ps_is_thread_instrumented()

• 在threads表中检查指定线程是否启用了监控功能，给定参数值对应threads表中的PROCESSLIST_ID列或SHOW PROCESSLIST输出的Id列值

  • 如果给定连接ID值在threads表中未查询到，则返回UNKNOWN值，如果给定ID值为NULL则返回NULL

• 参数：

  • in_connection_id BIGINT UNSIGNED：连接ID。对应performance_schema.threads表中的PROCESSLIST_ID列值或SHOW PROCESSLIST输出的Id列值

• 返回值：一个ENUM('YES','NO','UNKNOWN')值

• 定义语句

DROP FUNCTION IF EXISTS ps_is_thread_instrumented;

DELIMITER $$

CREATE DEFINER='root'@'localhost' FUNCTION ps_is_thread_instrumented (
        in_connection_id BIGINT UNSIGNED
    ) RETURNS ENUM('YES', 'NO', 'UNKNOWN')
    COMMENT '
            Description
            -----------

            Checks whether the provided connection id is instrumented within Performance Schema.

            Parameters
            -----------

            in_connection_id (BIGINT UNSIGNED):
              The id of the connection to check.

            Returns
            -----------

            ENUM(\'YES\', \'NO\', \'UNKNOWN\')

            Example
            -----------

            mysql> SELECT sys.ps_is_thread_instrumented(CONNECTION_ID());
            +------------------------------------------------+
            | sys.ps_is_thread_instrumented(CONNECTION_ID()) |
            +------------------------------------------------+
            | YES                                            |
            +------------------------------------------------+
            '

    SQL SECURITY INVOKER
    NOT DETERMINISTIC
    READS SQL DATA
BEGIN
    DECLARE v_enabled ENUM('YES', 'NO', 'UNKNOWN');

    IF (in_connection_id IS NULL) THEN
        RETURN NULL;
    END IF;

    SELECT INSTRUMENTED INTO v_enabled
      FROM performance_schema.threads
    WHERE PROCESSLIST_ID = in_connection_id;

    IF (v_enabled IS NULL) THEN
        RETURN 'UNKNOWN';
    ELSE
        RETURN v_enabled;
    END IF;
END$$

DELIMITER ;

• 参考链接：https://dev.mysql.com/doc/refman/5.7/en/sys-ps-is-thread-instrumented.html

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