That's a cool idea, but it would need to reference the instance we've created to use the `id` atribute.
ie the sql would be `select max(version)+1 from responses where id = :id` On Friday, 18 November 2016 14:39:52 UTC, Mike Bayer wrote: > > > > On 11/18/2016 09:10 AM, Alexander O'Donovan-Jones wrote: > > I'm currently working on using the ORM features of sqlalchemy with a > > legacy database table. The table can be roughly described like this: > > > > class APIResponse(Base): > > __tablename__ = 'responses' > > id = Column(Text, primary_key=True) > > version = Column(Integer, primary_key=True) > > payload = Column(JSONB, nullable=False) > > created_at = Column(DateTime, nullable=False) > > > > > > The table stores JSON payloads where the primary key is determined by > > the combination of the id and version columns (as a composite primary > > key). What I'm trying to work out is whether it's possible to have the > > value of the version column be the result of > > func.max(APIResponse.version) + 1, that is, MAX()+1 to increment the > > version. > > > > This is running on Postgresql, and so I took a look at the sequence > > support, but that appears to be a table wide sequence, and not keyed off > > a value (ie: I couldn't have 10000 id's each mapping to a sequence to > > generate versions). > > > you can set any SQL expression you want for a default, some examples at > https://docs.sqlalchemy.org/en/latest/core/defaults.html#sql-expressions. > This would look like default=select([func.max(API.response.version) + > 1]). hope that helps. > > -- 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 post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
