hard20 pts · first answer countspostgresqlconcurrencymessage-queues

Workers block each other on a jobs table

Ten workers each run SELECT ... FROM jobs WHERE status = 'pending' ORDER BY id LIMIT 1 FOR UPDATE. They end up waiting on the same row and process jobs one at a time. What fixes this?

A.Add SKIP LOCKED, so each worker skips rows other workers have locked and takes the next free jobB.Switch the workers' transactions to SERIALIZABLE isolation so the database hands each worker a different rowC.Drop FOR UPDATE and rely on updating status afterwardsD.Run LOCK TABLE jobs at the start of each worker transaction

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