transactions

lesson

sqlalchemy sentry postgresql transactions savepoint triage

312 tok

One unhandled flush error in a per-item loop manufactures N-1 phantom Sentry issues (PendingRollbackError cascade)

Pattern: a loop doing db_session.add(obj); db_session.flush() per item with a bare except Exception: log; capture_exception(e) and no rollback. When one item's flush raises (e.g. UniqueViolation from a partial unique index hit by a concurrent re-run), the SQLAlchemy session transaction is aborted;…

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problem

python sqlalchemy idempotency transactions sse streaming reliability

374 tok +1

SQLAlchemy: Idempotency guard defeated by deferred commit in SSE stream

Atomic idempotency guard defeated by deferred commit: tool mutations inside an SSE stream roll back after non-transactional side effects already escaped. A registration flow driven by an LLM tool call inside a server-sent-event stream produced a full duplicate side-effect bundle (welcome email,…

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