On Tue, Aug 28, 2018 at 5:13 AM, Vikas Prasad
<[email protected]> wrote:
> Just in case someone stumbles upon it in future.
> I am using Postgres and I got the following results:
>
> # This worked:
> `the_sample.end_date = func.now()`
> `db.session.commit()`
>
> # This too worked:
> `setattr(the_sample, 'end_date', func.now())`
> `db.session.commit()`
>
> # This didn't work though:
> `Sample.query.filter_by(...).update({'end_date': func.now()})`
> `db.session.commit()`
>
> When using `Flask-SQLAlchemy` and setting `SQLALCHEMY=True`, the first two
> cases logs the `UPDATE` query followed by logging `COMMIT`. The last case
> didn't even logs the `UDPATE` query but directly logs a `ROLLBACK` with no
> other info.
>
> Not sure of underlying cause, just recording it so that someone from future
> saves some time.
the last one should definitely emit an UPDATE or it should be raising
an error. that you only saw a ROLLBACK suggests it raised an error and
your flask setup is suppressing the logging of that error.
>
> On Wednesday, June 15, 2016 at 8:10:30 PM UTC+5:30, Jean-Philippe Morin
> wrote:
>>
>> This is great! Thanks!
>>
>> On Wednesday, June 15, 2016 at 10:36:07 AM UTC-4, Mike Bayer wrote:
>>>
>>>
>>>
>>> On 06/15/2016 10:13 AM, Jean-Philippe Morin wrote:
>>> > (I am using PostgreSQL)
>>> >
>>> > I want to use the TIMESTAMP values of the SQL server machine instead of
>>> > the python `datetime.utcnow()` value of the WEB server machines.
>>> >
>>> > There could be latencies or time diffierences between machines, so I
>>> > would like to use the database server date and time as a common ground.
>>> >
>>> > Here is an example of what I would like to do:
>>> >
>>> > |
>>> > classSample(Base):
>>> > start_date
>>> > =Column('start_date',DateTime,server_default=func.now(),nullable=False)
>>> > last_update_date
>>> >
>>> > =Column('last_update_date',DateTime,server_default=func.now(),onupdate=func.now(),nullable=False)
>>> > end_date =Column('end_date',DateTime,nullable=True)
>>> >
>>> > |
>>> >
>>> > When the model is created, its `start_date` column is set to the
>>> > default
>>> > DateTime value of the SQL server by using `server_default=func.now()`.
>>> > Then, on every updates made on the model, its `last_update_date` is set
>>> > to the current DateTime value of the SQL server by using
>>> > `onupdate=func.now()`.
>>> >
>>> > |
>>> > defstart_acquisition():
>>> > new_sample =Sample()
>>> > # ... set sample columns ...
>>> > DBSession.add(new_sample)
>>> > DBSession.commit()
>>> >
>>> > defstop_acquisition(sample_id):
>>> > the_sample =DBSession.query(Sample).filter_by(...)
>>> > # ... set sample columns ...
>>> > the_sample.end_date =???
>>> > DBSession.commit()
>>> >
>>> > |
>>> >
>>> > How can I tell SQLAlchemy that on THAT particular update in
>>> > `stop_acquisition`, I want to set the `end_date` column to the
>>> > `func.now()` of the SQL server with the rest of the other modified
>>> > columns?
>>>
>>> just assign func.now() to it, it will render as that SQL expression in
>>> the UPDATE.
>>>
>>>
>>> http://docs.sqlalchemy.org/en/rel_1_0/orm/persistence_techniques.html#embedding-sql-insert-update-expressions-into-a-flush
>>>
>>>
>>>
>>>
>>> >
>>> > What would be the proper way of doing that? Is there something like an
>>> > `HybridProperty.expression` that could be used for inserts and updates?
>>> >
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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
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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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