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From Ian Lea <ian....@gmail.com>
Subject Re: Shingles Filter problems
Date Tue, 11 Oct 2011 19:51:27 GMT
Something does appear dodgy here.  Using 3.4.0 the following very
simple code, with no custom classes

	ShingleAnalyzerWrapper saw = new ShingleAnalyzerWrapper(LUCENE_34);
	QueryParser qp = new QueryParser(LUCENE_34, "t", saw);
	String s = "simple sentences rule";
	Query q = qp.parse(s);
	System.out.printf("%s parsed to %s\n", s, q);

produces

simple sentences rule parsed to t:simple t:sentences t:rule

Like you, I would have expected there to be some shingles in there.
Are we both missing something?


--
Ian.


On Tue, Oct 11, 2011 at 3:25 PM, Peyman Faratin <peyman@robustlinks.com> wrote:
> Hi
>
> I have the following shinglefilter (Lucene 3.2)
>
>          public TokenStream tokenStream(String fieldName, Reader reader) {
>                  StandardTokenizer first = new StandardTokenizer(Version.LUCENE_32,
reader);
>                  StandardFilter second = new StandardFilter(Version.LUCENE_32,first);
>                  LowerCaseFilter third = new LowerCaseFilter(Version.LUCENE_32,second);
>                  StopFilter fourth = new StopFilter(Version.LUCENE_32,third,Stopwords);
>                  PositionFilter fifth = new PositionFilter(fourth);
>                  ShingleFilter filter = new ShingleFilter(fifth,shingleSize);
>                   return filter;
>                }
>
> that produces the following token stream given sentence
>
> "please parse this sentence into a shingle of size 2. I'll pay $2 for it"
>
> 1: [_ parse:7->12:shingle]
> 2: [parse:7->12:<ALPHANUM>] [parse sentence:7->26:shingle]
> 3: [sentence:18->26:<ALPHANUM>] [sentence shingle:18->41:shingle]
> 4: [shingle:34->41:<ALPHANUM>] [shingle size:34->49:shingle]
> 5: [size:45->49:<ALPHANUM>] [size 2:45->51:shingle]
> 6: [2:50->51:<NUM>] [2 pay:50->61:shingle]
> 7: [pay:58->61:<ALPHANUM>] [pay 2:58->64:shingle]
> 8: [2:63->64:<NUM>]
>
> The query analyzer produces the following analyzed query for the field "titleShingled"
for above sentence:
>
> ...... analyzed query:titleShingled:parse titleShingled:sentence titleShingled:shingle
titleShingled:size titleShingled:2 titleShingled:pay titleShingled:2
>
> As you can see there is no bigram singles in the query. I tried removing the unigrams
from the token stream (using  filter.setOutputUnigrams(false) in above shingles filter) but
even though the singles seem to be fine the query is empty
>
>
> 1: [_ parse:7->12:shingle]
> 2: [parse sentence:7->26:shingle]
> 3: [sentence shingle:18->41:shingle]
> 4: [shingle size:34->49:shingle]
> 5: [size 2:45->51:shingle]
> 6: [2 pay:50->61:shingle]
> 7: [pay 2:58->64:shingle]
>
> ...... analyzed query:
>
> My goal is to index both unigrams and bigrams but first try to search on bigrams. I think
it is the queryparser that is parsing the shingles in a manner that I am not understanding
properly.
>
>                  QueryParser parser = new QueryParser(Version.LUCENE_32,"titleShingled",new
ShinglesAnalyzer(2,Stopwords));
>
> Any help would be very much appreciated
>
> Peyman
>
>

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