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Fix division by zero in phrase suggester that causes assertion to fail #27149

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Oct 30, 2017
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Fix division by zero in phrase suggester that causes assertion to fail #27149

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5 changes: 4 additions & 1 deletion core/src/main/java/org/elasticsearch/search/suggest/phrase/WordScorer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -57,7 +57,10 @@ public WordScorer(IndexReader reader, Terms terms, String field, double realWord
final long vocSize = terms.getSumTotalTermFreq();
this.vocabluarySize = vocSize == -1 ? reader.maxDoc() : vocSize;
this.useTotalTermFreq = vocSize != -1;
this.numTerms = terms.size();
long numTerms = terms.size();
// -1 cannot be used as value, because scoreUnigram(...) can then divide by 0 if vocabluarySize is 1.
// -1 is returned when terms is a MultiTerms instance.
this.numTerms = vocabluarySize + numTerms > 1 ? numTerms : 0;
this.termsEnum = new FreqTermsEnum(reader, field, !useTotalTermFreq, useTotalTermFreq, null, BigArrays.NON_RECYCLING_INSTANCE); // non recycling for now
this.reader = reader;
this.realWordLikelyhood = realWordLikelyHood;
Expand Down
30 changes: 27 additions & 3 deletions .../src/test/java/org/elasticsearch/search/suggest/phrase/NoisyChannelSpellCheckerTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@
import org.apache.lucene.analysis.miscellaneous.PerFieldAnalyzerWrapper;
import org.apache.lucene.analysis.reverse.ReverseStringFilter;
import org.apache.lucene.analysis.shingle.ShingleFilter;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.analysis.standard.StandardTokenizer;
import org.apache.lucene.analysis.synonym.SolrSynonymParser;
import org.apache.lucene.analysis.synonym.SynonymFilter;
Expand All @@ -38,16 +39,14 @@
import org.apache.lucene.index.MultiFields;
import org.apache.lucene.search.spell.DirectSpellChecker;
import org.apache.lucene.search.spell.SuggestMode;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.RAMDirectory;
import org.apache.lucene.util.BytesRef;
import org.elasticsearch.search.suggest.phrase.NoisyChannelSpellChecker.Result;
import org.elasticsearch.test.ESTestCase;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;

Expand Down Expand Up @@ -439,4 +438,29 @@ protected TokenStreamComponents createComponents(String fieldName) {
assertThat(corrections[0].join(new BytesRef(" ")).utf8ToString(), equalTo("xorr the god jewel"));
assertThat(corrections[1].join(new BytesRef(" ")).utf8ToString(), equalTo("xor the god jewel"));
}

public void testFewDocsEgdeCase() throws Exception {
try (Directory dir = newDirectory()) {
try (IndexWriter iw = new IndexWriter(dir, newIndexWriterConfig())) {
Document document = new Document();
document.add(new TextField("field", "value", Field.Store.NO));
iw.addDocument(document);
iw.commit();
document = new Document();
document.add(new TextField("other_field", "value", Field.Store.NO));
iw.addDocument(document);
}

try (DirectoryReader ir = DirectoryReader.open(dir)) {
WordScorer wordScorer = new StupidBackoffScorer(ir, MultiFields.getTerms(ir, "field"), "field", 0.95d, new BytesRef(" "), 0.4f);
NoisyChannelSpellChecker suggester = new NoisyChannelSpellChecker();
DirectSpellChecker spellchecker = new DirectSpellChecker();
DirectCandidateGenerator generator = new DirectCandidateGenerator(spellchecker, "field", SuggestMode.SUGGEST_MORE_POPULAR, ir, 0.95, 5);
Result result = suggester.getCorrections(new StandardAnalyzer(), new BytesRef("valeu"), generator, 1, 1, ir, "field", wordScorer, 1, 2);
assertThat(result.corrections.length, equalTo(1));
assertThat(result.corrections[0].join(space).utf8ToString(), equalTo("value"));
}
}
}

}