【DM版本】:DM Database Server x64 V8 (--03134284094-20231220-212751-20067 Pack22)
【问题描述】*：层次查询执行时间较长，CNNTB_OPT_FLAG参数值已经是193，执行计划显示的代价很小，但实际执行时间很长，想请教一下该语句如何优化能提高执行效率呢

SELECT
        
        DECODE(newTable.SPECIALTYNAME, '', '未知', newTable.SPECIALTYNAME) SPECIALTYNAME,
        count(*) AS countNum
FROM
        (
                select  distinct
                        id,
                        regexp_substr(SPECIALTY_NAME, '[^,]+', 1, LEVEL) as SPECIALTYNAME
                from
                        POLITICAL_RESEARCH.SRSP_EXPERT_INFO
                where
                        status_code = '1' connect by LEVEL <= length(SPECIALTY_NAME) - length(regexp_replace(SPECIALTY_NAME, ',', '')) + 1
                order by
                        id
        ) AS newTable
WHERE
        1 = 1
GROUP BY
        newTable.SPECIALTYNAME