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https://issues.apache.org/jira/browse/LUCENE-5396?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15464535#comment-15464535
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Christoph Goller commented on LUCENE-5396:
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Is this a bug or desired bahavior?
For me it is at least an acceptable behavior. I like the behavior of unordered
SpanNearQuery to match if clauses overlap or match at the same position. and it
would be quite difficult to find out if two clauses match at the same index
term or only at the same position.
background: I am using a component for word decomposition. This might be a very
rare case for English but it is a much more common phenomen for German and
Dutch. The two compound parts of "wallpaper" (wall and paper) go into the same
index position as wallpaper. I am using spanNear([wall, paper], 0, false) to
search for wallpaper and expect matches for "wallpaper" as well as for "wall
paper".
So far we do not have a proper definition of what SpanQueries should do and the
only way to find out what they currently do is to look into the code. I think
the current behavior is not very consistent. I will present some of my
insights and ideas in LUCENE-7398.
> SpanNearQuery returns single term spans
> ---------------------------------------
>
> Key: LUCENE-5396
> URL: https://issues.apache.org/jira/browse/LUCENE-5396
> Project: Lucene - Core
> Issue Type: Bug
> Components: core/search
> Reporter: Piotr Pęzik
>
> Let's assume we have an index with two documents:
> 1. contents: "test bunga bunga test"
> 2. contents: "test bunga test"
> We run two SpanNearQueries against this index:
> 1. spanNear([contents:bunga, contents:bunga], 0, true)
> 2. spanNear([contents:bunga, contents:bunga], 0, false)
> For the first query we get 1 hit. The first document in the example above
> gets matched and the second one doesn't. This make sense, because we want the
> term "bunga" followed by another "bunga" here.
> However, both documents get matched by the second query. This is also
> problematic in cases where we have duplicate terms in longer (unordered)
> spannear queries, e. g.: unordered 'A B A' will match spans such as 'A B' or
> 'B A'.
> A complete example follows.
> ---------
> import org.apache.lucene.analysis.Analyzer;
> import org.apache.lucene.analysis.standard.StandardAnalyzer;
> import org.apache.lucene.document.Document;
> import org.apache.lucene.document.TextField;
> import org.apache.lucene.index.DirectoryReader;
> import org.apache.lucene.index.IndexWriter;
> import org.apache.lucene.index.IndexWriterConfig;
> import org.apache.lucene.index.Term;
> import org.apache.lucene.search.IndexSearcher;
> import org.apache.lucene.search.TopDocs;
> import org.apache.lucene.search.spans.SpanNearQuery;
> import org.apache.lucene.search.spans.SpanQuery;
> import org.apache.lucene.search.spans.SpanTermQuery;
> import org.apache.lucene.store.Directory;
> import org.apache.lucene.store.FSDirectory;
> import org.apache.lucene.store.RAMDirectory;
> import org.apache.lucene.util.Version;
> import java.io.StringReader;
> import static org.junit.Assert.assertEquals;
> class SpansBug {
> public static void main(String [] args) throws Exception {
> Directory dir = new RAMDirectory();
> Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_45);
> IndexWriterConfig iwc = new IndexWriterConfig(Version.LUCENE_45,
> analyzer);
> IndexWriter writer = new IndexWriter(dir, iwc);
> String contents = "contents";
> Document doc1 = new Document();
> doc1.add(new TextField(contents, new StringReader("test bunga bunga
> test")));
> Document doc2 = new Document();
> doc2.add(new TextField(contents, new StringReader("test bunga
> test")));
> writer.addDocument(doc1);
> writer.addDocument(doc2);
> writer.commit();
> IndexSearcher searcher = new IndexSearcher(DirectoryReader.open(dir));
> SpanQuery stq1 = new SpanTermQuery(new Term(contents,"bunga"));
> SpanQuery stq2 = new SpanTermQuery(new Term(contents,"bunga"));
> SpanQuery [] spqa = new SpanQuery[]{stq1,stq2};
> SpanNearQuery spanQ1 = new SpanNearQuery(spqa,0, true);
> SpanNearQuery spanQ2 = new SpanNearQuery(spqa,0, false);
> System.out.println(spanQ1);
> TopDocs tdocs1 = searcher.search(spanQ1,10);
> assertEquals(tdocs1.totalHits ,1);
> System.out.println(spanQ2);
> TopDocs tdocs2 = searcher.search(spanQ2,10);
> //I'd expect one hit here:
> assertEquals(tdocs2.totalHits ,1); // Assertion fails
> }
> }
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