oracle递归查询性能优化,请教这个递归查询如何优化

我的一个递归查询如下,递归查询的表也就1000多行,但执行出来却花了240多秒,请教下怎么优化!!!

select distinct mtt.taskitem_id

from security_taskitem mtt,

(

select mrt.task_id

from security_userrole mur,

security_role mrt

where mur.user_id &＃61; 2

and mur.role_id &＃61; mrt.role_id

) temp

connect by mtt.task_id &＃61; prior mtt.taskitem_id

start with mtt.task_id in(temp.task_id)

执行计划

SELECT STATEMENT, GOAL &＃61; CHOOSE

SORT UNIQUE

CONNECT BY WITHOUT FILTERING

COUNT

NESTED LOOPS

NESTED LOOPS

TABLE ACCESS FULL                SECURITY_USERROLE

TABLE ACCESS BY INDEX ROWID        SECURITY_ROLE

INDEX UNIQUE SCAN        PK_SECURITY_ROLE

TABLE ACCESS FULL        SECURITY_TASKITEM