[Backport 2.17] [Backport 2.x] fix wildcard term & terms query & add YAML REST test

CHANGELOG.md

@@ -98,6 +98,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Fix split response processor not included in allowlist ([#15393](https://github.com/opensearch-project/OpenSearch/pull/15393))
 - Fix unchecked cast in dynamic action map getter ([#15394](https://github.com/opensearch-project/OpenSearch/pull/15394))
 - Fix null values indexed as "null" strings in flat_object field ([#14069](https://github.com/opensearch-project/OpenSearch/pull/14069))
+- Fix terms query on wildcard field returns nothing ([#15607](https://github.com/opensearch-project/OpenSearch/pull/15607))
 
 ### Security
 

rest-api-spec/src/main/resources/rest-api-spec/test/search/270_wildcard_fieldtype_queries.yml

@@ -227,3 +227,13 @@ setup:
               my_field:
                 value: ".*"
   - match: { hits.total.value: 5 }
+---
+"terms query on wildcard field matches":
+  - do:
+      search:
+        index: test
+        body:
+          query:
+            terms: { my_field: ["AbCd"] }
+  - match: { hits.total.value: 1 }
+  - match: { hits.hits.0._id: "5" }

server/src/main/java/org/opensearch/index/mapper/WildcardFieldMapper.java

@@ -635,7 +635,7 @@
 
         @Override
         public Query termQueryCaseInsensitive(Object value, QueryShardContext context) {
-            return wildcardQuery(value.toString(), MultiTermQuery.CONSTANT_SCORE_REWRITE, true, context);
+            return wildcardQuery(BytesRefs.toString(value), MultiTermQuery.CONSTANT_SCORE_REWRITE, true, context);
         }
 
         @Override
@@ -649,7 +649,7 @@
             Set<String> expectedValues = new HashSet<>();
             StringBuilder pattern = new StringBuilder();
             for (Object value : values) {
-                String stringVal = value.toString();
+                String stringVal = BytesRefs.toString(value);
                 builder.add(matchAllTermsQuery(name(), getRequiredNGrams(stringVal)), BooleanClause.Occur.SHOULD);
                 expectedValues.add(stringVal);
                 if (pattern.length() > 0) {