pessimistic locking
Lock the protected rows before making a competing update.
Use this when Several workers try to claim the same job or modify the same inventory row.
without the term
“Two workers must not claim the same record. Hold the necessary lock while deciding and changing it.”
with the term · How do you ask a model for pessimistic locking?
Use pessimistic row locking for this update. Keep the decision in one transaction and test two concurrent writers.
What is pessimistic locking?
Pessimistic concurrency uses locks to prevent conflicting operations while a transaction makes its decision. In PostgreSQL, SELECT FOR UPDATE locks selected rows until the transaction ends.
Why does pessimistic locking matter when vibe coding?
An agent can read a value, release the transaction, and then perform the supposedly protected write.
How do you do pessimistic locking?
Keep read, decision, and write inside one transaction. Lock the necessary rows in consistent order. Test two competing sessions and lock timeouts.
What goes wrong with pessimistic locking?
Locking existing rows does not automatically protect every predicate or a missing row; constraints or stronger isolation may be needed.
Sources for this entry
- PostgreSQL: Explicit locking
Row and table locks, blocking, deadlocks, and consistent acquisition order.
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