You ought to be able to use the "sqlalchemy.func" system:
https://docs.sqlalchemy.org/en/14/core/tutorial.html#functions
server_default=sa.func.gen_random_uuid()
Hope that helps,
Simon
On Fri, Nov 19, 2021 at 6:21 AM [email protected]
<[email protected]> wrote:
>
> Tim,
>
> I wanted to offload the UUID generation for the PK to the server
> (server_default instead of just default argument). But I wasn’t able to find
> gen_random_uuid() documented in the PostgreSQL dialect, should probably be
> under Column Valued Functions?
>
> So I ended up using server_default=text("gen_random_uuid()")
>
> Is that the (currently) recommended way? It seems to work…
>
> Thanks!
> Jens
>
> On Thursday, January 4, 2018 at 7:50:21 AM UTC+10 [email protected] wrote:
>>
>> Thanks so much! Really appreciate the example.
>>
>>
>>
>>
>> On Wednesday, January 3, 2018 at 3:46:47 PM UTC-5, Mike Bayer wrote:
>>>
>>> On Wed, Jan 3, 2018 at 1:18 PM, Tim Chen <[email protected]> wrote:
>>> > Let's say I'm using a uuid PK for my models with a ` server_default` set
>>> > to
>>> > `gen_random_uuid()` (in PostgreSQL). Is there a way to ensure the
>>> > server_default value? I would like to catch any INSERT or UPDATE
>>> > statements
>>> > that set the PK value and raise an error if possible.
>>>
>>> Sure, I would use a before_cursor_execute() handler that does this.
>>> You can see the parameters and the statement coming in and raise an
>>> error if they have column values you don't want to see.
>>>
>>> http://docs.sqlalchemy.org/en/latest/core/events.html#sqlalchemy.events.ConnectionEvents.before_cursor_execute
>>>
>>> this is cleanest using some of the internal state of the context so
>>> here is a demo:
>>>
>>> from sqlalchemy import *
>>> from sqlalchemy.orm import *
>>> from sqlalchemy import event
>>> from sqlalchemy.ext.declarative import declarative_base
>>>
>>> Base = declarative_base()
>>>
>>>
>>> class A(Base):
>>> __tablename__ = 'a'
>>> id = Column(Integer, primary_key=True)
>>> x = Column(Integer)
>>>
>>> e = create_engine("sqlite://", echo=True)
>>>
>>>
>>> @event.listens_for(e, "before_cursor_execute")
>>> def receive_before_cursor_execute(conn, cursor, statement, parameters,
>>> context, executemany):
>>> if context.isinsert:
>>> table = context.compiled.statement.table
>>> for col in table.primary_key:
>>> if col.key in context.compiled.binds:
>>> raise TypeError("no pk allowed!")
>>>
>>>
>>> Base.metadata.create_all(e)
>>>
>>> s = Session(e)
>>> s.add(A(x=5))
>>> s.commit() # OK
>>>
>>> s.add(A(id=2, x=7))
>>> s.commit() # not OK
>>>
>>>
>>>
>>>
>>>
>>>
>>> >
>>> > --
>>> > 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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--
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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