options={"populate_existing": True})
>> )
>>
>> all objects refreshed
>>
>>
>>
>>>
>>> `for el in instances_list:
>>> session.refresh(el)
`
>>> that make N queries.
>>>
>>> like:
>>>
>>> `res = session.query(InstrumentTable).filter(InstrumentTable.id.in_([id1,
>>> id2, ..., idn])).all()
>>> *# and sort res with given ids order*
`
>>> is much faster than (especially in low network connections):
>>>
>>> `instuments = [session.query(InstrumentTable).get(id_) *for* id_ *in* [id1,
>>> id2, ..., idn]]
`
>>>
>>> вторник, 23 августа 2022 г. в 21:04:05 UTC+3, Mike Bayer:
>>>>
>>>>
>>>> On Tue, Aug 23, 2022, at 1:50 PM, Evgenii wrote:
>>>>> Hi there!
>>>>>
>>>>>
>>>>>
>>>>> Please help me to understand:
>>>>> I want to make two equal queries, that sends real queries to database
>>>>> each time:
>>>>>
>>>>>
>>>>> `session.query(InstrumentTable).get(instr_id)
>>>>> <some other code>
>>>>> session.query(InstrumentTable).get(instr_id)
`
>>>>>
>>>>>
>>>>> The problem is that second query returns instance from identity_map.
>>>>> I know how to hardcode it, but I want a beautiful solution.
>>>>>
>>>>>
>>>>> 1. No, I cannot use refresh method, because it is not vectorized
>>>>> (this part of code is used in custom vectorized refresh method,
>>>>> because in our case each transaction is slow and therefore expensive) -
>>>>> having vectorized SA refresh is a perfect solution, but it does not exist.
>>>>
>>>> "vectorized". googled it, seems to mean "Vectorization is the process of
>>>> converting an algorithm from operating on a single value at a time to
>>>> operating on a set of values at one time. " OK. which would mean that
>>>> get() is also not "vectorized" since it also operates on one value at a
>>>> time...so..not really sure what that means.
>>>>
>>>> Anyway, don't use query.get(), use session.get() and pass populate_existing
>>>>
>>>> https://docs.sqlalchemy.org/en/14/orm/session_api.html?highlight=session+get#sqlalchemy.orm.Session.get
>>>>
>>>> session.get(InstrumentTable, id, populate_existing=True)
>>>>
>>>>
>>>>
>>>>
>>>>>
>>>>> 1. rollback make real second query, but it seems to be hardcode.
>>>>> 2. session.identity_map._dict = {} hardcode too
>>>>> 3. Opening another session hardcode too.
>>>>> 4. Using one of AUTOCOMMIT, READ COMMITTED, READ UNCOMMITTED,
>>>>> REPEATABLE READ, SERIALIZABLE as isolation_level seems to be a true way,
>>>>> but none of them does not work as I expect.
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> 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
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>>>>
>>>
>>>
>>> --
>>> SQLAlchemy -
>>> The Python SQL Toolkit and Object Relational Mapper
>>>
>>> http://www.sqlalchemy.org/
>>>
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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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