What is the problem with this code?

Igor Korot wrote:

SQLWCHAR *qry1 = new SQLWCHAR[query1.length() + 2];
memset( qry1, '\0', query1.length() + 2 );

memset expects the length to be in bytes.

ret = SQLPrepare( m_hstmt, qry1, SQL_NTS );
ret = SQLDescribeCol( m_hstmt, 1, columnName, 256, &columnNameLen, &columnDataType, &columnDataSize, &columnDataDigits, &columnDataNullable );

The SQLDescribeCol() call fails with the error invalid column number".

Does SQLExecute work? Does SQLNumResultCols give 1?

The specification says "for performance reasons, an application should
not call SQLDescribeCol before executing a statement." But it should
work anyway; if not, this would be a bug. What are the settings of
"Parse Statements" and "Server side prepare" of the data source?

Regards,
Clemens

Does anybody have an idea why the code below fails?

Thank you.

---------- Forwarded message ---------
From: Igor Korot <ikorot01@gmail.com>
Date: Thu, Oct 18, 2018 at 11:49 PM
Subject: What is the problem with this code?
To: PostgreSQL ODBC list <pgsql-odbc@postgresql.org>

Hi, ALL,

[code]
std::wstring query1 = L"SHOW log_directory";
std::wstring query2 = L"SHOW log_filename";
SQLWCHAR *qry1 = new SQLWCHAR[query1.length() + 2];
SQLWCHAR *qry2 = new SQLWCHAR[query2.length() + 2];
memset( qry1, '\0', query1.length() + 2 );
memset( qry2, '\0', query2.length() + 2 );
uc_to_str_cpy( qry1, query1 );
uc_to_str_cpy( qry2, query2 );
RETCODE ret = SQLAllocHandle( SQL_HANDLE_STMT, m_hdbc, &m_hstmt );
if( ret == SQL_SUCCESS || ret == SQL_SUCCESS_WITH_INFO )
{
ret = SQLPrepare( m_hstmt, qry1, SQL_NTS );
if( ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO )
{
GetErrorMessage( errorMsg, 1 );
result = 1;
}
else
{
ret = SQLDescribeCol( m_hstmt, 1, columnName, 256,
&columnNameLen, &columnDataType, &columnDataSize, &columnDataDigits,
&columnDataNullable );
if( ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO )
{
GetErrorMessage( errorMsg, 1 );
result = 1;
}
[/code]

The SQLDescribeCol() call fails with the error invalid column number".

Does anybody have any idea?

Thank you.

In your place I would double check whether the table structure on the
database is what you expect. Without knowing the code of mentioned
function there seem only two numbers in the call. It quite misty in
the crystal fortune telling ball to me.

Quoting Igor Korot <ikorot01@gmail.com>: