Read a FILESTREAM Column to File Using IBCPSession (OLE DB)

Artikel
04/03/2023

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW)

Download OLE DB driver

This sample reads a filestream column to a file using the IBCPSession interface and writes a format file.

For more information on the filestream feature, see FILESTREAM Support.

Example

Make sure your INCLUDE environment variable includes the directory that contains msoledbsql.h.

Use one of the following samples to create the table that this sample reads from:

Copy the first code listing and paste it into a file called ISSHelper.h.

Copy the second code listing and paste it into a file called ISSHelper.cpp.

Copy the third code listing and paste it into a file called IBCPSession.cpp.

Compile IBCPSession.cpp, ISSHelper.cpp, ole32.lib, and oleaut32.lib.

When this sample is run, you must pass a server name (or server\instance_name) and a name for the format file it will create.

// ISSHelper.h: interface for the CISSHelper class.  
  
#if !defined(AFX_ISSHELPER_H__7B88E5F3_263F_11D2_9D1F_00C04F96B8B2__INCLUDED_)  
#define AFX_ISSHELPER_H__7B88E5F3_263F_11D2_9D1F_00C04F96B8B2__INCLUDED_  
  
#if _MSC_VER > 1000  
#pragma once  
#endif // _MSC_VER > 1000  
  
class CISSHelper : public ISequentialStream  {  
public:  
   // Constructor/destructor.  
   CISSHelper(__int64 i64LobBytes);  
   virtual ~CISSHelper();  
  
   // Helper function to clean up memory.  
   virtual void Clear();  
  
   // ISequentialStream interface implementation.  
   STDMETHODIMP_(ULONG)AddRef(void);  
   STDMETHODIMP_(ULONG)Release(void);  
   STDMETHODIMP QueryInterface(REFIID riid, LPVOID *ppv);  
   STDMETHODIMP Read(   
      /* [out] */ void __RPC_FAR *pv,  
      /* [in] */ ULONG cb,  
      /* [out] */ ULONG __RPC_FAR *pcbRead);  
   STDMETHODIMP Write(   
      /* [in] */ const void __RPC_FAR *pv,  
      /* [in] */ ULONG cb,  
      /* [out] */ ULONG __RPC_FAR *pcbWritten);  
  
public:  
   void * m_pBuffer;   // Buffer  
   ULONG m_ulLength;   // Total buffer size.  
   ULONG m_ulStatus;   // Column status.  
  
   __int64 m_i64BytesUploaded;  
   __int64 m_i64LastPrintUploaded;  
   __int64 m_i64ThreshHold;  
   DWORD m_dwStartTick;  
   DWORD m_dwParamOrdinal;  
  
private:  
   ULONG m_cRef;   // Reference count (not used).  
   ULONG m_iReadPos;   // Current index position for reading from the buffer.  
   ULONG m_iWritePos;   // Current index position for writing to the buffer.  
};  
  
#endif // !defined(AFX_ISSHELPER_H__7B88E5F3_263F_11D2_9D1F_00C04F96B8B2__INCLUDED_)

// ISSHelper.cpp: implementation of the CISSHelper class.  
  
#pragma once  
#define WIN32_LEAN_AND_MEAN   // Exclude rarely-used stuff from Windows headers  
#include <stdio.h>  
#include <conio.h>  
#include <tchar.h>  
#include <msoledbsql.h>  
#include "ISSHelper.h"  
  
#ifdef _DEBUG  
#undef THIS_FILE  
static char THIS_FILE[]=__FILE__;  
#define new DEBUm_NEW  
#endif  
  
// Implementation of ISequentialStream interface  
CISSHelper::CISSHelper(__int64 i64LobBytes) {  
   m_cRef= 0;  
   m_pBuffer= NULL;  
   m_ulLength= 0;  
   m_ulStatus   = DBSTATUS_S_OK;  
   m_iReadPos= 0;  
   m_iWritePos= 0;  
   m_i64ThreshHold = i64LobBytes;  
   m_i64BytesUploaded = 0;  
   m_i64LastPrintUploaded = 0;  
   m_dwStartTick = 0;  
   m_dwParamOrdinal = 0;  
}  
  
CISSHelper::~CISSHelper() {  
   Clear();  
}  
  
void CISSHelper::Clear() {  
   CoTaskMemFree( m_pBuffer );  
   m_cRef= 0;  
   m_pBuffer= NULL;  
   m_ulLength= 0;  
   m_ulStatus   = DBSTATUS_S_OK;  
   m_iReadPos= 0;  
   m_iWritePos= 0;  
}  
  
ULONG CISSHelper::AddRef() {  
   return ++m_cRef;  
}  
  
ULONG CISSHelper::Release() {  
   return --m_cRef;  
}  
  
HRESULT CISSHelper::QueryInterface( REFIID riid, void** ppv ) {  
   *ppv = NULL;  
   if ( riid == IID_IUnknown )   
      *ppv = this;  
   if ( riid == IID_ISequentialStream )   
      *ppv = this;  
   if ( *ppv ) {  
      ( (IUnknown*) *ppv )->AddRef();  
      return S_OK;  
   }  
   return E_NOINTERFACE;  
}  
  
HRESULT CISSHelper::Read( void *pv, ULONG cb, ULONG* pcbRead ) {  
   // Check parameters.  
   if ( pcbRead )   
      *pcbRead = 0;  
   if ( !pv )   
      return STG_E_INVALIDPOINTER;  
   if ( 0 == cb )   
      return S_OK;   
  
   // Cut out now if threshold is hit.  
   __int64 left = m_i64ThreshHold-m_i64BytesUploaded;  
   if (left < cb)  
      cb = (ULONG)left;  
  
   if (0 == m_dwStartTick)  
      m_dwStartTick = GetTickCount();  
  
   m_i64BytesUploaded += cb;  
  
   if (( m_i64BytesUploaded - m_i64LastPrintUploaded ) >= (1024*1024*4)) {  
      __int64 i64Elapsed = (__int64) GetTickCount()-m_dwStartTick;  
      __int64 i64BytesPerSecond = m_i64BytesUploaded*1000/i64Elapsed;  
      printf("Param=%lu TotalBytes=%010I64u ElapsedMS=%010I64u BytesPerSec=%010I64u\n",   
         m_dwParamOrdinal, m_i64BytesUploaded, i64Elapsed, i64BytesPerSecond );  
      m_i64LastPrintUploaded = m_i64BytesUploaded;  
   }  
  
   if ( cb == left ) {  
      __int64 i64Elapsed = (__int64) GetTickCount()-m_dwStartTick;  
      __int64 i64BytesPerSecond = ( ( (m_i64BytesUploaded * 1000) / i64Elapsed) > 0 )  ? i64Elapsed : 1;  
      // __int64 i64BytesPerSecond = m_i64BytesUploaded * 1000 / (i64Elapsed > 0 ) ? i64Elapsed : 1;  
      printf("Last read:\nParam=%lu TotalBytes=%010I64u ElapsedMS=%010I64u BytesPerSec=%010I64u\n",   
         m_dwParamOrdinal, m_i64BytesUploaded, i64Elapsed, i64BytesPerSecond );  
      m_i64LastPrintUploaded = m_i64BytesUploaded;  
   }  
  
   if (pcbRead)  
      *pcbRead = cb;  
  
   return S_OK;  
}  
  
HRESULT CISSHelper::Write( const void *pv, ULONG cb, ULONG* pcbWritten ) {  
   // Check parameters.  
   if ( !pv )   
      return STG_E_INVALIDPOINTER;  
   if ( pcbWritten )   
      *pcbWritten = 0;  
   if ( 0 == cb )   
      return S_OK;  
  
   // Enlarge the current buffer.  
   m_ulLength += cb;  
  
   // Grow internal buffer to new size.  
   m_pBuffer = CoTaskMemRealloc( m_pBuffer, m_ulLength );  
  
   // Check for out of memory situation.  
   if ( NULL == m_pBuffer ) {  
      Clear();  
      return E_OUTOFMEMORY;  
   }  
  
   // Copy callers memory to internal buffer and update write position.  
   memcpy( (void*)((BYTE*)m_pBuffer + m_iWritePos), pv, cb );  
   m_iWritePos += cb;  
  
   // Return bytes written to caller.  
   if ( pcbWritten )   
      *pcbWritten = cb;  
  
   return S_OK;  
}

//  IBCPSession.cpp  
#pragma once  
#define WIN32_LEAN_AND_MEAN// Exclude rarely-used stuff from Windows headers  
#include <stdio.h>  
#include <conio.h>  
#include <tchar.h>  
#include <msoledbsql.h>  
  
#define SAFE_RELEASE(x)    { if (x) { x->Release(); x = NULL; } }  
#define SAFE_SYSFREE(bstr) { if (bstr) { ::SysFreeString(bstr); bstr = NULL; } }  
#define CHECK_HR(hr,jump)  { if ( FAILED(hr) ) goto jump; }  
#define CHECK_HR_ERR(hr,jump)  { if ( FAILED(hr) ) { DumpErrorRecords(); goto jump; } }  
  
// Helper function for DumpErrorRecords() to convert a clisd to string representation of clsid.  
LPWSTR CLSIDToString( CLSID* pclsid ) {  
   static WCHAR wszCLSID[1024];  
   if ( NULL == pclsid )  
      wcscpy_s(wszCLSID, 1024, L"(Null)");     
   else  
      ::StringFromGUID2( *pclsid, (OLECHAR*)wszCLSID, sizeof(wszCLSID) );  
   return wszCLSID;  
}  
  
// Helper function to dump out OLE DB errors to console window.  
HRESULT DumpErrorRecords() {  
   HRESULT hr = S_OK;  
   IErrorRecords* pIErrorRecords = NULL;  
   IErrorInfo* pIErrorInfo = NULL;  
   IErrorInfo* pIErrorInfoRecord = NULL;  
   BSTR bstrDescription = NULL;  
   BSTR bstrSource = NULL;  
   ULONG i;  
   ULONG cRecords = 0;  
   LCID lcid = 0;  
   ERRORINFO ErrorInfo;  
  
   // Get IErrorInfo pointer from OLE.  
   hr = ::GetErrorInfo( 0, &pIErrorInfo );  
   if ( FAILED(hr) ) {  
      printf( "No error records found.\n" );  
      goto DumpErrorRecordsExit;  
   }  
  
   // QI for IID_IErrorRecords.  
   hr = pIErrorInfo->QueryInterface( IID_IErrorRecords, (void**)&pIErrorRecords );  
   if ( FAILED(hr) ) {  
      printf( "pIErrorInfo->QueryInterface(IID_IErrorRecords) failed with hr=0x%08x.\n", hr );  
      goto DumpErrorRecordsExit;  
   }  
  
   // Get error record count.  
   hr = pIErrorRecords->GetRecordCount( &cRecords );  
   if ( FAILED(hr) ) {  
      printf( "pIErrorRecords->GetRecordCount() failed with hr=0x%08x.\n", hr );  
      goto DumpErrorRecordsExit;  
   }  
  
   // Get system LCID  
   lcid = GetSystemDefaultLCID();   
  
   // Loop through the error records.  
   for ( i = 0 ; i < cRecords ; i++ ) {  
      // Get pIErrorInfo from pIErrorRecords.  
      hr = pIErrorRecords->GetErrorInfo( i, lcid, &pIErrorInfoRecord );  
  
      if ( SUCCEEDED(hr) ) {  
         // Get error description and source.  
         hr = pIErrorInfoRecord->GetDescription( &bstrDescription );  
         hr = pIErrorInfoRecord->GetSource( &bstrSource );  
  
         // Retrieve the ErrorInfo structures.  
         hr = pIErrorRecords->GetBasicErrorInfo( i, &ErrorInfo );  
  
         // Dump out error.  
         printf( "\n" );  
         printf( "Dumping error record %lu of %lu:\n", i+1, cRecords );  
         printf( "--------------------------------------------------------------------------\n" );  
         printf( "   Description = %S\n", bstrDescription );  
         printf( "   Source      = %S\n", bstrSource );  
         printf( "   ERRORINFO.hrError = 0x%08x\n", ErrorInfo.hrError );  
         printf( "   ERRORINFO.dwMinor = %lu\n",ErrorInfo.dwMinor );   
         printf( "   ERRORINFO.clsid   = %S\n",CLSIDToString( &ErrorInfo.clsid ) );  
  
         SAFE_RELEASE(pIErrorInfoRecord);  
         SAFE_SYSFREE(bstrDescription);  
         SAFE_SYSFREE(bstrSource);  
      }  
   }  
  
DumpErrorRecordsExit:  
   SAFE_RELEASE(pIErrorInfoRecord);  
   SAFE_RELEASE(pIErrorRecords);  
   SAFE_RELEASE(pIErrorInfo);  
   SAFE_RELEASE(pIErrorInfo);  
   SAFE_SYSFREE(bstrDescription);  
   SAFE_SYSFREE(bstrSource);  
   return hr;  
}  
  
// to open a session  
  
// 1) create a properties object  
// 2) set properties on it (such as INIT_DATASOURCE, etc.)  
// 3) queryinterface an IDBInitialize on the properties object  
// 4) call IDBInitialize::Initialize  
// 5) queryinterface an IDBCreateSession on the IDBInitialize instance  
// 6) call IDBCreateSession::CreateSession with interface to use on the session (IDBCreateCommand, IOpenRowset, IBCPSession, etc.)  
  
HRESULT OpenSession( wchar_t* datasource, wchar_t* catalog, const IID& iid, void** out ) {  
#define SET_BSTR_PROP(index, proparray, propid, value) \  
   { proparray[index].dwOptions = DBPROPOPTIONS_REQUIRED; \  
   proparray[index].colid = DB_NULLID; \  
   proparray[index].dwStatus = DBPROPSTATUS_OK; \  
   proparray[index].dwPropertyID = propid; \  
   proparray[index].vValue.vt = VT_BSTR; \  
   proparray[index].vValue.bstrVal = SysAllocString(value); }  
  
#define SET_BOOL_PROP(index, proparray, propid, value) \  
   { proparray[index].dwOptions = DBPROPOPTIONS_REQUIRED; \  
   proparray[index].colid = DB_NULLID; \  
   proparray[index].dwStatus = DBPROPSTATUS_OK; \  
   proparray[index].dwPropertyID = propid; \  
   proparray[index].vValue.vt = VT_BOOL; \  
   proparray[index].vValue.boolVal = (value) ? VARIANT_TRUE : VARIANT_FALSE; }  
  
   HRESULT hr;  
  
   IDBProperties*     pIDBProperties = NULL;  
   IDBProperties*     pIDBSessionProperties = NULL;  
   IDBInitialize*     pIDBInitialize = NULL;    
   IDBCreateSession*  pIDBCreateSession = NULL;  
  
   DBPROP      InitProperties[3];  
   DBPROP      BulkCopyProperties[2];  
   DBPROPSET   PropSet[2];  
  
   hr = CoCreateInstance( MSOLEDBSQL_CLSID, NULL, CLSCTX_INPROC_SERVER, IID_IDBProperties,   
      (void **) &pIDBProperties );      
   CHECK_HR(hr,OpenSessionCleanup);  
  
   // Hard coded this to point to local sql server, change as needed.  
   SET_BSTR_PROP( 0, InitProperties, DBPROP_INIT_DATASOURCE, datasource );  
   SET_BSTR_PROP( 1, InitProperties, DBPROP_INIT_CATALOG, catalog );  
   SET_BSTR_PROP( 2, InitProperties, DBPROP_AUTH_INTEGRATED, L"SSPI" );  
  
   SET_BOOL_PROP( 0, BulkCopyProperties, SSPROP_ENABLEFASTLOAD, true );  
   SET_BOOL_PROP( 1, BulkCopyProperties, SSPROP_ENABLEBULKCOPY, true );  
  
   PropSet[0].guidPropertySet = DBPROPSET_DBINIT;   
   PropSet[0].cProperties = 3;                 
   PropSet[0].rgProperties = InitProperties;   
  
   PropSet[1].guidPropertySet = DBPROPSET_SQLSERVERDATASOURCE;  
   PropSet[1].cProperties = 2;  
   PropSet[1].rgProperties = BulkCopyProperties;  
  
   pIDBProperties->SetProperties( 1, (DBPROPSET*) &PropSet );  
   CHECK_HR( hr, OpenSessionCleanup );  
  
   hr = pIDBProperties->QueryInterface( IID_IDBInitialize, (void**) &pIDBInitialize );  
   CHECK_HR( hr,OpenSessionCleanup );  
  
   hr = pIDBInitialize->Initialize();  
   CHECK_HR( hr,OpenSessionCleanup );  
  
   // QI for IID_IDBCreateSession and then create session.  
   hr = pIDBInitialize->QueryInterface( IID_IDBCreateSession, (void**) &pIDBCreateSession );  
   CHECK_HR( hr,OpenSessionCleanup );  
  
   pIDBCreateSession->QueryInterface( IID_IDBProperties, (void**) &pIDBSessionProperties );  
   pIDBSessionProperties->SetProperties( 1, &PropSet[1] );  
  
   hr = pIDBCreateSession->CreateSession( NULL, iid, (IUnknown**) out );  
  
OpenSessionCleanup:  
   SAFE_RELEASE( pIDBProperties );  
   SAFE_RELEASE( pIDBInitialize );  
   SAFE_RELEASE( pIDBCreateSession );  
   SAFE_RELEASE( pIDBSessionProperties );  
   return hr;      
}  
  
int wmain(int argc, wchar_t* argv[]) {  
   HRESULT hr;  
   IBCPSession * pIBCPSession = NULL;  
   DBROWCOUNT rows;  
  
   CoInitialize(NULL);  
  
   if ( argc < 2 ) {  
      printf( "Usage: IBCPSession <server> <file> [<error file>]\n");  
      return 0;  
   }  
  
   // Open connection to database.  
   hr = OpenSession( argv[1], L"master", IID_IBCPSession, (void**) &pIBCPSession );  
   CHECK_HR_ERR(hr,MainCleanup);  
  
   // change the last parameter to BCP_DIRECTION_IN to make it write a file into the server  
   hr = pIBCPSession->BCPInit( L"[DBFsa]..[FSTRTable]", argv[2], (argc > 3) ? argv[3] : NULL, BCP_DIRECTION_OUT );  
   CHECK_HR_ERR( hr, MainCleanup );  
  
#define WRITE_FMT_FILE 1  
#if WRITE_FMT_FILE  
  
   hr = pIBCPSession->BCPColumns( 3 );  
   CHECK_HR_ERR( hr, MainCleanup );  
  
   hr = pIBCPSession->BCPColFmt( 1, BCP_TYPE_DEFAULT, BCP_PREFIX_DEFAULT, BCP_LENGTH_VARIABLE, NULL, 0, 1 );  
   CHECK_HR_ERR( hr, MainCleanup );  
  
   hr = pIBCPSession->BCPColFmt( 2, BCP_TYPE_DEFAULT, BCP_PREFIX_DEFAULT, BCP_LENGTH_VARIABLE, NULL, 0, 2 );  
   CHECK_HR_ERR( hr, MainCleanup );  
  
   hr = pIBCPSession->BCPColFmt( 3, BCP_TYPE_DEFAULT, BCP_PREFIX_DEFAULT, BCP_LENGTH_VARIABLE, NULL, 0, 3 );  
   CHECK_HR_ERR( hr, MainCleanup );  
  
   hr = pIBCPSession->BCPWriteFmt( L"fstrtable.fmt" );  
   CHECK_HR_ERR( hr, MainCleanup );  
  
#else  
  
   hr = pIBCPSession->BCPReadFmt( L"fstrtable.fmt" );  
   CHECK_HR_ERR( hr, MainCleanup );  
  
#endif  
  
   hr = pIBCPSession->BCPExec( &rows );  
   CHECK_HR_ERR( hr, MainCleanup );  
  
   hr = pIBCPSession->BCPDone();  
   CHECK_HR_ERR( hr, MainCleanup );  
  
MainCleanup:  
   SAFE_RELEASE( pIBCPSession );  
  
   printf_s( "Test complete.\n" );  
}

Dela via

Read a FILESTREAM Column to File Using IBCPSession (OLE DB)

Example

Feedback

Ytterligare resurser