Fix IT

Signed-off-by: Peng Huo <[email protected]>

flint-core/src/main/scala/org/opensearch/flint/core/storage/FlintOpenSearchClient.java

@@ -60,7 +60,7 @@ public class FlintOpenSearchClient implements FlintClient {
    * excluding '*' because it's reserved for pattern matching.
    */
   private final static Set<Character> INVALID_INDEX_NAME_CHARS =
-      Set.of(' ', ':', '"', '+', '/', '\\', '|', '?', '#', '>', '<');
+      Set.of(' ', ',', ':', '"', '+', '/', '\\', '|', '?', '#', '>', '<');
 
   private final FlintOptions options;
 
@@ -167,7 +167,9 @@ public void deleteIndex(String indexName) {
   /**
    * Create {@link FlintReader}.
    *
-   * @param indexName index name.
+   * FIXME: should indexName limit to single index? revisit this when add index partition.
+   *
+   * @param indexName index name. index name could be single index name, comma separate index.
    * @param query     DSL query. DSL query is null means match_all.
    * @return {@link FlintReader}.
    */
@@ -183,7 +185,8 @@ public FlintReader createReader(String indexName, String query) {
         queryBuilder = AbstractQueryBuilder.parseInnerQueryBuilder(parser);
       }
       return new OpenSearchScrollReader(createClient(),
-          sanitizeIndexName(indexName),
+          String.join(",",
+              Arrays.stream(indexName.split(",")).map(this::sanitizeIndexName).toArray(String[]::new)),
           new SearchSourceBuilder().query(queryBuilder),
           options);
     } catch (IOException e) {