答复: [SPAM] Re: A Problem in Customizing DefaultSimilarity

["Oliver Xu (Aigine Co)" <ol...@aigine.com>]

Lovely. Thank you very much! Oliver

-----邮件原件-----
发件人: java-user-return-56101-oliver.xu=aigine.com@lucene.apache.org
[mailto:java-user-return-56101-oliver.xu=aigine.com@lucene.apache.org] 代表
Koji Sekiguchi
发送时间: 2013年6月12日 22:47
收件人: java-user@lucene.apache.org
主题: [SPAM] Re: A Problem in Customizing DefaultSimilarity

Hi Oliver,

> My questions are:
> 
> 1.       Why are the overrided lengthNorm() (under Lucene410) or
> computeNorm() (under Lucene350) methods not called during a searching
> process?

Regardless of whether you override the method or not, Lucene framework
calls the method during index time only because length norm can be
calculated by using the number of tokens in the field, i.e. not need to call
it search time.

> 2.       How and where is fieldNorm calculated?

I think fieldNorm = lengthNorm * boost of the field. Please see Javadoc for
more detail:

http://lucene.apache.org/core/4_3_0/core/org/apache/lucene/search/similariti
es/TFIDFSimilarity.html

koji
-- 
http://soleami.com/blog/automatically-acquiring-synonym-knowledge-from-wikip
edia.html

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Re: 答复: [SPAM] Re: A Problem in Customizing DefaultSimilarity

[Varun Thacker <va...@gmail.com>]

Hi Oliver,
I would like to add a couple of things here..

1. Regarding lengthNorm being called you will also have to make sure that
you set your custom similarity class during index by calling
IndexWriterConfig.setSimilarity(new CustomSimilarity());


2. From what I can see in the source for computeNorm basically calls
fieldNorm and encodes it so that it can be stored in the index


On Thu, Jun 13, 2013 at 6:24 AM, Oliver Xu (Aigine Co) <oliver.xu@aigine.com
> wrote:

> Lovely. Thank you very much! Oliver
>
> -----邮件原件-----
> 发件人: java-user-return-56101-oliver.xu=aigine.com@lucene.apache.org
> [mailto:java-user-return-56101-oliver.xu=aigine.com@lucene.apache.org] 代表
> Koji Sekiguchi
> 发送时间: 2013年6月12日 22:47
> 收件人: java-user@lucene.apache.org
> 主题: [SPAM] Re: A Problem in Customizing DefaultSimilarity
>
> Hi Oliver,
>
> > My questions are:
> >
> > 1.       Why are the overrided lengthNorm() (under Lucene410) or
> > computeNorm() (under Lucene350) methods not called during a searching
> > process?
>
> Regardless of whether you override the method or not, Lucene framework
> calls the method during index time only because length norm can be
> calculated by using the number of tokens in the field, i.e. not need to
> call
> it search time.
>
> > 2.       How and where is fieldNorm calculated?
>
> I think fieldNorm = lengthNorm * boost of the field. Please see Javadoc for
> more detail:
>
>
> http://lucene.apache.org/core/4_3_0/core/org/apache/lucene/search/similariti
> es/TFIDFSimilarity.html
>
> koji
> --
>
> http://soleami.com/blog/automatically-acquiring-synonym-knowledge-from-wikip
> edia.html
>
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>


-- 


Regards,
Varun Thacker
http://www.vthacker.in/