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From "Binkley, Peter" <>
Subject RE: multi-language searching with Solr
Date Mon, 05 May 2008 21:38:39 GMT
It won't make much difference to the index size, since you'll only be
populating one of the language fields for each document, and empty
fields cost nothing. The performance may suffer a bit but Lucene may
surprise you with how good it is with that kind of boolean query. 

I agree that as the number of fields and languages increases, this is
going to become a lot to manage. But you're up against some basic
problems when you try to model this in Solr: for each token, you care
about not just its value (which is all Lucene cares about) but also its
language and its stem; and the stem for a given token depends on the
language (different stemming rules); and at query time you may not know
the language. I don't think you're going to get a solution without some
redundancy; but solving problems by adding redundant fields is a common
method in Solr.


-----Original Message-----
From: Eli K [] 
Sent: Monday, May 05, 2008 2:28 PM
Subject: Re: multi-language searching with Solr

Wouldn't this impact both indexing and search performance and the size
of the index?
It is also probable that I will have more then one free text fields
later on and with at least 20 languages this approach does not seem very
manageable.  Are there other options for making this work with stemming?



On Mon, May 5, 2008 at 3:41 PM, Binkley, Peter
<> wrote:
> I think you would have to declare a separate field for each language  
> (freetext_en, freetext_fr, etc.), each with its own appropriate  
> stemming. Your ingestion process would have to assign the free text  
> content for each document to the appropriate field; so, for each  
> document, only one of the freetext fields would be populated. At 
> search  time, you would either search against the appropriate field if

> you know  the search language, or search across them with 
> "freetext_fr:query OR  freetext_en:query OR ...". That way your query 
> will be interpreted by  each language field using that language's
stemming rules.
>  Other options for combining indexes, such as copyfield or dynamic 
> fields  (see, would lead to a 
> single  field type and therefore a single type of stemming. You could 
> always use  copyfield to create an unstemmed common index, if you 
> don't care about  stemming when you search across languages (since 
> you're likely to get  odd results when a query in one language is 
> stemmed according to the  rules of another language).
>  Peter
>  -----Original Message-----
>  From: Eli K []
>  Sent: Monday, May 05, 2008 8:27 AM
>  To:
>  Subject: multi-language searching with Solr
>  Hello folks,
>  Let me start by saying that I am new to Lucene and Solr.
>  I am in the process of designing a search back-end for a system that

> receives 20k documents a day and needs to keep them available for 30  
> days.  The documents should be searchable on a free text field and on

> about 8 other fields.
>  One of my requirements is to index and search documents in multiple  
> languages.  I would like to have the ability to stem and provide the  
> advanced search features that are based on it.  This will only affect

> the free text field because the rest of the fields are in English.
>  I can find out the language of the document before indexing and I 
> might  be able to provide the language to search on.  I also need to 
> have the  ability to search across all indexed languages (there will 
> be 20 in  total).
>  Given these requirements do you think this is doable with Solr?  A 
> major  limiting factor is that I need to stick to the 1.2 GA version 
> and I  cannot utilize the multi-core features in the 1.3 trunk.
>  I considered writing my own analyzer that will call the appropriate  
> Lucene analyzer for the given language but I did not see any way for 
> it  to access the field that specifies the language of the document.
>  Thanks,
>  Eli
>  p.s. I am looking for an experienced Lucene/Solr consultant to help 
> with  the design of this system.

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