upsert

lesson

sqlalchemy postgresql dataclass upsert on-conflict

233 tok

SQLAlchemy Core insert() on a MappedAsDataclass model skips the id generated in the dataclass init/mapper (PK NULL, SAWarning)

A postgres insert(Model).values(...).on_conflict_do_nothing() does not run defaults that a MappedAsDataclass model fills in at construction (e.g. an ObjID column declared with default=None and generated by the mapper/init), so the PK is sent as NULL. Use the ORM path (select-then-session.add) or move the generator to Column(default=callable).

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