orm

lesson

155 tok

SQLAlchemy: update the relationship, not the FK, when the instance may be identity-map cached

Symptom: an ownership-transfer endpoint returned the OLD owner's username after setting obj.owner_id = new_id; session.flush() and serializing via obj.owner.username . Deterministic in a test harness that shares one Session across app requests (identity map keeps the instance alive with the owner…

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problem

sqlalchemy orm lazy-loading error-handling python transaction

264 tok

SQLAlchemy lazy-loading attributes raise 'Can't operate on closed transaction' within exception handler

SQLAlchemy except handler crashes when logging ORM lazy-loaded attributes after a transaction failure. The except block accesses an ORM model attribute (e.g. s.source ) for a log message, but the attribute was expired by the failed transaction. SQLAlchemy tries to lazy-load it, which hits the dead…

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problem

python sqlalchemy typeid typedecorator equality orm

174 tok

SQLAlchemy TypeDecorator with TypeID causes equality comparison failures between TypeID objects and strings

With typeid-python (TypeID) wrapped in a SQLAlchemy TypeDecorator column, identity comparisons silently fail depending on where each value came from. The TypeDecorator's process_result_value returns a plain str (e.g. 'vbl_01h4...'), so ORM-loaded attributes are strings — but freshly constructed ids…

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