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).
I'm not sure if I've explained myself clearly, but I'm a little stumped as
to how I might achieve this.
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