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    PolarDB:How to customize the SQL timeout period

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    PolarDB:How to customize the SQL timeout period

    Last Updated:Mar 28, 2026

    PolarDB-X provides custom HINT statements that you can use to modify the SQL timeout period.

    PolarDB-X applies a default timeout of 900 seconds to SQL statements sent from compute nodes to storage nodes. For slow SQL statements that legitimately need a longer execution window, use the SOCKET_TIMEOUT hint to set a per-statement timeout.

    Usage notes

    • PolarDB-X hints support two formats: /*+TDDL:hint_command*/ and /!+TDDL:hint_command*/.
    • When using the /*+TDDL:*/ format in the official MySQL command-line client, add the -c flag at login. Without -c, the client strips PolarDB-X hints — before sending statements to the server. For details, see MySQL comments and mysql client options.

    Syntax

    /*+TDDL:SOCKET_TIMEOUT(time)*/

    Specify time in milliseconds.

    Example

    Set a 40-second timeout for a SELECT statement:

    /*+TDDL:SOCKET_TIMEOUT(40000)*/SELECT * FROM t_item;
    Important A longer timeout keeps database resources occupied for the full duration of the statement. If many long-running SQL statements run concurrently, resource exhaustion can degrade PolarDB-X availability. Optimize long-running SQL statements rather than relying on extended timeouts.