Select rows for update

SELECT ... FOR UPDATE creates a row-level lock on the returned rows until the transaction commits or rolls back. Other transactions executing a SELECT ... FOR UPDATE, UPDATE, or DELETE on those rows wait for the lock. How long they wait depends on the lock_timeout and statement_timeout settings. In the case of SELECT ... FOR UPDATE, the behavior can be customized using SKIP LOCKED and NOWAIT.

• SKIP LOCKED: Skips the locked rows as if they didn't match the criteria in the WHERE clause.
• NOWAIT: Throws an error immediately if any of the rows are locked.