Added specific rescore exception, refactor code

Signed-off-by: Martin Gaievski <[email protected]>

src/main/java/org/opensearch/neuralsearch/search/query/HybridCollectorManager.java

@@ -19,7 +19,6 @@
 import org.apache.lucene.search.SortField;
 import org.apache.lucene.search.TopFieldDocs;
 import org.apache.lucene.search.FieldDoc;
-import org.opensearch.OpenSearchException;
 import org.opensearch.common.Nullable;
 import org.opensearch.common.lucene.search.FilteredCollector;
 import org.opensearch.common.lucene.search.TopDocsAndMaxScore;
@@ -37,6 +36,7 @@
 import org.opensearch.search.query.ReduceableSearchResult;
 import org.opensearch.search.rescore.RescoreContext;
 import org.opensearch.search.sort.SortAndFormats;
+import org.opensearch.neuralsearch.search.query.exception.HybridSearchRescoreQueryException;
 
 import java.io.IOException;
 import java.util.ArrayList;
@@ -189,23 +189,22 @@ private TopDocsAndMaxScore getSortedTopDocsAndMaxScore(List<TopFieldDocs> topDoc
     }
 
     private TopDocsAndMaxScore getTopDocsAndMaxScore(List<TopDocs> topDocs, HybridSearchCollector hybridSearchCollector) {
-        List<TopDocs> rescoredTopDocs = rescore(topDocs);
-        float maxScore = calculateMaxScore(rescoredTopDocs, hybridSearchCollector.getMaxScore());
-        TopDocs finalTopDocs = getNewTopDocs(
-            getTotalHits(this.trackTotalHitsUpTo, rescoredTopDocs, hybridSearchCollector.getTotalHits()),
-            rescoredTopDocs
-        );
+        if (shouldRescore()) {
+            topDocs = rescore(topDocs);
+        }
+        float maxScore = calculateMaxScore(topDocs, hybridSearchCollector.getMaxScore());
+        TopDocs finalTopDocs = getNewTopDocs(getTotalHits(this.trackTotalHitsUpTo, topDocs, hybridSearchCollector.getTotalHits()), topDocs);
         return new TopDocsAndMaxScore(finalTopDocs, maxScore);
     }
 
-    private List<TopDocs> rescore(List<TopDocs> topDocs) {
+    private boolean shouldRescore() {
         List<RescoreContext> rescoreContexts = searchContext.rescore();
-        boolean shouldRescore = Objects.nonNull(rescoreContexts) && !rescoreContexts.isEmpty();
-        if (!shouldRescore) {
-            return topDocs;
-        }
+        return Objects.nonNull(rescoreContexts) && !rescoreContexts.isEmpty();
+    }
+
+    private List<TopDocs> rescore(List<TopDocs> topDocs) {
         List<TopDocs> rescoredTopDocs = topDocs;
-        for (RescoreContext ctx : rescoreContexts) {
+        for (RescoreContext ctx : searchContext.rescore()) {
             rescoredTopDocs = rescoredTopDocs(ctx, rescoredTopDocs);
         }
         return rescoredTopDocs;
@@ -220,8 +219,8 @@ private List<TopDocs> rescoredTopDocs(final RescoreContext ctx, final List<TopDo
             try {
                 result.add(ctx.rescorer().rescore(topDoc, searchContext.searcher(), ctx));
             } catch (IOException exception) {
-                log.error("rescore failed for hybrid query", exception);
-                throw new OpenSearchException("rescore failed", exception);
+                log.error("rescore failed for hybrid query in collector_manager.reduce call", exception);
+                throw new HybridSearchRescoreQueryException(exception);
             }
         }
         return result;

src/main/java/org/opensearch/neuralsearch/search/query/exception/HybridSearchRescoreQueryException.java

@@ -0,0 +1,17 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package org.opensearch.neuralsearch.search.query.exception;
+
+import org.opensearch.OpenSearchException;
+
+/**
+ * Exception thrown when there is an issue with the hybrid search rescore query.
+ */
+public class HybridSearchRescoreQueryException extends OpenSearchException {
+
+    public HybridSearchRescoreQueryException(Throwable cause) {
+        super("rescore failed for hybrid query", cause);
+    }
+}

src/test/java/org/opensearch/neuralsearch/search/query/HybridCollectorManagerTests.java

@@ -5,6 +5,8 @@
 package org.opensearch.neuralsearch.search.query;
 
 import com.carrotsearch.randomizedtesting.RandomizedTest;
+
+import java.io.IOException;
 import java.util.Arrays;
 import lombok.SneakyThrows;
 import org.apache.lucene.document.FieldType;
@@ -47,6 +49,7 @@
 import org.opensearch.neuralsearch.search.collector.HybridTopScoreDocCollector;
 import org.opensearch.neuralsearch.search.collector.PagingFieldCollector;
 import org.opensearch.neuralsearch.search.collector.SimpleFieldCollector;
+import org.opensearch.neuralsearch.search.query.exception.HybridSearchRescoreQueryException;
 import org.opensearch.search.DocValueFormat;
 import org.opensearch.search.internal.ContextIndexSearcher;
 import org.opensearch.search.internal.SearchContext;
@@ -66,6 +69,7 @@
 
 import org.opensearch.search.rescore.QueryRescorerBuilder;
 import org.opensearch.search.rescore.RescoreContext;
+import org.opensearch.search.rescore.Rescorer;
 import org.opensearch.search.rescore.RescorerBuilder;
 import org.opensearch.search.sort.SortAndFormats;
 
@@ -1004,4 +1008,74 @@ public void testRescoreWithConcurrentSegmentSearch_whenMatchedDocsAndRescore_the
         reader2.close();
         directory2.close();
     }
+
+    @SneakyThrows
+    public void testReduceAndRescore_whenRescorerThrowsException_thenFail() {
+        SearchContext searchContext = mock(SearchContext.class);
+        QueryShardContext mockQueryShardContext = mock(QueryShardContext.class);
+        TextFieldMapper.TextFieldType fieldType = (TextFieldMapper.TextFieldType) createMapperService().fieldType(TEXT_FIELD_NAME);
+        when(mockQueryShardContext.fieldMapper(eq(TEXT_FIELD_NAME))).thenReturn(fieldType);
+
+        HybridQuery hybridQueryWithTerm = new HybridQuery(
+            List.of(
+                QueryBuilders.termQuery(TEXT_FIELD_NAME, QUERY1).toQuery(mockQueryShardContext),
+                QueryBuilders.termQuery(TEXT_FIELD_NAME, QUERY2).toQuery(mockQueryShardContext)
+            )
+        );
+        when(searchContext.query()).thenReturn(hybridQueryWithTerm);
+        ContextIndexSearcher indexSearcher = mock(ContextIndexSearcher.class);
+        IndexReader indexReader = mock(IndexReader.class);
+        when(indexReader.numDocs()).thenReturn(3);
+        when(indexSearcher.getIndexReader()).thenReturn(indexReader);
+        when(searchContext.searcher()).thenReturn(indexSearcher);
+        when(searchContext.size()).thenReturn(2);
+        IndexReaderContext indexReaderContext = mock(IndexReaderContext.class);
+        when(indexReader.getContext()).thenReturn(indexReaderContext);
+
+        Map<Class<?>, CollectorManager<? extends Collector, ReduceableSearchResult>> classCollectorManagerMap = new HashMap<>();
+        when(searchContext.queryCollectorManagers()).thenReturn(classCollectorManagerMap);
+        when(searchContext.shouldUseConcurrentSearch()).thenReturn(false);
+
+        Directory directory = newDirectory();
+        final IndexWriter w = new IndexWriter(directory, newIndexWriterConfig(new MockAnalyzer(random())));
+        FieldType ft = new FieldType(TextField.TYPE_NOT_STORED);
+        ft.setIndexOptions(random().nextBoolean() ? IndexOptions.DOCS : IndexOptions.DOCS_AND_FREQS);
+        ft.setOmitNorms(random().nextBoolean());
+        ft.freeze();
+
+        int docId1 = RandomizedTest.randomInt();
+        w.addDocument(getDocument(TEXT_FIELD_NAME, docId1, TEST_DOC_TEXT1, ft));
+        w.flush();
+        w.commit();
+
+        IndexReader reader = DirectoryReader.open(w);
+        IndexSearcher searcher = newSearcher(reader);
+
+        RescoreContext rescoreContext = mock(RescoreContext.class);
+        Rescorer rescorer = mock(Rescorer.class);
+        when(rescoreContext.rescorer()).thenReturn(rescorer);
+        when(rescorer.rescore(any(), any(), any())).thenThrow(new IOException("something happened with rescorer"));
+        List<RescoreContext> rescoreContexts = List.of(rescoreContext);
+        when(searchContext.rescore()).thenReturn(rescoreContexts);
+
+        CollectorManager hybridCollectorManager1 = HybridCollectorManager.createHybridCollectorManager(searchContext);
+        HybridTopScoreDocCollector collector = (HybridTopScoreDocCollector) hybridCollectorManager1.newCollector();
+
+        Weight weight = new HybridQueryWeight(hybridQueryWithTerm, searcher, ScoreMode.TOP_SCORES, BoostingQueryBuilder.DEFAULT_BOOST);
+        collector.setWeight(weight);
+
+        LeafReaderContext leafReaderContext = searcher.getIndexReader().leaves().get(0);
+        LeafCollector leafCollector = collector.getLeafCollector(leafReaderContext);
+
+        BulkScorer scorer = weight.bulkScorer(leafReaderContext);
+        scorer.score(leafCollector, leafReaderContext.reader().getLiveDocs());
+        leafCollector.finish();
+
+        expectThrows(HybridSearchRescoreQueryException.class, () -> hybridCollectorManager1.reduce(List.of()));
+
+        // release resources
+        w.close();
+        reader.close();
+        directory.close();
+    }
 }