On Wed, Oct 11, 2023, at 11:10 AM, Pierre Massé wrote:
> Thanks a lot for the insight Mike,
>
> My question might then be quite naive: let's say I have a list of ORM
> entities on one side, and an accordingly sorted numpy array of computed
> features, how would I merge back attributes on entities?
>
> Let's say I have a list like :
> user_list = [User(id=1, dist=None), User(id=2, dist=None)]
>
> and a pandas DataFrame (or numpy array) like:
>
> dist_df =
> id dist
> 1 123
> 2 90
>
> How would I correlate those 2 into:
> [User(id=1, dist=123), User(id=2, dist=90)]
>
> Would the way to go be a simple for loop? Like:
> for user in user_list:
> user.dist = dist_df.loc[user.id, 'dist']
>
> Or is there something included in SQLAlchemy for this kind of task?
let's assume the two lists are ordered, which I would strongly recommend.
merge them with zip:
for user, dist in zip(user_list, dist_df):
user.dist = dist
>
> Regards,
>
> Pierre
>
> Le mer. 11 oct. 2023 à 15:07, Mike Bayer
> <mike_not_on_goo...@zzzcomputing.com> a écrit :
>> __
>>
>>
>> On Wed, Oct 11, 2023, at 4:22 AM, Pierre Massé wrote:
>>> Dear all,
>>>
>>> I have a requirement that makes me think that I need to "mass patch" some
>>> ORM objects. However, I am open to any suggestions regarding the way to
>>> answer my requirements.
>>>
>>> I have defined an ORM object which represents a user, holding longitude and
>>> latitude (among other attributes). At some point, I want to query many of
>>> those users, and send them back holding the geographical distance from a
>>> certain point (defined by longitude and latitude) along with their other
>>> data.
>>>
>>> Computing the distance is computationally heavy, and I noticed that I could
>>> greatly improve performance by mass computing those distances, using numpy
>>> for example.
>>>
>>> My question is: would it be possible to split my flow in 2 :
>>> - a flow that queries the data that is simply available in the database, as
>>> ORM entities
>>> - a flow that queries lon/lat as a numpy array, perform the distance
>>> computation
>>> and afterward merge those 2 in the queried ORM entities?
>>
>> This is a straightforward programming task. Query for the set of objects
>> you want, assemble the appropriate values into a numpy array, do wahtever
>> numpy thing you need, then merge back. you'd likely want to ensure you
>> can correlate numpy rows back to original objects most likely by keeping a
>> sort order between your result set and your numpy array.
>>
>> not stated here is if these numpy-calculated values as assembled onto ORM
>> objects are also database-column mapped, it sounds like they are not
>> (otherwise those values would be in the database), so the matrix values can
>> be applied to plain attributes on the objects directly.
>>
>> now where this may be more challenging, not sure if this is what you're
>> asking, is if you want this to happen implicitly for all queries or
>> something like that. there's ways to do this depending on the programming
>> patterns you are looking to achieve however I'd certainly start simple with
>> a function like "apply_lat_long_to_list_of_objects(obj)".
>>
>>
>>>
>>> It is important to me that I finally get back a list of ORM entities fully
>>> populated, because my whole downstream process is built around this
>>> assumption.
>>>
>>> Thanks a lot for your insights on the matter!
>>>
>>> Regards,
>>>
>>> Pierre
>>>
>>> PS: giving me a "SQLAlchemy fast distance computation" won't do the trick,
>>> because I have other kinds of computations that may not be optimizable this
>>> way.
>>>
>>>
>>> --
>>> 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.
>>> ---
>>> You received this message because you are subscribed to the Google Groups
>>> "sqlalchemy" group.
>>> To unsubscribe from this group and stop receiving emails from it, send an
>>> email to sqlalchemy+unsubscr...@googlegroups.com.
>>> To view this discussion on the web visit
>>> https://groups.google.com/d/msgid/sqlalchemy/CAH4TWVuJWP9WsSYNScPH%2BK9JJ3PqbOwxkm%3D_PXbPtYXzpBdvcg%40mail.gmail.com
>>>
>>> <https://groups.google.com/d/msgid/sqlalchemy/CAH4TWVuJWP9WsSYNScPH%2BK9JJ3PqbOwxkm%3D_PXbPtYXzpBdvcg%40mail.gmail.com?utm_medium=email&utm_source=footer>.
>>
>>
>>
>> --
>> 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.
>> ---
>> You received this message because you are subscribed to the Google Groups
>> "sqlalchemy" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
>> email to sqlalchemy+unsubscr...@googlegroups.com.
>> To view this discussion on the web visit
>> https://groups.google.com/d/msgid/sqlalchemy/f7dcbd42-0509-46c5-b668-1a15a4834cab%40app.fastmail.com
>>
>> <https://groups.google.com/d/msgid/sqlalchemy/f7dcbd42-0509-46c5-b668-1a15a4834cab%40app.fastmail.com?utm_medium=email&utm_source=footer>.
>
>
> --
> 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.
> ---
> You received this message because you are subscribed to the Google Groups
> "sqlalchemy" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to sqlalchemy+unsubscr...@googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/sqlalchemy/CAH4TWVtgCh%2Bi3H2rF2js5rLsOSwfE%3DZF_zA%2BVxy03_iy-ab7NA%40mail.gmail.com
>
> <https://groups.google.com/d/msgid/sqlalchemy/CAH4TWVtgCh%2Bi3H2rF2js5rLsOSwfE%3DZF_zA%2BVxy03_iy-ab7NA%40mail.gmail.com?utm_medium=email&utm_source=footer>.
--
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.
---
You received this message because you are subscribed to the Google Groups
"sqlalchemy" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to sqlalchemy+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/sqlalchemy/052a4fc8-22b5-4acd-afdc-49adcbc924df%40app.fastmail.com.
