查看数据库中有无多余的索引，即一个索引的字段为另一个索引的前几个字段。如index1的定义为test(filed1,filed2),index2的定义为test(filed1,filed2,filed3)，则认为index1是多余的。(摘自Ixora)
column redundant_index format a39
column sufficient_index format a39
select /*+ ordered */
o1.name||'.'||n1.name redundant_index,
o2.name||'.'||n2.name sufficient_index
from
(
select
obj#,
bo#,
count(*) cols,
max(decode(pos#, 1, intcol#)) leadcol#
from
sys.icol$
group by
obj#,
bo#
) ic1,
sys.icol$ ic2,
sys.ind$ i1,
sys.obj$ n1,
sys.obj$ n2,
sys.user$ o1,
sys.user$ o2
where
ic2.obj# != ic1.obj# and
ic2.bo# = ic1.bo# and
ic2.pos# = 1 and
ic2.intcol# = ic1.leadcol# and
i1.obj# = ic1.obj# and
bitand(i1.property, 1) = 0 and
ic1.cols * (ic1.cols + 1) / 2 =
( select
sum(xc1.pos#)
from
sys.icol$ xc1,
sys.icol$ xc2
where
xc1.obj# = ic1.obj# and
xc2.obj# = ic2.obj# and
xc1.pos# = xc2.pos# and
xc1.intcol# = xc2.intcol#
) and
n1.obj# = ic1.obj# and
n2.obj# = ic2.obj# and
o1.user# = n1.owner# and
o2.user# = n2.owner#
/
