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全部话题 - 话题: index
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t***s
发帖数: 48
1
【 以下文字转载自 CS 讨论区 】
发信人: truss (truss), 信区: CS
标 题: 【求教】Text Indexer for Large Volume of ASCII files【先谢】
发信站: BBS 未名空间站 (Wed Oct 17 14:02:57 2012, 美东)
我需要index大概四百万个ascii文件。哪位高人给推荐个好用的text indexer。多谢。
简单的说,就是个类似于text search engine里面indexer那一部分,但是提供比较方
便的command line access。最好在windows上。
具体点,就是能够index这四百万文件,把结果放在一个可以从command line方便读取
的repository里。可以是relational database或者其他proprietary的格式,只要能够
从command line或者perl之类的scripts读,结果能输出到ascii文件就可以。当然如果
可以从数据库里直接用SQL读更好。
安装越简单越好。最好都是command line。
我试过微软的sear... 阅读全帖
w********h
发帖数: 12367
2
来自主题: Biology版 - 要是饶毅H-index真的只有34...
我不知道其他生物部候选人的资历,
但显然这个H-index大大低于他的名气,至少低于我先前的感觉。
前面还有人说什么田禾都进了,饶毅自然不会屑于参与。
要知道现在化学部的院士候选人基本上都已经
文章数〉200;H-index > 35;citation 〉5000了,
田禾的数字应该是320, 39, >6000.
生物么,本来做的人就多,除了文章数量上比不上化学类,
H-index和citation都应该高一些才是。
经我自己查了查,
饶毅文章总数〈80,H-index < 35,citation < 4000。
虽然发表的杂志确实比较高档,
但如果文章质量好再加上杂志吸引眼球多,
理应在H-index和citation上有更好成绩,
可惜被引最高的一片也不过319次而已。
更何况,国内院士还不完全靠文章,
还要看国家三大奖的获得情况和大项目(863,973,etc)的主持情况,
(你可以尽情鄙视,但它们是中国特色的指标)
以及在所在领域的培养人才上的贡献。
这些也就造成了国内科研体制对海龟资历上的一种天然排斥。
所以我感觉,
饶毅现在进不了这一轮,
也没什么奇怪的,
牢骚私自发... 阅读全帖
a**r
发帖数: 224
3
来自主题: Chemistry版 - H index 之后,又来了个 Wu index
According to Wu, a researcher with a w-index of 1 or 2 is someone who "has
learned the rudiments of a subject". A w-index of 3 or 4 characterizes a
researcher who has mastered “the art of scientific activity”, while "
outstanding individuals" are those with a w-index of 10. Wu reserves the
accolade of "top scientists" to those with a w-index of 15 after 20 years or
20 after 30 years.
太油菜了
z*******n
发帖数: 1034
4
来自主题: MobileDevelopment版 - Cost per App Launch Index&Cost per Install: March 2014
The Cost per App Launch Index tracks the cost of each repeat app launch over
time, which focuses on engagement and life-time value of mobile users. In
March, the Android Index dropped 5 percent to $0.10 –a 37 percent decrease
year-over-year; and the iOS Index decreased 10 percent to $0.17 – up 2
percent year-over-year.
Cost per Install (CPI) Index: March 2014
The Cost per Install (CPI) Index measures the cost per app install directly
attributed to advertising. In March, the CPI for iOS saw a sli... 阅读全帖
s***z
发帖数: 631
5
菌斑的大牛有知道的吗?
【 以下文字转载自 Living 讨论区 】
发信人: stxyz (xy), 信区: Living
标 题: 哪里能测量眼镜镜片的指数(index)
发信站: BBS 未名空间站 (Thu Dec 3 16:53:44 2015, 美东)
有点中/高度近视,现有的眼镜是普通树脂的(polycarbonate)的。于是配新眼镜的时
候就订了high index的。
结果取回来发现新的镜片不比就的薄(而新旧镜框大小形状是几乎一样的,新镜片度数
实际上还低了一点点)。
回到眼镜店。optician坚持说如果做镜片的过程出错那么做镜片的人就会有大麻烦,所
以不可能出错。并且说high index的主要目的是看的更清楚,而不是更薄。
请问谁知道哪里可以确认/测量镜片的index吗?
w********h
发帖数: 12367
6
来自主题: Faculty版 - 有个做faculty H-index的指标
这种事情还要经过审稿人和编辑一关。
而且H-index是回顾性的,要和citation/paper number综合考虑。
well-recognized ---> high index.
if well-recognized ---> low index, then a big why arises.
if high index but not well-recognized, then H does not count at all.
h********0
发帖数: 12056
7
来自主题: Faculty版 - H-index 的传说
一般来说美国科学院院士的 h-index 都很高,H-index 达到 60以上,你就是
差不多院士水平了。这里说明院士通常资源多,打工的多,学生和薄后平均水平高。
诺奖获得者 h-index 往往没有院士(平均)高,但是单篇引用通常极高。 极端的例子
是2013获奖 的Peter Higgs, h-index 只有十几。这是个人英雄主义,
美国现行体制越来越不支持这种风格,学校就是反复让大家合作,多写 proposal,
多拿钱。
n****i
发帖数: 1772
8
来自主题: Investment版 - 讲讲index fund 的优缺点,呵呵
很简单。
优点:
1). Low cost. Index fund的expense ratio 在0.2%, MFs的平均expense ration是1.
36%.
2). 简单。半年或一年看一次就行了。
3). turn over小,少交税。
缺点:
1). No way to out-perform, 扣掉cost, 你的回报比市场只小一点,很接近啦。依然
逃不掉市场崩溃的风险。想像
你买了index fund when nasdaq is at 6xxx.
2). a little bit extra small cost: index fund 要买掉被delisted的股票(价格在
跌),买如新加进来的股票(价格
高)
下面我要说的很重要啊,大家要记笔记了!
“Economists cite the efficient market theory as the fundamental premise
that justifies the creation of
the index funds. The theory states that fund managers an
s******d
发帖数: 323
9
来自主题: Investment版 - [合集] index fund一样make mistake
☆─────────────────────────────────────☆
starwood (star^wood) 于 (Tue Feb 13 14:41:35 2007) 提到:
而且是100%肯定会make mistake. why?
market cap weighted index = chase performance.
什么涨得快,index里面什么就多。看看2000年S&P500里有多少tech bubble股。
7年之后,it又变成了value investor了。hehe.
这个错误有多大姑且不说,说投资index fund没有mistake我不同意。
☆─────────────────────────────────────☆
hobbes (calvin) 于 (Tue Feb 13 15:27:50 2007) 提到:
其实最可怕的还是没有原则。今天index,明天active manage,今天buy & hold,明天
active rebalance......
☆────────────────────────────────
t***s
发帖数: 163
10
来自主题: Investment版 - [原创]Index investing思辩未名版之一
偶出于服务new cop的目的,疯狂打字一晚,版主mark一个,看客送个包子吧,呵呵
1. Index investing不是个人投资中最重要的问题
对,你没有看错,“不是”最重要的问题!
最重要的是:
Asset allocation
Buy and hold for long term
Low cost
没有上面三条,一切免谈
如果你做到上面三条,但是用了active managed fund,请放我一马,咱们下次再讨论
2. 对大多数散户投资者而言,index investing是达成投资目标的最佳方式
看清我的限定词
大多数 = 80%以上(你可能不是,你完全可以选择其它方式 )
散户投资者 = 不是以金融分析为职业的个人投资者(aka大多数investment版读者)
达成投资目标 = 养老,孩子上大学(而非getting rich quickly)
最佳方式 = 结论是压倒性的,没有其它方式超过它
所以并不是笼统地说index investing是所有投资style中最好的
而是说,“对大多数散户投资者而言”是“最好的”
3. 什么是index investing
以mar
s*******d
发帖数: 126
11
来自主题: Investment版 - 请教一下INDEX FUND,多谢
I'd go with Vanguard index funds. Although the Spartan (Fidelity) index
funds have lower expense ratio than corresponding Vanguard index funds (
Fidelity might be losing money to run these funds to attract customers),
their funds are not as tax efficient as the Vanguard funds. You can google
and people have compared them. For your son who is going to be in the market
for many many years, tax efficiency is a concern.
Within the Vanguard family, Total Stock Market Index Fund (VTSMX) maps the
entir
m******m
发帖数: 535
12
indexer们啊,fidelity有没有什么可以推荐的index fund啊
我现在只看到
Spartan U.S. Equity Index Fund - Investor Class(FUSEX)
Spartan 500 Index Fund - Investor Class(FSMKX)
有什么区别啊?
s*******d
发帖数: 126
13
来自主题: Investment版 - not all index (500) funds are created equal
it's a misconcept that all S&P 500 index funds perform equally (minus the ER
). You shouldn't just look for lower fees, there are at least two other
factors that I know of can impact long term performance of index funds. One
is tax efficiency (that is related to how often the index funds buy and sell
stocks) and tracking errors (how closely the fund is tracking the
corresponding index). Obviously the former matters less if you have the
funds in a tax-deferred account, the latter is important reg
c**B
发帖数: 219
14
index和actively managed funds的区别比较好理解
但是ETF和一般的index又有什么区别呢?
我以前一直以为这两个是一样的 今天才知道ETF是index的一种,似乎和traditional
index funds又有些不同
还请牛人给指点一下
如果每次买一点点(千把块钱)一抱抱三五年,更适合哪个呢?
S**C
发帖数: 2964
15
来自主题: Investment版 - 80% active MM lose to index....what 80%?
It is ironic that bogleheads brought up such cliche that 80% (or whatever
percentage) MM lose to index and at the same time use market-cap weighted
index.
What about AUM weighted active MM performance? I am sure the index will
still has tiny little edges, but the margin will be significantly smaller.
How about throw out high-fees and closet index funds? Vangaurd's active
funds anyone?
An average Joe trained tennis for a few days can say his tennis skill is
better than 80% or maybe 90% world popu... 阅读全帖
a*******t
发帖数: 867
16
来自主题: Investment版 - 有谁研究过Small-cap Index ?
这里有各Index 的收益表。有3个问题请教:
1。 这些年收益是否包含了Dividend,还是仅仅是Index的变化?
2。 1998年的经济格局是啥?Small-Cap 跟其他的 Index比较差了非常多。
3。 2000和2001年有经济危机。但是Small-cap 的表现比其他Index 的都好
很多。难道这意味Small-cap 更能抗跌?当然2007年Small-cap的表现就差很多了.
http://www.bogleheads.org/wiki/Small_Cap_Index_Returns
Thanks
a*******t
发帖数: 867
17
来自主题: Investment版 - 有谁研究过Small-cap Index ?

There are links to other index, like Mid-cap, Large, Mega, and Total. The
links are on the right of the page.
If you pull all index of different Size together you will notice that 1998
is a strange year when Small-Cap index is way too low compared to Mid- or
Large-cap index.
And in 2000 and 2001 the trend was reversed.
w******1
发帖数: 154
18
来自主题: Investment版 - index funds to vanguard 2045
I have several index funds, and two of them have redemption rate, so I can't
change them. I want to change the other index funds to vanguard 2045.
Should I just change the percentage of the investment? for the two index
funds that have redemption rate, the percentage should be the same? For
further contributions, the total amount of each fund will increase. As long
as the percentage is the same as before, the index funds will not charge the
redemption rate, right?
m**x
发帖数: 8454
19
yeah. or you can buy total market index fund which include 500 and all
others. or you can buy index fund with any combinations below:
large cap, middle cap, small cap vs. value, blend, growth
s&p 500 is kind of large cap blend; while total market include all caps,
but is still classified as large blend since 500 large cap companies are
included. There is also extended market index which simply excludes the 500,
and is therefore classified as middle cap blend.
you can also choose to buy do... 阅读全帖
r****m
发帖数: 1204
20
来自主题: Investment版 - 为什么短期投资不适宜买index fund?
如果是短期"投资", 那意味着你这钱短期内会有它用, 但已经有历史数据在那里了,
index funds 短期也可能跌得能多的, 你能承受吗? 如果不能, index funds don'
t work for you.
如果这钱短期内也无它用, 但你实际上想做的是短期"炒作", 那index funds也不合
适, individual stocks更合适。
In summary, index funds are not for short terms.
s*********f
发帖数: 530
21
ER是0.32%
这个算高吗?
我们单位的退休账户被一家公司垄断了,他们的target fund 2045 asset里面index
fund的比例不高(33%),剩下的非index fund不但比例高,而且表现平平。所以我在考
虑要不要全换成自己配的index fund(80%stocks, 20%bond)
如果换的话,是不是等于卖掉我现在持有的target fund,然后再购入各个index fund
?如果timing不对,很可能会亏一笔?因为好像大部分人都建议buy and hold, do NOT
trade.
问题很初级,让诸位见笑了。再次谢过
P*****e
发帖数: 313
22
来自主题: Investment版 - 关于买 total world stock index
我看Elements of investing书上写的,新手做长期投资可以从US stock index开始,
然后过渡到international stock index。可能是因为international stock index的风
险比US stock index的风险要大。
E******w
发帖数: 2616
23
来自主题: Investment版 - 关于buy&hold index fund
我没有混淆。9段高手也有下模仿棋的,那也是主动选择的策略之一。但是9段高手这么
下,绝对不会是单纯的模仿,而是在等待机会。
模仿棋和buy&hold index一样,核心是采取一个保守策略。在看不清楚或者对自己与市
场搏杀的能力没有信心的前提下,保证拿到average return。但是,要记住,hold
index,你永远只是average。不能说着说着就自我感觉above average了。敢自称"高手
"的,至少都是认为自己是above average的。这个title和主动选则average return的
策略是矛盾的。因此我认为坚定hold index的,至少不能算高手。
我并不那么反对buy & hold index。人贵在有自知之明。就算是能做market timing,
也不是任何时刻任何环境下都能做到above average的。在看不清的时候退回average的
策略本来就是常用手法。不过愿意认真研究的,一般不会满足于average。我反对的是
把一个average的策略吹成圣典,搞得好像这是高手中的高手一样。这是华尔街希望大
家相信的。不是average策略本身... 阅读全帖
o*****n
发帖数: 2098
24
来自主题: Postdoc版 - 查过你的文章h-index吗?
H-index就是你有x篇文章被引用了x次以上,x的最大值就是你的H-index。如果你只有
一篇文章,被引了100000次,你的H-index还是1. 和平均每篇引用不同,多发垃圾文章
对H-index没有影响。
z*********z
发帖数: 163
25
By Kathleen Madigan
http://blogs.wsj.com/economics/2010/09/07/index-points-to-slowdown-in-hiring/
An August measure of labor indicators suggests a slowing in hiring in coming
months, according to a report released Tuesday by the Conference Board.
The board said its August employment trends index fell to 96.7, down from
July’s revised figure of 97.4, first reported as 97.0. The August index is
up 9.4% from a year ago.
“Employment growth has been slow lately, and the employment trends index
sugges
P*********g
发帖数: 1336
26
【 以下文字转载自 PhotoGear 讨论区 】
发信人: Pigblackdog (俺是农民), 信区: PhotoGear
标 题: 万佛-什么是Index Annuity,值得投资吗?
发信站: BBS 未名空间站 (Tue Dec 27 23:05:01 2011, 美东)
一个同事刚刚推荐的。网上搜索了一下,好像是个LIFE INSURANCE之类的东东。有个保
底的回报率(1-3%)。如果股票市场INDEX是9%的回报率,它可以给你7.2%。但是加入
是负数,它也给你1-3%.对于我这种已经要考虑退休的人来说还是很有吸引了的。但是
我对金融投资一窍不通,不知道值不值得。谢谢。
附网上找到的几个:
http://www.avivausa.com/portal/site/avivausa/content/home/annui
http://www.retirement-income.net/blog/fixedannuities/tax-deferr
http://www.freeannuityrates.com/annuities/index/index-annuity-... 阅读全帖
t**********2
发帖数: 6
27
来自主题: Stock版 - 菜鸟问个初级问题about INDEX
根据我的理解你可以通过史考特买index ETF 这个ETF和股票一样 但是你要给史考特 费
用。 也可以通过基金公司 比如vanguard 买ETF(省去comission fee)
也可以买index mutual fund 不收comission fee 但是收management fee 比如 0.17%
vfinx (<$10k)0.05% vfiax
ETF 价格随时变动
mutual fund 一天一个价

号,可以直接用这个账号像买一般的stock一样买index吗?另外有什么好的index推荐吗
t**o
发帖数: 6659
28
Not a good way to buy.
Index is higher by 10%, my stock index etf only by 5%. But index lower by 10
%, my stock index ETF down by more than 10%.
FK, I hate it. After holding for 4 years, I cut my loss at 15%
K**e
发帖数: 56
29
Some quotes from CBOE website: http://www.cboe.com/products/indexopts/vixoptions_spec.aspx
Exercise Style: European - CBOE Volatility Index options generally may be
exercised only on the Expiration Date.
Settlement of Option Exercise: Exercise will result in delivery of cash on
the business day following expiration. The exercise-settlement amount is
equal to the difference between the exercise-settlement value and the
exercise price of the option, multiplied by $100.
If more people think the vo... 阅读全帖
h*******n
发帖数: 1328
30
来自主题: Immigration版 - 有人用H-index吹杂志排名吗?
你先用中文给我们解释一下H-index 怎么吹杂志?
用H-index吹你自己可以
吹杂志怎么个吹发,我还真想不出来
本来这个index就是评价作者的一个指标不是评价文章的指标
你说再XXX杂志上发表文章的人H-index都没你高?
这个是说这个杂志好还是差?
解释一个,开开思路
h*******n
发帖数: 1328
31
来自主题: Immigration版 - 有人用H-index吹杂志排名吗?
你先用中文给我们解释一下H-index 怎么吹杂志?
用H-index吹你自己可以
吹杂志怎么个吹发,我还真想不出来
本来这个index就是评价作者的一个指标不是评价文章的指标
你说再XXX杂志上发表文章的人H-index都没你高?
这个是说这个杂志好还是差?
解释一个,开开思路
q*********a
发帖数: 178
32
来自主题: Immigration版 - 用h-index比较top small percentage
为什么没看到有人用过?
h-index作者Hirsh说Physics的如果有h-index=12就可以拿tenure了
Microsoft Academic Search可以用h-index rank一个领域,这样就有small
percentage了,跟那些大牛直接比,很有说服力
还没试过g-index...
l*******w
发帖数: 312
33
来自主题: Immigration版 - google scholar h-index 什么意识?
h-index 2 2
i10-index 0 0
我查了一下google scholar, h-index =2, i10-index =0
什么意思?
r***n
发帖数: 579
34
以下内容仅供参考,我的背景请见http://www.mitbbs.com/article_t/Immigration/33352953.html
如有疑问,请跟贴或站内信箱联系。祝战友绿卡之路顺利!
Index of Exhibits
Exhibit A. Evidence of the alien’s participation, either individually or on
a panel, as a judge of the work of others in the same or an allied field of
specialization for which classification is sought.
A1: A copy of the web page of the American Journal of xxxx showing xxxx as a
reviewer………………………………………………………...1
A2: A copy of the web page of the American Journal of xxxx showing x... 阅读全帖
r***n
发帖数: 579
35
以下内容仅供参考,我的背景请见http://www.mitbbs.com/article_t/Immigration/33352953.html
如有疑问,请跟贴或站内信箱联系。祝战友绿卡之路顺利!
Index of Exhibits
Exhibit A. Evidence of the alien’s participation, either individually or on
a panel, as a judge of the work of others in the same or an allied field of
specialization for which classification is sought.
A1: A copy of the web page of the American Journal of xxxx showing xxxx as a
reviewer………………………………………………………...1
A2: A copy of the web page of the American Journal of xxxx showing x... 阅读全帖
g******4
发帖数: 6339
36
来自主题: Chicago版 - House price index
[3] CoreLogic HPI
The CoreLogic Home Price Index, introduced in 2008, is a repeat-sales index
that tracks increases and decreases in sales prices for the same homes over
time, including single-family attached and single-family detached homes. The
CoreLogic HPI provides a multi-tier market evaluation of repeat sales
transactions based on price, time between sales, property type, loan type (
conforming vs. nonconforming) and distressed sales. Released once a month,
the CoreLogic HPI has a lag time... 阅读全帖
g******4
发帖数: 6339
37
来自主题: Chicago版 - House price index
[4] IAS360
The IAS360 House Price Index provides a monthly view of housing price trends
in the U.S. based on neighborhood level data (market trends at a county
level). IAS360 is a comprehensive housing index tracking monthly change in
the median sales price of detached single-family residences in more than 15,
000 “neighborhoods” across the country. This data is then rolled up to
report on the changes in 360 counties, nine census divisions, four regions,
and the nation overall. This index is rel... 阅读全帖
g******4
发帖数: 6339
38
来自主题: Chicago版 - House price index
[3] CoreLogic HPI
The CoreLogic Home Price Index, introduced in 2008, is a repeat-sales index
that tracks increases and decreases in sales prices for the same homes over
time, including single-family attached and single-family detached homes. The
CoreLogic HPI provides a multi-tier market evaluation of repeat sales
transactions based on price, time between sales, property type, loan type (
conforming vs. nonconforming) and distressed sales. Released once a month,
the CoreLogic HPI has a lag time... 阅读全帖
g******4
发帖数: 6339
39
来自主题: Chicago版 - House price index
[4] IAS360
The IAS360 House Price Index provides a monthly view of housing price trends
in the U.S. based on neighborhood level data (market trends at a county
level). IAS360 is a comprehensive housing index tracking monthly change in
the median sales price of detached single-family residences in more than 15,
000 “neighborhoods” across the country. This data is then rolled up to
report on the changes in 360 counties, nine census divisions, four regions,
and the nation overall. This index is rel... 阅读全帖
n*e
发帖数: 34
40
来自主题: Seattle版 - 一个有意思的概念:Kolbe Index
这几天看Rich Dad's Guide to Investing,其中有个Kolbe Index第一次听说。没钱真
的去做网上测试,不过以我的理解主要是说人各有天生的能力(Kolbe Index讲
instinct),Kolbe Index把这些能力分了四类。
Fact finder: 查detailed information;
Follow through: 是解决表面问题,还是建个系统一劳永逸地解决问题;
Quick start: 创新能力;
Implementor: hands-on building and fixing.
每个人根据所长会有个表,象
Fact finder | Follow Thru | Quick Start | Implementor
Prevent problems
|
V
Respond
|
V
Initiate Solutions
光看这些,觉得和MBT... 阅读全帖
c*****t
发帖数: 1879
41
Index is automatically used by the query engine while explicitly
specifying sorting is done by the user who does the query.
Usually, when index is used, tuples are retrieved in the order
they appear in the index, so they are sort in a way, although
may not be in the order wanted by the user.
When user explicitly specify the query order, if there is no
such index for the column, in memory sorting is performed before
result is returned.

an
t***s
发帖数: 48
42
我需要index大概四百万个ascii文件。哪位高人给推荐个好用的text indexer。多谢。
简单的说,就是个类似于text search engine里面indexer那一部分,但是提供比较方
便的command line access。最好在windows上。
具体点,就是能够index这四百万文件,把结果放在一个可以从command line方便读取
的repository里。可以是relational database或者其他proprietary的格式,只要能够
从command line或者perl之类的scripts读,结果能输出到ascii文件就可以。当然如果
可以从数据库里直接用SQL读更好。
安装越简单越好。最好都是command line。
我试过微软的search server和open source的lucene,都不太满意,主要是输出都是
web pages。像我的情况一个关键字上百页的输出。处理起来太麻烦。
再谢。
b******A
发帖数: 4967
43
请问一下各位大神,有木有办法可以通过一次indexing两个HBase table
目前我的morphline-hbase-mapper.xml长这个样子,这个需要怎么改额,任何建议都非
常感谢!
$ vim morphline-hbase-mapper.xml




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s**o
发帖数: 584
44
来自主题: Database版 - 问一个Oralce index的问题
you are right on that. 'A%' is a little bit special, you will get a index
range scan. The statement give him an index full scan due to "Select last_
name from ...". It will give a index range scan if the upper() function
index is built or the upper() clause is removed.
w*******e
发帖数: 1622
45
来自主题: Database版 - indexing就是设置primary key吗?
准确的说是: 如果没clustered Index, 那么it will automatically create a
clustered index on the PK for you.
如果有个clustered index 存在了, 那就是automatically create a non-clustered
index on that PK for you.
a*******s
发帖数: 324
46
来自主题: Database版 - 如何决定index
table1 10k
id not index or index
table2 100m
id not indexed
where table1.id = table2.id
They are almost the same. Database is postgre. Not sure if postgre will
index the table1.id in the memory.
u******u
发帖数: 595
47
来自主题: Database版 - 如何决定index
There is NO fixed standard to use index or not.
As the data keep changing, you may find your old query becomes slow. Adding
a index will help your query in most cases.
However, too many indexed columns will NOT help your DML (inert/update/
delete).
Need watch the performance to see whether the index is helpful or not.
Thanks!
美国老土
n********6
发帖数: 1511
48
来自主题: Database版 - 请教 sql server index问题
一个table,用于存放business order,25+ column。 8+ index。有几个column是日期
。其中1个日期上有non-clustered index。table有10-50millions of records。在
production environment24*7。
问题:
1。在何种条件下在日期上建议用index?
2。过多的index导致performance下降。如何衡量过多?
l******r
发帖数: 99
49
来自主题: Database版 - Oracle Group and Index question
I have a table A, which has 50 millions records.
In this table A, I have two columns id and date.
if I run the following query:
select date, sum(id) from A group by date
it will take 10 minutes to finish.
what can I do to improve the performance?
there are 3 bitmap indexes for this table A.
index 1 is on column id.
index 2 is on column date.
index 3 is on column id and column date.
Please help. Thanks.
s******g
发帖数: 287
50
来自主题: Database版 - 问个Index的问题
比如说设计一个银行的数据库,
有一个table叫transaction(transactionID, accountID, date, ...)
-------------
这个表显然经常需要更新,主要是一条一条的insert操作
这样看来,为了performance,尽量减少index,那么不应该在accountID上建index
不然,每次insert都需要更新这个index(?)
然而,用户(和银行)也需要查询某账户近期的所有transactions
这样似乎又需要给accountID建一个index
想请教一下实际设计中是怎么做的?谢谢!
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