大きなデータの設定
適用対象: 
SQL Server Azure SQL データベース Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW)
OLE DB Driver for SQL Server では、コンシューマー ストレージ オブジェクトへのポインターを渡すことにより、BLOB データを設定できます。
コンシューマーは、データを保持するストレージ オブジェクトを作成し、このストレージ オブジェクトへのポインターをプロバイダーに渡します。 次に、プロバイダーがコンシューマー ストレージ オブジェクトからデータを読み取り、BLOB 列に書き込みます。
コンシューマーは独自のストレージ オブジェクトへのポインターを渡すために、BLOB 列の値をバインドするアクセサーを作成します。 次に、BLOB 列をバインドするアクセサーを指定して、IRowsetChange::SetData メソッドまたは IRowsetChange::InsertRow メソッドを呼び出します。 このとき、コンシューマーのストレージ オブジェクトのストレージ インターフェイスへのポインターを渡します。
このトピックでは、次の関数で使用可能な機能について説明します。
IRowset:SetData
ICommand::Execute
IRowsetUpdate::Update
大きなデータを設定する方法
コンシューマーは、独自のストレージ オブジェクトへのポインターを渡すために、BLOB 列の値をバインドするアクセサーを作成します。次に、IRowsetChange::SetData メソッドまたは IRowsetChange::InsertRow メソッドを呼び出します。 BLOB データを設定するには、次の手順を実行します。
BLOB 列へのアクセス方法を説明する DBOBJECT 構造体を作成します。 DBOBJECT 構造体の dwFlag 要素に STGM_READ を設定し、iid 要素に IID_ISequentialStream (公開されるインターフェイス) を設定します。
行セットが更新可能になるように、DBPROPSET_ROWSET プロパティ グループのプロパティを設定します。
DBBINDING 構造体の配列を使用して、各列に 1 つずつ一連のバインドを作成します。 DBBINDING 構造体の wType 要素に DBTYPE_IUNKNOWN を設定し、pObject 要素に作成した DBOBJECT 構造体へのポインターを設定します。
DBBINDINGS 構造体の配列内のバインド情報を使用して、アクセサーを作成します。
GetNextRows を呼び出して、次の行を行セットにフェッチします。 GetData を呼び出して、その行セットからデータを読み取ります。
データ (および長さのインジケーター) を保持するストレージ オブジェクトを作成し、次に BLOB 列をバインドするアクセサーを指定して IRowsetChange::SetData (または IRowsetChange::InsertRow) を呼び出し、データを設定します。
例
次の例は、BLOB データを設定する方法を示しています。 この例では、テーブルを作成し、サンプル レコードを追加して、行セット内のそのレコードをフェッチし、BLOB フィールドの値を設定しています。
#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