Fix UOE when building exists query for nested search-as-you-type field (#64630)

PrefixFieldType can use the default existsQuery() implementation.

Fixes #64609

Author: romseygeek

modules/mapper-extras/src/main/java/org/elasticsearch/index/mapper/SearchAsYouTypeFieldMapper.java

@@ -394,11 +394,6 @@ public String typeName() {
         public String toString() {
             return super.toString() + ",prefixChars=" + minChars + ":" + maxChars;
         }
-
-        @Override
-        public Query existsQuery(QueryShardContext context) {
-            throw new UnsupportedOperationException();
-        }
     }
 
     static final class PrefixFieldMapper extends FieldMapper {

modules/mapper-extras/src/test/java/org/elasticsearch/index/mapper/SearchAsYouTypeFieldMapperTests.java

@@ -26,18 +26,21 @@
 import org.apache.lucene.index.IndexableField;
 import org.apache.lucene.index.IndexableFieldType;
 import org.apache.lucene.index.Term;
+import org.apache.lucene.queryparser.classic.ParseException;
 import org.apache.lucene.search.BooleanClause;
 import org.apache.lucene.search.BooleanQuery;
 import org.apache.lucene.search.ConstantScoreQuery;
 import org.apache.lucene.search.DisjunctionMaxQuery;
 import org.apache.lucene.search.MatchNoDocsQuery;
 import org.apache.lucene.search.MultiPhraseQuery;
+import org.apache.lucene.search.NormsFieldExistsQuery;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.search.SynonymQuery;
 import org.apache.lucene.search.TermQuery;
 import org.apache.lucene.search.spans.FieldMaskingSpanQuery;
 import org.apache.lucene.search.spans.SpanNearQuery;
 import org.apache.lucene.search.spans.SpanTermQuery;
+import org.elasticsearch.Version;
 import org.elasticsearch.common.lucene.search.MultiPhrasePrefixQuery;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.index.IndexSettings;
@@ -54,6 +57,7 @@
 import org.elasticsearch.index.query.MatchPhraseQueryBuilder;
 import org.elasticsearch.index.query.MultiMatchQueryBuilder;
 import org.elasticsearch.index.query.QueryShardContext;
+import org.elasticsearch.index.search.QueryStringQueryParser;
 import org.elasticsearch.plugins.Plugin;
 
 import java.io.IOException;
@@ -74,6 +78,7 @@
 import static org.hamcrest.Matchers.hasSize;
 import static org.hamcrest.Matchers.notNullValue;
 import static org.hamcrest.core.IsInstanceOf.instanceOf;
+import static org.mockito.Mockito.when;
 
 public class SearchAsYouTypeFieldMapperTests extends MapperTestCase {
 
@@ -534,6 +539,35 @@ public void testMatchPhrase() throws IOException {
         }
     }
 
+    public void testNestedExistsQuery() throws IOException, ParseException {
+        MapperService ms = createMapperService(mapping(b -> {
+            b.startObject("foo");
+            {
+                b.field("type", "object");
+                b.startObject("properties");
+                {
+                    b.startObject("bar");
+                    {
+                        b.field("type", "search_as_you_type");
+                    }
+                    b.endObject();
+                }
+                b.endObject();
+            }
+            b.endObject();
+        }));
+        QueryShardContext qsc = createQueryShardContext(ms);
+        when(qsc.indexVersionCreated()).thenReturn(Version.CURRENT);
+        QueryStringQueryParser parser = new QueryStringQueryParser(qsc, "f");
+        Query q = parser.parse("foo:*");
+        assertEquals(new ConstantScoreQuery(new BooleanQuery.Builder()
+            .add(new NormsFieldExistsQuery("foo.bar"), BooleanClause.Occur.SHOULD)
+            .add(new NormsFieldExistsQuery("foo.bar._3gram"), BooleanClause.Occur.SHOULD)
+            .add(new NormsFieldExistsQuery("foo.bar._2gram"), BooleanClause.Occur.SHOULD)
+            .add(new TermQuery(new Term("_field_names", "foo.bar._index_prefix")), BooleanClause.Occur.SHOULD)
+            .build()), q);
+    }
+
     private static BooleanQuery buildBoolPrefixQuery(String shingleFieldName, String prefixFieldName, List<String> terms) {
         final BooleanQuery.Builder builder = new BooleanQuery.Builder();
         for (int i = 0; i < terms.size() - 1; i++) {

test/framework/src/main/java/org/elasticsearch/index/mapper/MapperServiceTestCase.java

@@ -401,6 +401,8 @@ protected QueryShardContext createQueryShardContext(MapperService mapperService)
             .thenAnswer(inv -> mapperService.fieldType(inv.getArguments()[0].toString()) != null);
         when(queryShardContext.getIndexAnalyzers()).thenReturn(mapperService.getIndexAnalyzers());
         when(queryShardContext.getIndexSettings()).thenReturn(mapperService.getIndexSettings());
+        when(queryShardContext.getObjectMapper(anyString())).thenAnswer(
+            inv -> mapperService.getObjectMapper(inv.getArguments()[0].toString()));
         when(queryShardContext.simpleMatchToIndexNames(anyObject())).thenAnswer(
             inv -> mapperService.simpleMatchToFullName(inv.getArguments()[0].toString())
         );