设置大型数据
适用于：
SQL ServerAzure SQL 数据库Azure SQL 托管实例Azure Synapse AnalyticsAnalytics Platform System (PDW)
借助于 OLE DB Driver for SQL Server，你可以通过将指针传递给使用者存储对象来设置 BLOB 数据。
使用者创建包含数据的存储对象，并将指向此存储对象的指针传递给访问接口。 然后，访问接口从使用者存储对象读取数据，并将其写入 BLOB 列中。
为了将指针传递给它自己的存储对象，使用者创建一个取值函数，该取值函数绑定 BLOB 列的值。 然后，使用者通过绑定 BLOB 列的取值函数调用 IRowsetChange::SetData 或 IRowsetChange::InsertRow 方法 。 它将指针传递给使用者的存储对象中的某个存储接口。
本主题涉及可用于以下函数的功能：
IRowset:SetData
ICommand::Execute
IRowsetUpdate::Update
如何设置大型数据
为了将指针传递给它自己的存储对象，使用者创建一个绑定 BLOB 列的值的取值函数，然后调用 IRowsetChange::SetData 或 IRowsetChange::InsertRow 方法 。 若要设置 BLOB 数据，请：
创建一个描述应如何访问 BLOB 列的 DBOBJECT 结构。 将 DBOBJECT 结构的 dwFlag 元素设置为 STGM_READ，并将 iid 元素设置为 IID_ISequentialStream（要公开的接口） 。
设置 DBPROPSET_ROWSET 属性组中的属性，以使行集可更新。
通过使用 DBBINDING 结构数组创建一组绑定（每列一个）。 将 DBBINDING 结构中的 wType 元素设置为 DBTYPE_IUNKNOWN，并将 pObject 元素设置为指向创建的 DBOBJECT 结构 。
使用 DBBINDINGS 结构数组中的绑定信息创建取值函数。
调用 GetNextRows 将后续的行提取到行集中 。 调用 GetData 以读取行集中的数据 。
创建一个包含数据（及长度指示器）的存储对象，然后通过绑定 BLOB 列的取值函数调用 IRowsetChange::SetData（或 IRowsetChange::InsertRow）以设置数据 。
示例
本示例说明如何设置 BLOB 数据。 本示例创建表、添加示例记录、从行集中提取该记录，然后设置该 BLOB 字段的值：
#define UNICODE
#define DBINITCONSTANTS
#define INITGID
#include <windows.h>
#include <stdio.h>
#include <stddef.h>
#include <iostream.h>
#include <oledb.h>
#include <oledberr.h>
#include <msoledbsql.h>
#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);
protected:
//Data
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(void)
{
return ++m_cRef;
}
ULONG CSeqStream::Release(void)
{
// 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_s(pv, sizeof(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_s((void*)((BYTE*)m_pBuffer + m_iPos), sizeof((void*)((BYTE*)m_pBuffer + m_iPos)), pv, cb);
// m_iPos += cb;
if(pcbWritten)
*pcbWritten = cb;
return S_OK;
}
//...........................................................
void main()
{
CoInitialize(NULL);
DBOBJECT ObjectStruct;
ObjectStruct.dwFlags = STGM_READ;
ObjectStruct.iid = IID_ISequentialStream;
struct BLOBDATA
{
DBSTATUS dwStatus;
DWORD 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;
ULONG 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 the Command object.
hr = GetCommandObject(IID_ICommandText,
(IUnknown**)&pICommandText);
if (FAILED(hr))
{
cout << "Failed to get ICommandText interface.\n";
// Release any references and return.
goto Exit;
} //end if
// Create table with image column and index.
hr = CreateTable(pICommandText);
if (FAILED(hr))
{
cout << "Failed to create table.\n";
// Release any references and return.
goto Exit;
} //end if
/*
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))
{
cout << "Failed to get ICommandProperties to set rowset properties.\n";
// Release any references and return.
goto Exit;
} //end if
hr = pICommandProperties->SetProperties(cPropSets, rgPropSets);
if (FAILED(hr))
{
cout << "Execute failed to set rowset properties.\n";
// Release any references and return.
goto Exit;
} //end if
// Execute a command (SELECT * FROM TestISeqStream).
hr = pICommandText->SetCommandText(DBGUID_DBSQL,
L"SELECT * FROM TestISeqStream");
if (FAILED(hr))
{
cout << "Failed to set command text SELECT * FROM.\n";
// Release any references and return.
goto Exit;
} //end if
hr = pICommandText->Execute(NULL, IID_IRowsetChange, NULL, NULL,
(IUnknown**)&pIRowsetChange);
if (FAILED(hr))
{
cout << "Failed to execute the command SELECT * FROM.\n";
// Release any references and return.
goto Exit;
} //end if
// 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))
{
cout << "Failed to get IAccessor interface.\n";
// Release any references and return.
goto Exit;
} //end if
hr = pIAccessor->CreateAccessor(DBACCESSOR_ROWDATA,
cBindings,
rgBindings,
sizeof(BLOBDATA),
&hAccessor,
rgBindStatus);
if (FAILED(hr))
{
cout << "Failed to create an accessor.\n";
// Release any references and return.
goto Exit;
} //end if
// Now get the first row.
hr = pIRowsetChange->QueryInterface(IID_IRowset,
(void **)&pIRowset);
if (FAILED(hr))
{
cout << "Failed to get IRowset interface.\n";
// Release any references and return.
goto Exit;
} //end if
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.
cout << "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 in to the 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))
{
cout << "Failed to set data.\n";
// Release any references and return.
goto Exit;
} //end if
hr = pIAccessor->ReleaseAccessor(hAccessor, NULL);
if (FAILED(hr))
{
cout << "Failed to release accessor.\n";
// Release any references and return.
goto Exit;
} //end if
hr = pIRowset->ReleaseRows(cRowsObtained,
rghRows,
NULL,
NULL,
NULL);
if (FAILED(hr))
{
cout << "Failed to release rows.\n";
// Release any references and return.
goto Exit;
} //end if
Exit:
// Free up all allocated memory and release interface pointers.
CoUninitialize();
} //end main.
//..........................................................
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 the property values needed to
establish the 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"server");
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"pubs");
rgProperties[1].dwOptions = DBPROPOPTIONS_REQUIRED;
rgProperties[1].colid = DB_NULLID;
// Username (login).
rgProperties[2].dwPropertyID = DBPROP_AUTH_USERID;
rgProperties[2].vValue.vt = VT_BSTR;
rgProperties[2].vValue.bstrVal =
SysAllocString(L"login");
rgProperties[2].dwOptions = DBPROPOPTIONS_REQUIRED;
rgProperties[2].colid = DB_NULLID;
// Password.
rgProperties[3].dwPropertyID = DBPROP_AUTH_PASSWORD;
rgProperties[3].vValue.vt = VT_BSTR;
rgProperties[3].vValue.bstrVal =
SysAllocString(L"password");
rgProperties[3].dwOptions = DBPROPOPTIONS_REQUIRED;
rgProperties[3].colid = DB_NULLID;
/*
Now that the properties are set, construct the DBPROPSET
structure (rgInitPropSet). The DBPROPSET structure is 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))
{
cout << "Failed to get IDBInitialize interface.\n";
// Release any references and return.
goto Exit;
} //end if
// Set initialization properties.
hr = pIDBInitialize->QueryInterface(IID_IDBProperties,
(void **)&pIDBProperties);
if(FAILED(hr))
{
cout << "Failed to get IDBProperties interface.\n";
// Release any references and return.
goto Exit;
} //end if
hr = pIDBProperties->SetProperties(cPropSets, rgPropSets);
if(FAILED(hr))
{
cout << "Failed to set properties for DBPROPSET_DBINIT.\n";
// Release any references and return.
goto Exit;
} //end if
hr = pIDBInitialize->Initialize();
if(FAILED(hr))
{
cout << "Failed to initialize.\n";
// Release any references and return.
goto Exit;
} // end if
//Create a session object.
hr = pIDBInitialize->QueryInterface(
IID_IDBCreateSession,
(void **)&pIDBCreateSession);
if(FAILED(hr))
{
cout << "Failed to get pIDBCreateSession interface.\n";
// Release any references and return.
goto Exit;
} // end if
hr = pIDBCreateSession->CreateSession(
NULL,
IID_IDBCreateCommand,
(IUnknown**)&pIDBCreateCommand);
if(FAILED(hr))
{
cout << "Failed to create session object.\n";
// Release any references and return.
goto Exit;
} // end if
// Get the CommandText object.
hr = pIDBCreateCommand->CreateCommand(
NULL,
riid,
(IUnknown**)ppIUnknown);
if(FAILED(hr))
{
cout << "Failed to create CommandText object.\n";
// Release any references and return.
goto Exit;
} // end if
return hr;
Exit:
// Free up all allocated memory and release interface pointers.
return hr;
} //end function
//...............................................................
HRESULT CreateTable(ICommandText* pICommandText)
{
HRESULT hr = S_OK;
// Drop the xisting table.
hr = pICommandText->SetCommandText(
DBGUID_DBSQL,
L"DROP TABLE TestISeqStream");
if(FAILED(hr))
{
cout << "Failed to set command text DROP TABLE.\n";
// Release any references and return.
goto Exit;
} //end if
hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);
if(FAILED(hr))
{
cout << "Failed to drop the table.\n";
// Release any references and return.
goto Exit;
} // end if
// Create a new table.
hr = pICommandText->SetCommandText(DBGUID_DBSQL,
L"CREATE TABLE TestISeqStream (col1 int,col2 image)");
if(FAILED(hr))
{
cout << "Failed to set command text CREATE TABLE.\n";
// Release any references and return.
goto Exit;
} // end if
hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);
if(FAILED(hr))
{
cout << "Failed to create new table.\n";
// Release any references and return.
goto Exit;
} // end if
// Insert one row into table.
hr = pICommandText->SetCommandText(DBGUID_DBSQL,
L"INSERT INTO TestISeqStream(col1,col2) VALUES (1,0xAAAAAAAAAAAAAAAAA)");
if(FAILED(hr))
{
cout << "Failed to set command text INSERT INTO.\n";
// Release any references and return.
goto Exit;
} // end if
hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);
if(FAILED(hr))
{
cout << "Failed to insert record in the table.\n";
// Release any references and return.
goto Exit;
} // end if
Exit:
// Free up all allocated memory and release interface pointers.
return hr;
} //end function
另请参阅
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