QVX Connector & SQLCOLUMNS

[d_pranskus]

Hi

I have created a QVX custom connector using QVX SDK. Everything works fine except I am unable to run SQLCOLUMNS against that connection. IF I run that command I get the following message

QVX_UNKNOWN_ERROR: The given key was not present in the dictionary.. Stack trace written to C:\ProgramData\QlikTech\Custom Data\CurrencyRateConnector\Log\StackTrace.txt

SQLCOLUMNS

Is there anything I can do to enable that functionality. Can you give short example?

Thanks

Darius

[antrtiz001]

Hi,

as far as I know, you should interpret the SQLColumns, SQLTables or SQLTypes statements overriding the ExtractQuery method:

public override QvxDataTable ExtractQuery(string query, List<QvxTable> tables)
{
  // here you should get the query and give back a QvxDataTable object
  // get _tableName from query and find the table in the preloaded tablelist
  // or alternatively, create a new QvxTable object designed for SQLColumns.
  string tableName = "";
  QvxTable table = this.FindTable(tableName, tables);
  if (table == null)
  {
    QvxLog.Log(QvxLogFacility.Application, QvxLogSeverity.Error, string.Format("ExtractQueryAndTransmitTableHeader() - QvxPleaseSendReplyException({0}, \"Table not found: {1}\")", QvxResult.QVX_TABLE_NOT_FOUND, _tableName));
   throw new QvxPleaseSendReplyException(QvxResult.QVX_TABLE_NOT_FOUND, string.Format("Table not found: {0}", _tableName));
  }
  QvxDataTable table2 = new QvxDataTable(table);
  return table2;
}

Hope this helps.

Antonio

[d_pranskus]

Thanks Antonio

I tried this, but in case of SQLColumns command, the connector raises an error before it reaches ExtractQuery.

I put an MsgBox call as first line to display the query and it works fine for SQL SELECT, event for SQL COLUMNS (see space after SQL), but not for SQLCOLUMNS.

Could it be that the command must start with SQL (space) to be recognized as a valid command?

Cheers

Darius

[antrtiz001]

Hi Darius,

you are almost right: try putting the statement:

SELECT SQLColumns; 

Then it will enter the ExtractQuery method (tested on my qvx connector). here's the first fragment of ExtractQuery

public override QvxDataTable ExtractQuery(string query, List<QvxTable> tables)  
{ 
  MessageBox.Show("Query:"+query);  
  QvxLog.Log(QvxLogFacility.Application, QvxLogSeverity.Notice, "Internal ExtractQuery");  
  ... 

Antonio

[d_pranskus]

Hi Antonio

SELECT SQLColumns is not exactly the same command as SQLCOLUMNS. Say If you run SELECT SQLColumns against MS SQL server it will end up with an error. I am building reusable library and I need exact SQLColumns command to work.

Thanks

Darius

[antrtiz001]

Darius,

that's true. The problem is that you are passed to the ExtractQuery method when the parser reaches a select that can be run against the connector.

You can even try using a statement like

SQL SQLColumns;

this also passes through the ExtractQuery method, but you need to identify which statements should be parsed by the custom connector.

For example, when connecting to AS/400 through ODBC driver, every select statement will be preceded by the SQL reserved word:

SQL SELECT
    FLD1,   
    FLD2,
    FLD3
FROM TAB01;

Antonio