[TD-2342]<fix>: disallow cross db create child table

src/mnode/src/mnodeTable.c

@@ -1734,6 +1734,16 @@ static int32_t mnodeDoCreateChildTable(SMnodeMsg *pMsg, int32_t tid) {
 
   if (pTable->info.type == TSDB_CHILD_TABLE) {
     STagData *pTagData = (STagData *)pCreate->schema;  // it is a tag key
+
+    char prefix[64] = {0};
+    int32_t prefixLen = tableIdPrefix(pMsg->pDb->name, prefix, 64);
+    if (0 != strncasecmp(prefix, pTagData->name, prefixLen)) {
+      mError("msg:%p, app:%p table:%s, corresponding super table:%s not in this db", pMsg, pMsg->rpcMsg.ahandle,
+             pCreate->tableId, pTagData->name);
+      mnodeDestroyChildTable(pTable);
+      return TSDB_CODE_MND_INVALID_TABLE_NAME;
+    }
+
     if (pMsg->pSTable == NULL) pMsg->pSTable = mnodeGetSuperTable(pTagData->name);
     if (pMsg->pSTable == NULL) {
       mError("msg:%p, app:%p table:%s, corresponding super table:%s does not exist", pMsg, pMsg->rpcMsg.ahandle,