Q153807: PRB: GetRowsEx Re-fetches Last Read Record in Subsequent Calls

Article: Q153807
Product(s): Microsoft C Compiler
Version(s): winnt:
Operating System(s): 
Keyword(s): kbDAOsearch
Last Modified: 30-JUL-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- The DAO SDK, included with:
   - Microsoft Visual C++, versions 4.0, 4.1, 4.2 
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SYMPTOMS
========

The DAO SDK defines a function called GetRowsEx() that is a method of the DAO
recordset object. Unlike the GetRows() method, the GetRowsEx() method does not
advance to the next unread record after calling it. Instead, it begins fetching
with the last record fetched or the current record. For example, if you have 10
records in a resultset and you are fetching 5 of them at a time using
GetRowsEx(), you will see that record #5 gets fetched twice, once for each
GetRowsEx() call. Records 1 through 5 will be fetched in the first call to
GetRowsEx() and records 5 through 10 will be fetched in the second call to
GetRowsEx().

RESOLUTION
==========

Call MoveNext() for the recordset before executing the next call to GetRowsEx().
The MoveNext() call will make the next unread record the current record.

STATUS
======

This behavior is by design.

MORE INFORMATION
================

Steps to Reproduce Problem
--------------------------

Modify the DoGetRowsEx() function in GETRDLG.CPP contained in the GETROWS DAO SDK
sample. Change the code to the following:

   // Perform C++ GetRowsEx against the Employee table
     void CGetRowsDlg::DoGetRowsEx()
     {
         LPEMP           pEmpRows = new EMP[MAX_EMP_REC];
         CListBox        *pListBox =
                          (CListBox *)GetDlgItem(IDD_GETROWSLISTEX);
         CString         strLBRow;
         TCHAR           szId[16];
         LONG            lNumRecords;
         LONG            lCount;
         TCHAR           pBuf[MAX_EMP_REC * 15];

         //Perform GetRows on Employee table
         //This GetRows uses a specific C++ structure
         while (!m_cEmpRecordSet.GetEOF())
         {
         try
             {
             lNumRecords = m_cEmpRecordSet.GetRowsEx(pEmpRows, sizeof(EMP),
                   &Bindings[0], sizeof(Bindings) / sizeof(DAORSETBINDING),
                             pBuf, sizeof(pBuf),
                             2); // fetch 2 records at a time
             }
         catch (CdbException e)
             {
          //Differentiate between GetRowsEx Errors and other CdbExceptions
          // see defines in DAOGETRW.H
             if( e.m_hr == E_ROWTOOSHORT ||
                 e.m_hr == E_BADBINDINFO ||
                 e.m_hr == E_COLUMNUNAVAILABLE )
                 {
                 AfxMessageBox(_T("Error in GetRowsEx call."));
                 }
             else
                 {
                 AfxMessageBox(_T("General CdbException"));
                 }
             delete [] pEmpRows;
             return;
             }

         //Step through the returned rows
         for (lCount = 0; lCount < lNumRecords; lCount++)
             {
             strLBRow.Empty();
             wsprintf(szId, _T("%d,  "), pEmpRows[lCount].lEmpId);
             strLBRow += szId;
             strLBRow += pEmpRows[lCount].strLastName;
             strLBRow += _T(", ");
             strLBRow += (LPCTSTR) pEmpRows[lCount].strFirstName;
             pListBox->AddString(strLBRow);
             }
         }
         delete [] pEmpRows;
     }

To fix the code above, add a MoveNext at the end of the 'while' loop.

Additional query words: 4.00 4.10 4.20

======================================================================
Keywords          : kbDAOsearch 
Technology        : kbAudDeveloper kbDAOsearch kbSDKDAOSearch kbSDKSearch
Version           : winnt:

=============================================================================

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