Use savepoints when retrying to take AccessShareLock. #401
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In lock_access_share() function, before acquiring an AccessShareLock on the target table, concurrent DDL commands are terminated unconditionally. However, there is a window between this termination and the actual "LOCK TABLE ... IN ACCESS SHARE MODE" operation, allowing other DDL commands to run on the target table. If the LOCK TABLE failed due to a lock conflict, the transaction was rolled back and retried to execute LOCK TABLE, but the LOCK TABLE command could not be executed again as the transaction had already closed. This commit fixes the issue by using SAVEPOINT and ROLLBACK TO SAVEPOINT so that we can retry to take a lock in the same top transaction. Issue reorg#383
za-arthur
approved these changes
May 20, 2024
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Thank you for reviewing the change! Merged. |
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In lock_access_share() function, before acquiring an AccessShareLock on the target table, concurrent DDL commands are terminated unconditionally. However, there is a window between this termination and the actual "LOCK TABLE ... IN ACCESS SHARE MODE" operation, allowing other DDL commands to run on the target table. If the LOCK TABLE failed due to a lock conflict, the transaction was rolled back and retried to execute LOCK TABLE, but the LOCK TABLE command could not be executed again as the transaction had already closed.
This commit fixes the issue by using SAVEPOINT and ROLLBACK TO SAVEPOINT so that we can retry to take a lock in the same top transaction.
Issue #383