Definir dados grandes (OLE DB)
Aplica-se a: 
SQL Server Banco de Dados SQL do Azure Instância Gerenciada de SQL do Azure Azure Synapse Analytics Analytics Platform System (PDW)
Este exemplo mostra como definir dados de BLOB, criar uma tabela, adicionar um registro de exemplo, buscar esse registro no conjunto de linhas e definir o valor do campo BLOB. Este exemplo não tem suporte em IA64.
Para transmitir um ponteiro para seu próprio objeto de armazenamento, o consumidor cria um acessador que associa o valor da coluna BLOB e chama os métodos IRowsetChange::SetData ou IRowsetChange::InsertRow.
Os exemplos de código do Transact-SQL deste artigo usa o banco de dados de exemplo AdventureWorks2022 ou AdventureWorksDW2022, que pode ser baixado da home page Microsoft SQL Server Samples and Community Projects.
Importante
Quando possível, use a Autenticação do Windows. Se a Autenticação do Windows não estiver disponível, solicite aos usuários que digitem suas credenciais em tempo de execução. Evite armazenar as credenciais em um arquivo. Se for necessário manter as credenciais, criptografe-as com a Win32 crypto API(em inglês).
Procedimentos
Para definir dados de BLOB
Crie uma estrutura DBOBJECT que descreva como a coluna BLOB deve ser acessada. Defina o elemento dwFlag da estrutura DBOBJECT como STGM_READ e defina o elemento iid como IID_ISequentialStream (a interface a ser exposta).
Defina as propriedades no grupo de propriedades DBPROPSET_ROWSET para que o conjunto de linhas seja atualizável.
Crie um conjunto de associações (uma de cada coluna) usando uma matriz de estruturas DBBINDING. Defina o elemento wType na estrutura DBBINDING como DBTYPE_IUNKNOWN e o elemento pObject para que ele aponte para a estrutura DBOBJECT criada.
Crie um acessador que usa as informações de associação na matriz de estruturas DBBINDINGS.
Chame GetNextRows para buscar as linhas seguintes no conjunto de linhas. Chame GetData para ler os dados do conjunto de linhas.
Para definir os dados, crie um objeto de armazenamento contendo os dados (e também o indicador de comprimento) e chame IRowsetChange::SetData (ou IRowsetChange::InsertRow) com o acessador que associa a coluna BLOB.
Exemplo
DESCRIÇÃO
Compile com ole32.lib oleaut32.lib e execute a seguinte listagem de código C++. Esse aplicativo se conecta à instância padrão do SQL Server do computador. Em alguns sistemas operacionais Windows, será necessário alterar (localhost) ou (local) para o nome de sua instância do SQL Server . Para se conectar a uma instância nomeada, altere a cadeia de conexão de L "(local)" para L"(local)\\name", em que name é a instância nomeada. Por padrão, o SQL Server Express é instalado em uma instância nomeada. Verifique se a variável de ambiente INCLUDE inclui o diretório que contém msoledbsql.h.
Código
// compile with: ole32.lib oleaut32.lib
#define UNICODE
#define DBINITCONSTANTS
#define INITGID
#define OLEDBVER 0x0250 // to include correct interfaces
#include <windows.h>
#include <stdio.h>
#include <stddef.h>
#include <iostream>
#include <oledb.h>
#include <oledberr.h>
#include <msoledbsql.h>
using namespace std;
#define SAFE_RELEASE(pIUnknown) if(pIUnknown) (pIUnknown)->Release();
HRESULT GetCommandObject(REFIID riid, IUnknown** ppIUnknown);
HRESULT CreateTable(ICommandText* pICommandText);
class CSeqStream : public ISequentialStream {
public:
// Constructors
CSeqStream();
virtual ~CSeqStream();
virtual BOOL Seek(ULONG iPos);
virtual BOOL Clear();
virtual BOOL CompareData(void* pBuffer);
virtual ULONG Length() { return m_cBufSize; };
virtual operator void* const() { return m_pBuffer; };
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);
private:
ULONG m_cRef; // reference count
void* m_pBuffer; // buffer
ULONG m_cBufSize; // buffer size
ULONG m_iPos; // current index position in the buffer
};
// class implementation
CSeqStream::CSeqStream() {
m_iPos = 0;
m_cRef = 0;
m_pBuffer = NULL;
m_cBufSize = 0;
// The constructor AddRef's
AddRef();
}
CSeqStream::~CSeqStream() {
// Shouldn't have any references left ASSERT(m_cRef == 0);
CoTaskMemFree(m_pBuffer);
}
ULONG CSeqStream::AddRef() {
return ++m_cRef;
}
ULONG CSeqStream::Release() {
// ASSERT(m_cRef);
if (--m_cRef)
return m_cRef;
delete this;
return 0;
}
HRESULT CSeqStream::QueryInterface(REFIID riid, void** ppv) {
// ASSERT(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;
}
BOOL CSeqStream::Seek(ULONG iPos) {
// Make sure the desired position is within the buffer
// ASSERT(iPos == 0 || iPos < m_cBufSize);
// Reset the current buffer position
m_iPos = iPos;
return TRUE;
}
BOOL CSeqStream::Clear() {
// Frees the buffer
m_iPos = 0;
m_cBufSize = 0;
CoTaskMemFree(m_pBuffer);
m_pBuffer = NULL;
return TRUE;
}
BOOL CSeqStream::CompareData(void* pBuffer) {
// ASSERT(pBuffer);
// Quick and easy way to compare user buffer with the stream
return memcmp(pBuffer, m_pBuffer, m_cBufSize) == 0;
}
HRESULT CSeqStream::Read(void *pv, ULONG cb, ULONG* pcbRead) {
// Parameter checking
if (pcbRead)
*pcbRead = 0;
if (!pv)
return STG_E_INVALIDPOINTER;
if (cb == 0)
return S_OK;
// Actual code
ULONG cBytesLeft = m_cBufSize - m_iPos;
ULONG cBytesRead = cb > cBytesLeft ? cBytesLeft : cb;
// if no more bytes to retrieve return
if (cBytesLeft == 0)
return S_FALSE;
// Copy to users buffer the number of bytes requested or remaining
memcpy(pv, (void*)((BYTE*)m_pBuffer + m_iPos), cBytesRead);
m_iPos += cBytesRead;
if (pcbRead)
*pcbRead = cBytesRead;
if (cb != cBytesRead)
return S_FALSE;
return S_OK;
}
HRESULT CSeqStream::Write(const void *pv, ULONG cb, ULONG* pcbWritten) {
// Parameter checking
if (!pv)
return STG_E_INVALIDPOINTER;
if (pcbWritten)
*pcbWritten = 0;
if (cb == 0)
return S_OK;
// Enlarge the current buffer
m_cBufSize += cb;
// Need to append to the end of the stream
m_pBuffer = CoTaskMemRealloc(m_pBuffer, m_cBufSize);
memcpy((void*)((BYTE*)m_pBuffer + m_iPos), pv, cb);
// m_iPos += cb;
if (pcbWritten)
*pcbWritten = cb;
return S_OK;
}
int main() {
CoInitialize(NULL);
DBOBJECT ObjectStruct;
ObjectStruct.dwFlags = STGM_READ;
ObjectStruct.iid = IID_ISequentialStream;
struct BLOBDATA {
DBSTATUS dwStatus;
DBLENGTH dwLength;
ISequentialStream* pISeqStream;
};
BLOBDATA BLOBGetData;
BLOBDATA BLOBSetData;
const ULONG cBindings = 1;
DBBINDING rgBindings[cBindings];
HRESULT hr = S_OK;
IAccessor* pIAccessor = NULL;
ICommandText* pICommandText = NULL;
ICommandProperties* pICommandProperties = NULL;
IRowsetChange* pIRowsetChange = NULL;
IRowset* pIRowset = NULL;
CSeqStream* pMySeqStream = NULL;
DBCOUNTITEM cRowsObtained = 0;
HACCESSOR hAccessor = DB_NULL_HACCESSOR;
DBBINDSTATUS rgBindStatus[cBindings];
HROW* rghRows = NULL;
const ULONG cPropSets = 1;
DBPROPSET rgPropSets[cPropSets];
const ULONG cProperties = 1;
DBPROP rgProperties[cProperties];
const ULONG cBytes = 10;
BYTE pBuffer[cBytes];
ULONG cBytesRead = 0;
BYTE pReadData[cBytes]; // read BLOB data in this array
memset(pReadData, 0xAA, cBytes);
BYTE pWriteData[cBytes]; // write BLOB data from this array
memset(pWriteData, 'D', cBytes);
// Get Command object
hr = GetCommandObject(IID_ICommandText, (IUnknown**)&pICommandText);
if (FAILED(hr)) {
printf("Failed to get ICommandText interface.\n");
// Release any references and return.
goto Exit;
}
// Create table with image column and index
hr = CreateTable(pICommandText);
if (FAILED(hr)) {
printf("Failed to create table.\n");
// Release any references and return.
goto Exit;
}
// Set the DBPROPSET structure. It is used to pass an array
// of DBPROP structures to SetProperties().
rgPropSets[0].guidPropertySet = DBPROPSET_ROWSET;
rgPropSets[0].cProperties = cProperties;
rgPropSets[0].rgProperties = rgProperties;
// Now set properties in the property group (DBPROPSET_ROWSET)
rgPropSets[0].rgProperties[0].dwPropertyID = DBPROP_UPDATABILITY;
rgPropSets[0].rgProperties[0].dwOptions = DBPROPOPTIONS_REQUIRED;
rgPropSets[0].rgProperties[0].dwStatus = DBPROPSTATUS_OK;
rgPropSets[0].rgProperties[0].colid = DB_NULLID;
rgPropSets[0].rgProperties[0].vValue.vt = VT_I4;
V_I4(&rgPropSets[0].rgProperties[0].vValue) = DBPROPVAL_UP_CHANGE;
// Set the rowset properties
hr = pICommandText->QueryInterface(IID_ICommandProperties,
(void **)&pICommandProperties);
if (FAILED(hr)) {
printf("Failed to get ICommandProperties to set rowset properties.\n");
// Release any references and return.
goto Exit;
}
hr = pICommandProperties->SetProperties(cPropSets, rgPropSets);
if (FAILED(hr)) {
printf("Execute failed to set rowset properties.\n");
// Release any references and return.
goto Exit;
}
// Execute a command (SELECT * FROM TestISeqStream)
hr = pICommandText->SetCommandText(DBGUID_DBSQL, L"SELECT * FROM TestISeqStream");
if (FAILED(hr)) {
printf("Failed to set command text SELECT * FROM.\n");
// Release any references and return.
goto Exit;
}
hr = pICommandText->Execute(NULL,
IID_IRowsetChange,
NULL,
NULL,
(IUnknown**)&pIRowsetChange);
if (FAILED(hr)) {
printf("Failed to execute the command SELECT * FROM.\n");
// Release any references and return.
goto Exit;
}
// Fill the DBBINDINGS array.
rgBindings[0].iOrdinal = 2; // ordinal position
rgBindings[0].obValue = offsetof(BLOBDATA, pISeqStream);
rgBindings[0].obLength = offsetof(BLOBDATA, dwLength);
rgBindings[0].obStatus = offsetof(BLOBDATA, dwStatus);
rgBindings[0].pTypeInfo = NULL;
rgBindings[0].pObject = &ObjectStruct;
rgBindings[0].pBindExt = NULL;
rgBindings[0].dwPart = DBPART_VALUE | DBPART_STATUS | DBPART_LENGTH;
rgBindings[0].dwMemOwner = DBMEMOWNER_CLIENTOWNED;
rgBindings[0].eParamIO = DBPARAMIO_NOTPARAM;
rgBindings[0].cbMaxLen = 0;
rgBindings[0].dwFlags = 0;
rgBindings[0].wType = DBTYPE_IUNKNOWN;
rgBindings[0].bPrecision = 0;
rgBindings[0].bScale = 0;
// Create an accessor using the binding information.
hr = pIRowsetChange->QueryInterface(IID_IAccessor, (void**)&pIAccessor);
if (FAILED(hr)) {
printf("Failed to get IAccessor interface.\n");
// Release any references and return.
goto Exit;
}
hr = pIAccessor->CreateAccessor(DBACCESSOR_ROWDATA,
cBindings,
rgBindings,
sizeof(BLOBDATA),
&hAccessor,
rgBindStatus);
if (FAILED(hr)) {
printf("Failed to create an accessor.\n");
// Release any references and return.
goto Exit;
}
// get the first row.
hr = pIRowsetChange->QueryInterface(IID_IRowset, (void **)&pIRowset);
if (FAILED(hr)) {
printf("Failed to get IRowset interface.\n");
// Release any references and return.
goto Exit;
}
hr = pIRowset->GetNextRows(NULL, 0, 1, &cRowsObtained, &rghRows);
hr = pIRowset->GetData(rghRows[0], hAccessor, &BLOBGetData);
// Verify the retrieved data, only if data is not null.
if (BLOBGetData.dwStatus == DBSTATUS_S_ISNULL) {
// Process null data
printf("Provider returned a null value.\n");
}
else if(BLOBGetData.dwStatus == DBSTATUS_S_OK) {
// Provider returned a nonNULL value
BLOBGetData.pISeqStream->Read( pBuffer, cBytes, &cBytesRead);
if (memcmp(pBuffer, pReadData, cBytes) != 0) {
// cleanup
}
SAFE_RELEASE(BLOBGetData.pISeqStream);
}
// Set up data for SetData.
pMySeqStream = new CSeqStream();
// Put data into ISequentialStream object for the provider to write.
pMySeqStream->Write(pWriteData, cBytes, NULL);
BLOBSetData.pISeqStream = (ISequentialStream*)pMySeqStream;
BLOBSetData.dwStatus = DBSTATUS_S_OK;
BLOBSetData.dwLength = pMySeqStream->Length();
// Set the data.
hr = pIRowsetChange->SetData(rghRows[0], hAccessor, &BLOBSetData);
if (FAILED(hr)) {
printf("Failed to set data.\n");
// Release any references and return.
goto Exit;
}
hr = pIAccessor->ReleaseAccessor(hAccessor, NULL);
if (FAILED(hr)) {
printf("Failed to release accessor.\n");
// Release any references and return.
goto Exit;
}
hr = pIRowset->ReleaseRows(cRowsObtained, rghRows, NULL, NULL, NULL);
if (FAILED(hr)) {
printf("Failed to release rows.\n");
// Release any references and return.
goto Exit;
}
Exit:
// Release all allocated memory and release interface pointers.
CoUninitialize();
}
HRESULT GetCommandObject(REFIID riid, IUnknown** ppIUnknown) {
HRESULT hr = S_OK;
// Local interface pointers, until a connection is made.
IDBInitialize* pIDBInitialize = NULL;
IDBProperties* pIDBProperties = NULL;
IDBCreateSession* pIDBCreateSession = NULL;
IDBCreateCommand* pIDBCreateCommand = NULL;
const ULONG cPropSets = 1;
DBPROPSET rgPropSets[cPropSets];
const ULONG cProperties = 4;
DBPROP rgProperties[cProperties];
// Initialize property values needed to establish connection.
for ( ULONG i = 0 ; i < 4 ; i++ )
VariantInit(&rgProperties[i].vValue);
// Server name.
rgProperties[0].dwPropertyID = DBPROP_INIT_DATASOURCE;
rgProperties[0].vValue.vt = VT_BSTR;
rgProperties[0].vValue.bstrVal = SysAllocString(L"(local)");
rgProperties[0].dwOptions = DBPROPOPTIONS_REQUIRED;
rgProperties[0].colid = DB_NULLID;
// Database.
rgProperties[1].dwPropertyID = DBPROP_INIT_CATALOG;
rgProperties[1].vValue.vt = VT_BSTR;
rgProperties[1].vValue.bstrVal = SysAllocString(L"AdventureWorks");
rgProperties[1].dwOptions = DBPROPOPTIONS_REQUIRED;
rgProperties[1].colid = DB_NULLID;
rgProperties[2].dwPropertyID = DBPROP_AUTH_INTEGRATED;
rgProperties[2].vValue.vt = VT_BSTR;
rgProperties[2].vValue.bstrVal = SysAllocString(L"SSPI");
rgProperties[2].dwOptions = DBPROPOPTIONS_REQUIRED;
rgProperties[2].colid = DB_NULLID;
// Properties are now set. Next, construct DBPROPSET structure (rgInitPropSet) used to pass an
// array of DBPROP structures (InitProperties) to the SetProperties method.
rgPropSets[0].guidPropertySet = DBPROPSET_DBINIT;
rgPropSets[0].cProperties = cProperties;
rgPropSets[0].rgProperties = rgProperties;
// Get the IDBInitialize interface.
hr = CoCreateInstance(CLSID_MSOLEDBSQL,
NULL,
CLSCTX_INPROC_SERVER,
IID_IDBInitialize,
(void**)&pIDBInitialize);
if (FAILED(hr)) {
printf("Failed to get IDBInitialize interface.\n");
// Release any references and return.
goto Exit;
}
// Set initialization properties.
hr = pIDBInitialize->QueryInterface(IID_IDBProperties, (void **)&pIDBProperties);
if (FAILED(hr)) {
printf("Failed to get IDBProperties interface.\n");
// Release any references and return.
goto Exit;
}
hr = pIDBProperties->SetProperties(cPropSets, rgPropSets);
if (FAILED(hr)) {
printf("Failed to set properties for DBPROPSET_DBINIT.\n");
// Release any references and return.
goto Exit;
}
hr = pIDBInitialize->Initialize();
if (FAILED(hr)) {
printf("Failed to initialize.\n");
// Release any references and return.
goto Exit;
}
// Create a session object.
hr = pIDBInitialize->QueryInterface( IID_IDBCreateSession,
(void **)&pIDBCreateSession);
if (FAILED(hr)) {
printf("Failed to get pIDBCreateSession interface.\n");
// Release any references and return.
goto Exit;
}
hr = pIDBCreateSession->CreateSession( NULL, IID_IDBCreateCommand, (IUnknown**)&pIDBCreateCommand);
if (FAILED(hr)) {
printf("Failed to create session object.\n");
// Release any references and return.
goto Exit;
}
// Get CommandText object
hr = pIDBCreateCommand->CreateCommand( NULL, riid, (IUnknown**)ppIUnknown);
if (FAILED(hr)) {
printf("Failed to create CommandText object.\n");
// Release any references and return.
goto Exit;
}
return hr;
Exit:
// Free up all allocated memory and release interface pointers.
return hr;
}
HRESULT CreateTable(ICommandText* pICommandText) {
HRESULT hr = S_OK;
// drop the table "TestISeqStream" if the table exists.
hr = pICommandText->SetCommandText( DBGUID_DBSQL, L"if object_id('TestISeqStream') is not null drop table TestISeqStream");
if (FAILED(hr)) {
printf("Failed to set command text DROP TABLE.\n");
// Release any references and return.
goto Exit;
}
hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);
if (FAILED(hr)) {
printf("Failed to drop the table.\n");
// Release any references and return.
goto Exit;
}
// Create a new table.
hr = pICommandText->SetCommandText(DBGUID_DBSQL,
L"CREATE TABLE TestISeqStream (col1 int,col2 image)");
if (FAILED(hr)) {
printf("Failed to set command text CREATE TABLE.\n");
// Release any references and return.
goto Exit;
}
hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);
if (FAILED(hr)) {
printf("Failed to create table.\n");
// Release any references and return.
goto Exit;
}
// Insert one row into table.
hr = pICommandText->SetCommandText(DBGUID_DBSQL,
L"INSERT INTO TestISeqStream(col1,col2) VALUES (1,0xAAAAAAAAAAAAAAAAA)");
if (FAILED(hr)) {
printf("Failed to set command text INSERT INTO.\n");
// Release any references and return.
goto Exit;
}
hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);
if (FAILED(hr)) {
printf("Failed to insert record in the table.\n");
// Release any references and return.
goto Exit;
}
Exit:
// Release all allocated memory and release interface pointers.
return hr;
}