PRB: ATL Consumer Wizard Code Truncates SQL Server text field to a 1024 TCHAR Array

ID: Q234146

The information in this article applies to:

Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0

SYMPTOMS

The ATL consumer wizard maps DBTYPE_STR fields, such as SQL Server's text fields, to TCHAR arrays of 1024 bytes instead of an ISequentialStream pointer. The data for the columns is truncated to 1024 bytes.

CAUSE

This behavior is by design.

RESOLUTION

If data larger than 1024 is expected, you can increase the size of the array in your accessor class. For example, by default your code may look like the following:


TCHAR m_TextColumn[1024];
...
COLUMN_ENTRY(3, m_TextColumn);

Change the 1024 to the desired maximum length of the data.

Another alternative is to use ISequentialStream to retrieve and set the data. ISequentialStream allows an application to read and write pieces at a time and a predefined maximum buffer size is not required. You would change the code above to:


ISequentialStream * m_TextColumn;
...
BLOB_ENTRY(3, IID_ISequentialStream, STGM_READ,m_TextColumn);

REFERENCES

See Q190958 AOTBLOB for example of how to read and update using an ISequentialStream pointer.

Additional query words:

Keywords : kbwizard kbATL210bug kbDatabase kbSQL kbATL300bug kbGrpVCDB
Version : WINDOWS:6.0
Platform : WINDOWS
Issue type : kbprb