fix concat expr error (#1059)

Signed-off-by: ShYang <shaung.yang2@microfocus.com>
Co-authored-by: ShYang <shaung.yang2@microfocus.com>

src/main/java/io/milvus/orm/iterator/QueryIterator.java

@@ -166,7 +166,7 @@ public class QueryIterator {
         if (StringUtils.isEmpty(currentExpr)) {
             return filteredPKStr;
         }
-        return currentExpr + " and " + filteredPKStr;
+        return " ( "+currentExpr+" ) " + " and " + filteredPKStr;
     }
 
     private boolean isResSufficient(List<QueryResultsWrapper.RowRecord> ret) {