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From Arjen van der Meijden <>
Subject Re: How to handle words that stem to stop words
Date Thu, 10 Jul 2014 21:07:44 GMT
Hi Sujit,

Thanks. I was thinking along those lines myself. And reversely, the same 
list of stopwords could be used to mark the stopwords as keyword as 
well, to prevent them from collapsing with rare words.

Best regards,


On 10-7-2014 22:30 Sujit Pal wrote:
> Hi Arjen,
> This is kind of a spin on your last observation that your list of stop
> words don't change frequently. If you have a custom filter that attempts to
> stem the incoming token and if it stems to the same as a stopword, only
> then sets the keyword attribute on the original token.
> That way your reindex frequency is based on the stopword change frequency
> not on the frequency of discovery of new words that stem to stopwords.
> -sujit
> On Thu, Jul 10, 2014 at 11:57 AM, Arjen van der Meijden <
>> wrote:
>> I'm reluctant to apply either solution:
>> Emitting both tokens will likely still provide the user with a very long
>> result list. Even though the results with 'vans' in it are likely to be
>> ranked to the top, its still not very user friendly due to its
>> overwhelmingly large number of results (nor is it very good for the
>> performance of my application).
>> In our specific case we also boost documents based on their age and
>> popularity, so the extra results will probably interfere even if
>> 'vans'-results are generally ranked higher.
>> The approach with a list of specially treated terms is something we'll
>> have to build and maintain by hand. Every time such a list is adjusted,
>> it'll require a reindex of the database, which is not a huge problem but
>> still not very practical.
>> But I'm getting more and more convinced there isn't really a (reasonably
>> easy) solution that would leave it dynamically changing without requiring
>> database reindexes.
>> Luckily the list of stop words shouldn't change that fast and we already
>> have more than ten years worth of data, so it should be fairly easy to
>> build a list of terms that are stemmed into stop words.
>> Best regards,
>> Arjen
>> On 7-7-2014 23:06 Tri Cao wrote:
>>> I think emitting two tokens for "vans" is the right (potentially only)
>>> way to do it. You could
>>> also control the dictionary of terms that require this special treatment.
>>> Any reason makes you not happy with this approach?
>>> On Jul 06, 2014, at 11:48 AM, Arjen van der Meijden
>>> <> wrote:
>>>   Hello list,
>>>> We have a fairly large Lucene database for a 30+ million post forum.
>>>> Users post and search for all kinds of things. To make sure users don't
>>>> have to type exact matches, we combine a WordDelimiterFilter with a
>>>> (Dutch) SnowballFilter.
>>>> Unfortunately users sometimes find examples of words that get stemmed to
>>>> a word that's basically a stop word. Or reversely, where a very common
>>>> word is stemmed so that it becomes the same as a rare word.
>>>> We do index stop words, so theoretically they could still find their
>>>> result. But when a rare word is stemmed in such a way it yields a
>>>> million hits, that makes it very unusable...
>>>> One example is the Dutch word 'van' which is the equivalent of 'of' in
>>>> English. A user tried to search for the shoe brand 'vans', which gets
>>>> stemmed to 'van' and obviously gives useless results.
>>>> I already noticed the 'KeywordRepeatFilter' to index/search both 'vans'
>>>> and 'van' and the StemmerOverrideFilter to try and prevent these cases.
>>>> Are there any other solutions for these kinds of problems?
>>>> Best regards,
>>>> Arjen van der Meijden
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