Fix synonym phrase query expansion for cross_fields parsing (#28045)

* Fix synonym phrase query expansion for cross_fields parsing

The `cross_fields` mode for query parser ignores phrase query generated by multi-word synonyms.
In such case only the first field of each analyzer group is kept. This change fixes this issue
by expanding the phrase query for each analyzer group to **all** fields using a disjunction max query.

server/src/main/java/org/elasticsearch/index/search/MatchQuery.java

@@ -29,6 +29,7 @@ import org.apache.lucene.search.BooleanClause;
 import org.apache.lucene.search.BooleanClause.Occur;
 import org.apache.lucene.search.BooleanQuery;
 import org.apache.lucene.search.BoostQuery;
+import org.apache.lucene.search.DisjunctionMaxQuery;
 import org.apache.lucene.search.FuzzyQuery;
 import org.apache.lucene.search.MultiPhraseQuery;
 import org.apache.lucene.search.MultiTermQuery;
@@ -350,7 +351,12 @@ public class MatchQuery {
                     throw exc;
                 }
             }
-            return super.analyzePhrase(field, stream, slop);
+            Query query = super.analyzePhrase(field, stream, slop);
+            if (query instanceof PhraseQuery) {
+                // synonyms that expand to multiple terms can return a phrase query.
+                return blendPhraseQuery((PhraseQuery) query, mapper);
+            }
+            return query;
         }
 
         /**
@@ -472,6 +478,14 @@ public class MatchQuery {
         }
     }
 
+    /**
+     * Called when a phrase query is built with {@link QueryBuilder#analyzePhrase(String, TokenStream, int)}.
+     * Subclass can override this function to blend this query to multiple fields.
+     */
+    protected Query blendPhraseQuery(PhraseQuery query, MappedFieldType fieldType) {
+        return query;
+    }
+
     protected Query blendTermsQuery(Term[] terms, MappedFieldType fieldType) {
         return new SynonymQuery(terms);
     }
@@ -494,5 +508,4 @@ public class MatchQuery {
         }
         return termQuery(fieldType, term.bytes(), lenient);
     }
-
 }

server/src/main/java/org/elasticsearch/index/search/MultiMatchQuery.java

@@ -25,10 +25,10 @@ import org.apache.lucene.queries.BlendedTermQuery;
 import org.apache.lucene.search.BoostQuery;
 import org.apache.lucene.search.DisjunctionMaxQuery;
 import org.apache.lucene.search.MatchNoDocsQuery;
+import org.apache.lucene.search.PhraseQuery;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.search.TermQuery;
 import org.apache.lucene.util.BytesRef;
-import org.elasticsearch.ElasticsearchParseException;
 import org.elasticsearch.common.lucene.search.Queries;
 import org.elasticsearch.index.mapper.MappedFieldType;
 import org.elasticsearch.index.query.AbstractQueryBuilder;
@@ -143,6 +143,10 @@ public class MultiMatchQuery extends MatchQuery {
         public Query termQuery(MappedFieldType fieldType, BytesRef value) {
             return MultiMatchQuery.this.termQuery(fieldType, value, lenient);
         }
+
+        public Query blendPhrase(PhraseQuery query, MappedFieldType type) {
+            return MultiMatchQuery.super.blendPhraseQuery(query, type);
+        }
     }
 
     final class CrossFieldsQueryBuilder extends QueryBuilder {
@@ -226,6 +230,17 @@ public class MultiMatchQuery extends MatchQuery {
              */
             return blendTerm(new Term(fieldType.name(), value.utf8ToString()), fieldType);
         }
+
+        @Override
+        public Query blendPhrase(PhraseQuery query, MappedFieldType type) {
+            if (blendedFields == null) {
+                return super.blendPhrase(query, type);
+            }
+            /**
+             * We build phrase queries for multi-word synonyms when {@link QueryBuilder#autoGenerateSynonymsPhraseQuery} is true.
+             */
+            return MultiMatchQuery.blendPhrase(query, blendedFields);
+        }
     }
 
     static Query blendTerm(QueryShardContext context, BytesRef value, Float commonTermsCutoff, float tieBreaker,
@@ -288,6 +303,28 @@ public class MultiMatchQuery extends MatchQuery {
         }
     }
 
+    /**
+     * Expand a {@link PhraseQuery} to multiple fields that share the same analyzer.
+     * Returns a {@link DisjunctionMaxQuery} with a disjunction for each expanded field.
+     */
+    static Query blendPhrase(PhraseQuery query, FieldAndFieldType... fields) {
+        List<Query> disjunctions = new ArrayList<>();
+        for (FieldAndFieldType field : fields) {
+            int[] positions = query.getPositions();
+            Term[] terms = query.getTerms();
+            PhraseQuery.Builder builder = new PhraseQuery.Builder();
+            for (int i = 0; i < terms.length; i++) {
+                builder.add(new Term(field.fieldType.name(), terms[i].bytes()), positions[i]);
+            }
+            Query q = builder.build();
+            if (field.boost != AbstractQueryBuilder.DEFAULT_BOOST) {
+                q = new BoostQuery(q, field.boost);
+            }
+            disjunctions.add(q);
+        }
+        return new DisjunctionMaxQuery(disjunctions, 0.0f);
+    }
+
     @Override
     protected Query blendTermQuery(Term term, MappedFieldType fieldType) {
         if (queryBuilder == null) {
@@ -304,6 +341,14 @@ public class MultiMatchQuery extends MatchQuery {
         return queryBuilder.blendTerms(terms, fieldType);
     }
 
+    @Override
+    protected Query blendPhraseQuery(PhraseQuery query, MappedFieldType fieldType) {
+        if (queryBuilder == null) {
+            return super.blendPhraseQuery(query, fieldType);
+        }
+        return queryBuilder.blendPhrase(query, fieldType);
+    }
+
     static final class FieldAndFieldType {
         final MappedFieldType fieldType;
         final float boost;

server/src/test/java/org/elasticsearch/index/search/MultiMatchQueryTests.java

@@ -19,12 +19,16 @@
 
 package org.elasticsearch.index.search;
 
+import org.apache.lucene.analysis.MockSynonymAnalyzer;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.queries.BlendedTermQuery;
+import org.apache.lucene.search.BooleanClause;
+import org.apache.lucene.search.BooleanQuery;
 import org.apache.lucene.search.BoostQuery;
 import org.apache.lucene.search.DisjunctionMaxQuery;
 import org.apache.lucene.search.MatchAllDocsQuery;
 import org.apache.lucene.search.MatchNoDocsQuery;
+import org.apache.lucene.search.PhraseQuery;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.search.SynonymQuery;
 import org.apache.lucene.search.TermQuery;
@@ -43,7 +47,11 @@ import org.elasticsearch.test.ESSingleNodeTestCase;
 import org.junit.Before;
 
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 
 import static org.elasticsearch.index.query.QueryBuilders.multiMatchQuery;
 import static org.hamcrest.Matchers.equalTo;
@@ -220,4 +228,45 @@ public class MultiMatchQueryTests extends ESSingleNodeTestCase {
         assertThat(parsedQuery, equalTo(expectedQuery));
 
     }
+
+    public void testMultiMatchCrossFieldsWithSynonymsPhrase() throws IOException {
+        QueryShardContext queryShardContext = indexService.newQueryShardContext(
+            randomInt(20), null, () -> { throw new UnsupportedOperationException(); }, null);
+        MultiMatchQuery parser = new MultiMatchQuery(queryShardContext);
+        parser.setAnalyzer(new MockSynonymAnalyzer());
+        Map<String, Float> fieldNames = new HashMap<>();
+        fieldNames.put("name.first", 1.0f);
+        fieldNames.put("name.last", 1.0f);
+        Query query = parser.parse(MultiMatchQueryBuilder.Type.CROSS_FIELDS, fieldNames, "guinea pig", null);
+
+        Term[] terms = new Term[2];
+        terms[0] = new Term("name.first", "cavy");
+        terms[1] = new Term("name.last", "cavy");
+        float[] boosts = new float[2];
+        Arrays.fill(boosts, 1.0f);
+
+        List<Query> phraseDisjuncts = new ArrayList<>();
+        phraseDisjuncts.add(
+            new PhraseQuery.Builder()
+                .add(new Term("name.first", "guinea"))
+                .add(new Term("name.first", "pig"))
+                .build()
+        );
+        phraseDisjuncts.add(
+            new PhraseQuery.Builder()
+                .add(new Term("name.last", "guinea"))
+                .add(new Term("name.last", "pig"))
+                .build()
+        );
+        BooleanQuery expected = new BooleanQuery.Builder()
+            .add(
+                new BooleanQuery.Builder()
+                    .add(new DisjunctionMaxQuery(phraseDisjuncts, 0.0f), BooleanClause.Occur.SHOULD)
+                    .add(BlendedTermQuery.dismaxBlendedQuery(terms, boosts, 1.0f), BooleanClause.Occur.SHOULD)
+                    .build(),
+                BooleanClause.Occur.SHOULD
+            )
+            .build();
+        assertEquals(expected, query);
+    }
 }