tencent cloud

Feedback

Last updated: 2024-04-25 11:00:51

    Overview

    DDL statements support NO_WAIT and WAIT options. If a DDL statement with WAIT enabled fails to obtain an MDL lock, it will wait for WAIT seconds before it directly returns the query result. If a DDL statement with NO_WAIT enabled, it will directly return the query result without waiting for the MDL lock.
    SELECT FOR UPDATE statement supports NOWAIT and SKIP LOCKED options. If target rows are locked by another transaction, a SELECT FOR UPDATE statement is supposed to wait for the transaction to release the lock. But in some use cases like flash sales, you do not want to wait for a lock. You can use SKIP LOCKED to skip locked rows (as a result, the locked rows won't be returned in the query result set) or NOWAIT to return an error without waiting for the lock.
    Note that NO_WAIT and NOWAIT are different keywords.

    Supported Versions

    TDSQL-C for MySQL 5.7 (kernel version 2.0.23/2.1.9) or later.
    TDSQL-C for MySQL 8.0 (kernel version 3.1.10) or later.

    Use Cases

    Currently, DevAPI/XPlugin does not support using SKIP LOCKED or NOWAIT in SELECT FOR UPDATE/SHARE statements. Note that NO_WAIT in DDL statements and NOWAIT in SELECT FOR UPDATE statements are different keywords for historical reasons.
    
    
    Contact Us

    Contact our sales team or business advisors to help your business.

    Technical Support

    Open a ticket if you're looking for further assistance. Our Ticket is 7x24 avaliable.

    7x24 Phone Support