1、查询sql在不加order by的情况下查询速度特别快，加order by之后查询不走联合索引
2、EXECUTION_ID，ACT_ID，ACT_ID 三个列有联合索引

SELECT
	*
FROM
	(
	SELECT
		 a.*,
		ROWNUM rnum
	FROM
		(
		SELECT
			RES.*
		FROM
			HBGWYCJGPT.BPM_ACT_HI_ACTINST RES
		WHERE
			RES.EXECUTION_ID_ = '908259790449549312'
			AND RES.ACT_ID_ = 'hussar_2'
			AND RES.END_TIME_ IS NULL
		ORDER BY --添加order by
			RES.ID_ ASC ) a
	WHERE
		ROWNUM < 10)
WHERE
	rnum >= 0

SELECT
	*
FROM
	(
	SELECT
		 a.*,
		ROWNUM rnum
	FROM
		(
		SELECT
			RES.*
		FROM
			HBGWYCJGPT.BPM_ACT_HI_ACTINST RES
		WHERE
			RES.EXECUTION_ID_ = '908259790449549312'
			AND RES.ACT_ID_ = 'hussar_2'
			AND RES.END_TIME_ IS NULL
			RES.ID_ ASC ) a   -- 不添加order by
	WHERE
		ROWNUM < 10)
WHERE
	rnum >= 0

添加并行的情况下也特别快


并行2的情况下也不会走联合索引

问题分析：ORDER BY ID列不在联合索引中，所以没有走联合索引，可以将id列添加到原有的联合索引。