diff --git a/src/mnode/src/mnodeDb.c b/src/mnode/src/mnodeDb.c
index c13cd7c95c5fdeca05934c42634b2dfa18bdabb7..8c74c9413d9eb07dcf4420c6c9e223ffd28a6247 100644
--- a/src/mnode/src/mnodeDb.c
+++ b/src/mnode/src/mnodeDb.c
@@ -179,9 +179,14 @@ void mnodeDecDbRef(SDbObj *pDb) {
 
 SDbObj *mnodeGetDbByTableId(char *tableId) {
   char db[TSDB_TABLE_ID_LEN], *pos;
-
+ 
+  // tableId format should be :  acct.db.table
   pos = strstr(tableId, TS_PATH_DELIMITER);
+  assert(NULL != pos);
+
   pos = strstr(pos + 1, TS_PATH_DELIMITER);
+  assert(NULL != pos);
+
   memset(db, 0, sizeof(db));
   strncpy(db, tableId, pos - tableId);