Insufficient privilege: Not authorized at ptime/query/checker/query_check.cc on hdbsequence

Question

Hi All,
I am currently trying to create a table (TOPIC) and a sequence (SEQ_TOPIC_ID) in HCP, and a XSJS service on top of it to insert a entry to the table.
In my XS project, I placed a TOPIC.hdbtable and SEQ_TOPIC_ID.hdbsequence in it. Both table and sequence are generated correctly in my trial account schema in the hana db.
Then,in order to grant the access to the table and sequence , I also placed a file model_access.hdbrole in the project folder.
The content looks like follow:
role i065831trial.bubuwork.TopicCenter::model_access {
    application privilege: i065831trial.bubuwork.TopicCenter::Basic;
    sql object i065831trial.bubuwork.TopicCenter::TOPIC : SELECT,INSERT;
    sql object i065831trial.bubuwork.TopicCenter::SEQ_TOPIC_ID : SELECT, DROP;
The issue is, when I call the XSJS service from the web url, I will facing below error:
Error while executing query: [dberror(Connection.prepareStatement): 258 - insufficient privilege: Not authorized at ptime/query/checker/query_check.cc:2547]
the role has been granted to my account, and I am able to insert to the table TOPIC without sequence with above role setting, but If I try to read the SEQ_TOPIC_ID, an insufficient privilege will shown up.
My question is: Is following line correct to grant the privilege to a role for sequence ? It does not seem to work for sequence  !
sql object i065831trial.bubuwork.TopicCenter::SEQ_TOPIC_ID : SELECT, DROP;
Thanks very much!

Answer 1

Thanks Thomas for your reply, firstly I tried to embed my sequence in the insert SQL, as the problem happened. I pulled out the sequence into a single query string, like blow:
var select_topic_next_val = "select \"i065831trial.bubuwork.TopicCenter::SEQ_TOPIC_ID\".nextval as seqid from dummy";
function close(closables) {
    var closable; 
    var i; 
    for (i = 0; i < closables.length; i++) { 
              closable = closables[i]; 
              if(closable) { 
                        closable.close(); 
function insertTopic(xargs){
    var connection = $.db.getConnection(); 
    var statement = null;
    var resultSet = null;
    try{
        //get next sequence id
        statement = connection.prepareStatement(select_topic_next_val);
        resultSet = statement.executeQuery();
        while(resultSet.next()){
            var seqId = resultSet.getString(1);
            break;
//        statement = connection.prepareStatement(insert_topic_sql);
//        statement.setString(1,seqId);
//        statement.setString(2,xargs.owner);
//        statement.setString(3,xargs.approver);
//        statement.setString(4,xargs.name);
//        statement.setString(5,xargs.status);
//        statement.setString(6,xargs.description);
//        //statement.setTimestamp(6,xargs.lastModify);
//        statement.setTimestamp(7,null);
//        statement.setDate(8,xargs.begda);
//        statement.setDate(9,xargs.endda);
//        statement.setString(10,xargs.keyword);
//        statement.executeUpdate();
    }finally { 
        close([resultSet, statement, connection]);