Hi Eva,
This looks like a bug in WeightedSpanTermExtractor, which is rewriting your
PhraseQuery into a SpanNearQuery without checking how many terms there are.
Could you open a JIRA ticket?
Alan Woodward
www.flax.co.uk
> On 18 Apr 2016, at 16:27, Eva Popenda <eva.pope...@abas.de> wrote:
>
> Hi,
>
> I have a problem when using the Highlighter with N-GramAnalyzer and
> PhraseQuery:
> Searching for a substring with length = N (4 in my case) yields the following
> exception:
>
> java.lang.IllegalArgumentException: Less than 2 subSpans.size():1
> at
> org.apache.lucene.search.spans.ConjunctionSpans.<init>(ConjunctionSpans.java:40)
> at
> org.apache.lucene.search.spans.NearSpansOrdered.<init>(NearSpansOrdered.java:56)
> at
> org.apache.lucene.search.spans.SpanNearQuery$SpanNearWeight.getSpans(SpanNearQuery.java:232)
> at
> org.apache.lucene.search.highlight.WeightedSpanTermExtractor.extractWeightedSpanTerms(WeightedSpanTermExtractor.java:292)
> at
> org.apache.lucene.search.highlight.WeightedSpanTermExtractor.extract(WeightedSpanTermExtractor.java:137)
> at
> org.apache.lucene.search.highlight.WeightedSpanTermExtractor.getWeightedSpanTerms(WeightedSpanTermExtractor.java:506)
> at
> org.apache.lucene.search.highlight.QueryScorer.initExtractor(QueryScorer.java:219)
> at org.apache.lucene.search.highlight.QueryScorer.init(QueryScorer.java:187)
> at
> org.apache.lucene.search.highlight.Highlighter.getBestTextFragments(Highlighter.java:196)
>
> Below is a JUnit-Test reproducing this behavior. In case of searching for a
> string with more than N characters or using NGramPhraseQuery this problem
> doesn't occur.
> Why is it that more than 1 subSpans are required?
>
> public class HighlighterTest {
>
> @Rule
> public final ExpectedException exception = ExpectedException.none();
>
> @Test
> public void testHighlighterWithPhraseQueryThrowsException() throws
> IOException, InvalidTokenOffsetsException {
>
> final Analyzer analyzer = new NGramAnalyzer(4);
> final String fieldName = "substring";
>
> final List<BytesRef> list = new ArrayList<>();
> list.add(new BytesRef("uchu"));
> final PhraseQuery query = new PhraseQuery(fieldName, list.toArray(new
> BytesRef[list.size()]));
>
> final QueryScorer fragmentScorer = new QueryScorer(query, fieldName);
> final SimpleHTMLFormatter formatter = new SimpleHTMLFormatter("<b>",
> "</b>");
>
> exception.expect(IllegalArgumentException.class);
> exception.expectMessage("Less than 2 subSpans.size():1");
>
> final Highlighter highlighter = new
> Highlighter(formatter,TextEncoder.NONE.getEncoder(), fragmentScorer);
> highlighter.setTextFragmenter(new SimpleFragmenter(100));
> final String fragment = highlighter.getBestFragment(analyzer,
> fieldName, "Buchung");
>
> assertEquals("B<b>uchu</b>ng",fragment);
>
> }
>
> public final class NGramAnalyzer extends Analyzer {
>
> private final int minNGram;
>
> public NGramAnalyzer(final int minNGram) {
> super();
> this.minNGram = minNGram;
> }
>
> @Override
> protected TokenStreamComponents createComponents(final String fieldName) {
> final Tokenizer source = new NGramTokenizer(minNGram, minNGram);
> return new TokenStreamComponents(source);
> }
>
> }
>
> }
>
> Thanks and cheers,
> Eva
>
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