[ocp0531] 答复: [ocp0531] 关于index options
- From: "Jianjun Li" <4.4bsd.lite@xxxxxxxxx>
- To: <ocp0531@xxxxxxxxxxxxx>
- Date: Tue, 30 Jun 2009 13:54:50 +0800
字面上的意思是，反键索引是以相反的键值顺序存储
Reverse Key indexes spread the distribution of index
updatees across the index tree by reversing the data value
of the index key .
It's only useful for queries that contain equality
predicates .
Because lexically adjacent keys are not stored next to
each other in a reverse key index , For every updation
, Oracle need to search the whole index , it takes
more time than normal B-tree index
其中一个用途是用正键索引可以用在诸如’abc%’这种查询
使用反键索引可以用在诸如’%abc’这类查询
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发件人: ocp0531-bounce@xxxxxxxxxxxxx [mailto:ocp0531-bounce@xxxxxxxxxxxxx]
代表 陈旭
发送时间: 2009年6月29日 22:03
收件人: ocp0531
主题: [ocp0531] 关于index options
李老师，书上有句话A reverse key index has its key value bytes stored in
reverse order.
这话不是很理解。。。能举个例子说明下么？
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