DOCUMENT:Q139511 30-JUL-2001 [visualc] TITLE :FIX: Text Data Truncated When Using optimizeBulkAdd PRODUCT :Microsoft C Compiler PROD/VER:1.52a 1.52b OPER/SYS: KEYWORDS:kbDatabase kbMFC kbODBC kbVCkbbuglist kbfixlist ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - The Microsoft Foundation Classes (MFC), included with: - Microsoft Visual C++ for Windows, 16-bit edition, versions 1.52a, 1.52b ------------------------------------------------------------------------------- SYMPTOMS ======== When you try to use the optimizeBulkAdd flag with a CRecordset object, text fields may be truncated. For example, if the first insertion in the table inserts a text value in field1 that is four characters long and a second insertion inserts a text value in field1 that is five characters, the text in the second insertion will be truncated to four characters, the length of the text from the first insertion. CAUSE ===== MFC is incorrectly binding the length of the parameters it uses in the INSERT INTO statement it constructs for adding a record. RESOLUTION ========== Use either of these two workarounds: - As the first record you add, insert a dummy record that contains strings with the maximum length you want for the text fields in the recordset. Every record after this first insertion will always have text values with lengths that are less than or equal to the length of the text fields in the dummy record. When you have finished inserting records, delete the dummy record. -or- - Replace the RFX_Text() function calls in your CRecordset's DoFieldExchange() with the following RFX_Text2() function, which performs the correct binding for the parameters used in the INSERT INTO statement used internally by MFC to add a record. In your recordset's header file add: void RFX_Text2(CFieldExchange* pFX, const char* szName, CString& value, int nMaxLength=255, int nColumnType=SQL_VARCHAR); In your recordset's .cpp file add: void RFX_Text2(CFieldExchange* pFX, const char* szName, CString& value, int nMaxLength /*=255*/ , int nColumnType /* =SQL_VARCHAR */) { if (pFX->m_nOperation != CFieldExchange::NameValue && pFX->m_nOperation != CFieldExchange::Value && pFX->m_nOperation != CFieldExchange::BindParam) { RFX_Text(pFX, szName, value, nMaxLength, nColumnType); return; } ASSERT(AfxIsValidAddress(pFX, sizeof(CFieldExchange))); ASSERT(AfxIsValidString(szName)); ASSERT(AfxIsValidAddress&value, sizeof(CString))); RETCODE nRetCode; UINT nField; if (!pFX->IsFieldType(&nField)) return; LONG* plLength = pFX->m_prs->GetFieldLength(pFX); switch (pFX->m_nOperation) { case CFieldExchange::NameValue: if (pFX->m_prs->IsFieldFlagDirty(nField,pFX->m_nFieldType)) { *pFX->m_pstr += pFX->m_prs->m_pDatabase->QuoteName(szName); *pFX->m_pstr += "="; } // Fall through case CFieldExchange::Value: if (pFX->m_prs->IsFieldFlagDirty(nField, pFX->m_nFieldType)) { // If user marked column NULL, reflect this in length if (pFX->m_prs->IsFieldFlagNull(nField, pFX->m_nFieldType)) *plLength = SQL_NULL_DATA; else *plLength = SQL_NTS; // If optimizing for bulk add, just set length. if (!(pFX->m_prs->m_dwOptions & CRecordset::optimizeBulkAdd)) { *pFX->m_pstr += "?"; *pFX->m_pstr += pFX->m_lpszSeparator; pFX->m_nParamFields++; AFX_SQL_SYNC(::SQLSetParam(pFX->m_hstmt, (unsigned short int)pFX->m_nParamFields, SQL_C_CHAR, (short int)nColumnType, nMaxLength, 0, value.GetBuffer(0), plLength)); value.ReleaseBuffer(); if (nRetCode != SQL_SUCCESS) pFX->m_prs->ThrowDBException(nRetCode, pFX->m_hstmt); } } return; case CFieldExchange::BindParam: *plLength = SQL_NTS; // Preallocate to nMaxLength value.GetBufferSetLength(nMaxLength); AFX_SQL_SYNC(::SQLSetParam(pFX->m_hstmt, (unsigned short int)nField, (short int)SQL_C_CHAR, (short int)nColumnType, nMaxLength, 0, value.GetBuffer(0), plLength)); value.ReleaseBuffer(); if (nRetCode != SQL_SUCCESS) pFX->m_prs->ThrowDBException(nRetCode, pFX->m_hstmt); return; } } STATUS ====== Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. The code has been corrected in Visual C++ version 2.2 and later. MORE INFORMATION ================ Sample Code to Reproduce Problem -------------------------------- CMyRecordSet rs; rs.Open(CRecordset::snapshot, NULL, CRecordset::optimizeBulkAdd); rs.AddNew(); rs.m_field1="1234"; rs.Update(); rs.AddNew(); rs.m_field1="12345"; rs.Update(); rs.Close(); The table will look like this: field1 ------ 1234 1234 instead of this: field1 ------ 1234 12345 REFERENCES ========== See the following references for more information about the problem and workaround: - SQLSetParam() documentation in the ODBC 1.0 Programmer's Reference or SQLBindParameter() in the ODBC 2.0 Programmer's Reference. - For more information about bulk add optimizations in MFC, please see the following article in the Microsoft Knowledge Base: Q126131 How to Speed Up Apps that Use Microsoft Access 2.0 ODBC Driver Following is the information from the Msetup.hlp file on the Visual C++ compact disc that talks about the optimizeBulkAdd feature: The MFC CRecordset class has a new optimization (in both 16- and 32-bit versions) that improves efficiency when you're adding new records in bulk to a table. A new option for the dwOptions parameter to the CRecordset::Open member function, optimizeBulkAdd, improves performance when you're adding multiple records consecutively without calling Requery or Close. Only those fields that are "dirty" prior to the first Update call are marked as "dirty" for subsequent AddNew/Update calls. If you are using the database classes to take advantage of the ::SQLSetPos API function for adding, editing, and deleting records, this optimization is unnecessary. If the ODBC Cursor Library is loaded or the ODBC driver doesn't support adding, editing, and deleting via ::SQLSetPos, this optimization should improve bulk add performance. To turn on this optimization, set the dwOptions parameter in the Open call for your recordset to: appendOnly | optimizeBulkAdd Additional query words: 1.5 1.50 1.52 ====================================================================== Keywords : kbDatabase kbMFC kbODBC kbVC kbbuglist kbfixlist Technology : kbAudDeveloper kbMFC Version : 1.52a 1.52b Issue type : kbbug Solution Type : kbfix ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2001.