SQL Server Native Client 中 BLOB 输出参数的流式处理支持
适用于：
SQL Server Azure SQL 数据库 Azure SQL 托管实例 Azure Synapse Analytics Analytics Platform System (PDW)
本主题包含一个示例，显示针对 BLOB 输出参数的流支持，它将 BLOB 输出参数绑定为 ISequentialStreams。
可以在 IMultipleResults::GetResult 中锁定输出参数，并且接收 DB_E_OBJECTOPEN 返回值。 调用方应检查是否存在挂起的 blob 参数，并且完全读取它们或释放它们。
示例
代码
// blob_out_param.cpp
// compile with: /EHsc ole32.lib oleaut32.lib
#define UNICODE
#define DBINITCONSTANTS
#define INITGUID
#define OLEDBVER 0x0250
#include <windows.h>
// Change the following to match your server and test database,
// and also the 'use' statement in the setup SQL that follows
const WCHAR* g_wchServerName = L".";
const WCHAR* g_wchDBName = L"TestDB";
const WCHAR* g_wchSecurity = L"SSPI";
/*
// Execute the following before running the program
use TestDB
go
drop proc Scenario1
go
drop table tScenario1
go
create table tScenario1 (c1 int, c2 varchar(20))
go
insert into tScenario1 values (1, 'abcdefgh')
insert into tScenario1 values (2, 'ijklm')
insert into tScenario1 values (3, 'nopqr')
insert into tScenario1 values (4, 'stuvwxyz')
go
create proc Scenario1 @p1 int output, @p2 varchar(max) output, @p3 xml output, @p4 varchar(20) output
as
begin
set @p1 = @p1 + 5
set @p2 = replicate(convert(varchar(max), 'a'), 10000)
set @p3 = '<tag1>Some text</tag1>'
set @p4 = '@p4 varchar(20)'
select * from tScenario1
return datalength(@p2)
end
go
------------------------- TESTING CODE -------------------------
declare @v1 int
set @v1 = 16
declare @v2 varchar(max)
declare @v3 xml
declare @v4 varchar(20)
declare @ret_val int
exec @ret_val = Scenario1 @v1 output, @v2 output, @v3 output, @v4 output
print @v1
print @v2
print convert(nchar, @v3)
print @v4
print @ret_val
go
*/
#include <stdio.h>
#include <stddef.h>
#include <iostream>
#include <oledb.h>
#include <oledberr.h>
#include <sqlncli.h>
#include <iostream>
#include <tchar.h>
using namespace std;
#define CHKHR_GOTO(hr, lblExit, szMsg) \
do \
{ \
if (FAILED(hr)) \
{ \
cout << szMsg << endl; \
goto lblExit; \
} \
} \
while (0)
#define RELEASE_ITF(pItf) \
if (pItf) \
{ \
pItf->Release(); \
pItf = NULL; \
}
#define INIT_BINDINGS(acDBBinding, nBindings) \
for(int uIndex = 0; uIndex < nBindings; uIndex++) { \
acDBBinding[uIndex].iOrdinal = uIndex + 1; \
acDBBinding[uIndex].obLength = 0; \
acDBBinding[uIndex].obStatus = 0; \
acDBBinding[uIndex].pTypeInfo = NULL; \
acDBBinding[uIndex].pObject = NULL; \
acDBBinding[uIndex].pBindExt = NULL; \
acDBBinding[uIndex].dwPart = DBPART_VALUE; \
acDBBinding[uIndex].dwMemOwner = DBMEMOWNER_CLIENTOWNED; \
acDBBinding[uIndex].dwFlags = 0; \
acDBBinding[uIndex].bScale = 0; \
}
IDBInitialize* pIDBInitialize = NULL;
HRESULT Connect(ICommandText** ppICommandText) {
HRESULT hr;
IDBProperties* pIDBProperties = NULL;
IDBCreateSession* pIDBCreateSession = NULL;
IDBCreateCommand* pIDBCreateCommand = NULL;
ICommandText* pICommandText = NULL;
const ULONG nInitProps = 3;
const ULONG nPropSet = 1;
DBPROP InitProperties[nInitProps];
DBPROPSET InitPropSet [nPropSet];
*ppICommandText = NULL;
hr = CoInitialize(NULL);
CHKHR_GOTO(hr, _ExitConnect, "Unable to Initialize COM.");
hr = CoCreateInstance(CLSID_SQLNCLI11, NULL, CLSCTX_INPROC_SERVER, IID_IDBInitialize, (void **) &pIDBInitialize);
CHKHR_GOTO(hr, _ExitConnect, "Unable to Load SQLNCLI11.");
for(ULONG uIndexProp = 0; uIndexProp < nInitProps; uIndexProp++) {
VariantInit(&InitProperties[uIndexProp].vValue);
InitProperties[uIndexProp].vValue.vt = VT_BSTR;
InitProperties[uIndexProp].dwOptions = DBPROPOPTIONS_REQUIRED;
InitProperties[uIndexProp].colid = DB_NULLID;
}
InitProperties[0].dwPropertyID = DBPROP_INIT_DATASOURCE;
InitProperties[0].vValue.bstrVal = SysAllocString(g_wchServerName);
InitProperties[1].dwPropertyID = DBPROP_INIT_CATALOG;
InitProperties[1].vValue.bstrVal = SysAllocString(g_wchDBName);
InitProperties[2].dwPropertyID = DBPROP_AUTH_INTEGRATED;
InitProperties[2].vValue.bstrVal = SysAllocString(g_wchSecurity);
InitPropSet[0].guidPropertySet = DBPROPSET_DBINIT;
InitPropSet[0].cProperties = 3;
InitPropSet[0].rgProperties = InitProperties;
hr = pIDBInitialize->QueryInterface(IID_IDBProperties, (void **)&pIDBProperties);
CHKHR_GOTO(hr, _ExitConnect, "Failed to obtain IDBProperties interface.");
hr = pIDBProperties->SetProperties(nPropSet, InitPropSet);
CHKHR_GOTO(hr, _ExitConnect, "Failed to Set Initialization properties.");
hr = pIDBInitialize->Initialize();
CHKHR_GOTO(hr, _ExitConnect, "Failed to Connect to the Server.");
//Create a new activity from the data source object.
hr = pIDBInitialize->QueryInterface(IID_IDBCreateSession, (void**) &pIDBCreateSession);
CHKHR_GOTO(hr, _ExitConnect, "Failed to obtain IDBCreateSession interface.");
hr = pIDBCreateSession->CreateSession(NULL, IID_IDBCreateCommand, (IUnknown**) &pIDBCreateCommand);
CHKHR_GOTO(hr, _ExitConnect, "Failed to create a new Session.");
hr = pIDBCreateCommand->CreateCommand(NULL, IID_ICommandText, (IUnknown**) &pICommandText);
CHKHR_GOTO(hr, _ExitConnect, "Failed to create a new Command.");
*ppICommandText = pICommandText;
_ExitConnect:
RELEASE_ITF(pIDBCreateCommand);
for(ULONG uIndexProp = 0; uIndexProp < nInitProps; uIndexProp++)
VariantClear(&InitProperties[uIndexProp].vValue);
RELEASE_ITF(pIDBProperties);
return hr;
}
HRESULT DisConnect() {
HRESULT hr = S_OK;
if (pIDBInitialize)
hr = pIDBInitialize->Uninitialize();
RELEASE_ITF(pIDBInitialize);
return hr;
}
int main() {
HRESULT hr;
const WCHAR* g_wchCmdString = L"{? = call Scenario1 ( ?, ?, ?, ?)};{? = call Scenario1 ( ?, ?, ?, ?)}";
ICommandText* pICommandText = NULL;
IAccessor* pIAccessor = NULL;
HACCESSOR hAccessor = NULL;
IRowset* pIRowset = NULL;
IMultipleResults* pIMultipleResults = NULL;
ISequentialStream* pIStream = NULL;
const ULONG nParams = 10;
ULONG uIndex = 0;
DBBINDING acDBBinding [nParams];
DBBINDSTATUS acDBBindStatus[nParams];
typedef struct tagSPROCPARAMS {
long lReturnValue;
long lInt;
IUnknown* streamVarcharMax;
IUnknown* streamXML;
char chVarChar[21];
long lReturnValue2;
long lInt2;
IUnknown* streamVarcharMax2;
IUnknown* streamXML2;
char chVarChar2[21];
} SPROCPARAMS;
SPROCPARAMS sprocparams[] = {{ 6, 17, NULL, NULL, "", 4, 20, NULL, NULL, ""},{ 5, 23, NULL, NULL, "", 7, 11, NULL, NULL, ""}};
const int nBlobBindingIndexes = 8;
IUnknown** ppBoundBlobs[nBlobBindingIndexes];
int idxBlobBindingCurrent = 0;
ppBoundBlobs[0] = &(sprocparams[0].streamVarcharMax);
ppBoundBlobs[1] = &(sprocparams[0].streamXML);
ppBoundBlobs[2] = &(sprocparams[0].streamVarcharMax2);
ppBoundBlobs[3] = &(sprocparams[0].streamXML2);
ppBoundBlobs[4] = &(sprocparams[1].streamVarcharMax);
ppBoundBlobs[5] = &(sprocparams[1].streamXML);
ppBoundBlobs[6] = &(sprocparams[1].streamVarcharMax2);
ppBoundBlobs[7] = &(sprocparams[1].streamXML2);
LONG cNumRows;
DBPARAMS Params;
hr = Connect(&pICommandText);
if (FAILED(hr))
goto _Exit;
hr = pICommandText->SetCommandText(DBGUID_DBSQL, g_wchCmdString);
CHKHR_GOTO(hr, _Exit, "Failed to Set Command Text.");
hr = pICommandText->QueryInterface(IID_IAccessor, (void**)&pIAccessor);
CHKHR_GOTO(hr, _Exit, "Failed to get IAccessor interface on Command object.");
INIT_BINDINGS(acDBBinding, nParams);
acDBBinding[0].obValue = offsetof(SPROCPARAMS, lReturnValue);
acDBBinding[0].eParamIO = DBPARAMIO_OUTPUT;
acDBBinding[0].cbMaxLen = sizeof(sprocparams[0].lReturnValue);
acDBBinding[0].wType = DBTYPE_I4;
acDBBinding[0].bPrecision = 11;
acDBBinding[1].obValue = offsetof(SPROCPARAMS, lInt);
acDBBinding[1].eParamIO = DBPARAMIO_INPUT | DBPARAMIO_OUTPUT;
acDBBinding[1].cbMaxLen = sizeof(sprocparams[0].lInt);
acDBBinding[1].wType = DBTYPE_I4;
acDBBinding[1].bPrecision = 11;
acDBBinding[2].obValue = offsetof(SPROCPARAMS, streamVarcharMax);
acDBBinding[2].eParamIO = DBPARAMIO_OUTPUT;
acDBBinding[2].cbMaxLen = sizeof(sprocparams[0].streamVarcharMax);
acDBBinding[2].wType = DBTYPE_IUNKNOWN;
acDBBinding[2].pObject = new DBOBJECT;
acDBBinding[2].pObject->dwFlags = STGM_READ;
acDBBinding[2].pObject->iid = IID_ISequentialStream;
acDBBinding[2].bPrecision = 255;
acDBBinding[3].obValue = offsetof(SPROCPARAMS, streamXML);
acDBBinding[3].eParamIO = DBPARAMIO_OUTPUT;
acDBBinding[3].cbMaxLen = sizeof(sprocparams[0].streamXML);
acDBBinding[3].wType = DBTYPE_IUNKNOWN;
acDBBinding[3].pObject = new DBOBJECT;
acDBBinding[3].pObject->dwFlags = STGM_READ;
acDBBinding[3].pObject->iid = IID_ISequentialStream;
acDBBinding[3].bPrecision = 255;
acDBBinding[4].obValue = offsetof(SPROCPARAMS, chVarChar);
acDBBinding[4].eParamIO = DBPARAMIO_OUTPUT;
acDBBinding[4].cbMaxLen = sizeof(sprocparams[0].chVarChar);
acDBBinding[4].wType = DBTYPE_STR;
acDBBinding[4].bPrecision = 255;
acDBBinding[5].obValue = offsetof(SPROCPARAMS, lReturnValue2);
acDBBinding[5].eParamIO = DBPARAMIO_OUTPUT;
acDBBinding[5].cbMaxLen = sizeof(sprocparams[0].lReturnValue2);
acDBBinding[5].wType = DBTYPE_I4;
acDBBinding[5].bPrecision = 11;
acDBBinding[6].obValue = offsetof(SPROCPARAMS, lInt2);
acDBBinding[6].eParamIO = DBPARAMIO_INPUT | DBPARAMIO_OUTPUT;
acDBBinding[6].cbMaxLen = sizeof(sprocparams[0].lInt2);
acDBBinding[6].wType = DBTYPE_I4;
acDBBinding[6].bPrecision = 11;
acDBBinding[7].obValue = offsetof(SPROCPARAMS, streamVarcharMax2);
acDBBinding[7].eParamIO = DBPARAMIO_OUTPUT;
acDBBinding[7].cbMaxLen = sizeof(sprocparams[0].streamVarcharMax2);
acDBBinding[7].wType = DBTYPE_IUNKNOWN;
acDBBinding[7].pObject = new DBOBJECT;
acDBBinding[7].pObject->dwFlags = STGM_READ;
acDBBinding[7].pObject->iid = IID_ISequentialStream;
acDBBinding[7].bPrecision = 255;
acDBBinding[8].obValue = offsetof(SPROCPARAMS, streamXML2);
acDBBinding[8].eParamIO = DBPARAMIO_OUTPUT;
acDBBinding[8].cbMaxLen = sizeof(sprocparams[0].streamXML2);
acDBBinding[8].wType = DBTYPE_IUNKNOWN;
acDBBinding[8].pObject = new DBOBJECT;
acDBBinding[8].pObject->dwFlags = STGM_READ;
acDBBinding[8].pObject->iid = IID_ISequentialStream;
acDBBinding[8].bPrecision = 255;
acDBBinding[9].obValue = offsetof(SPROCPARAMS, chVarChar2);
acDBBinding[9].eParamIO = DBPARAMIO_OUTPUT;
acDBBinding[9].cbMaxLen = sizeof(sprocparams[0].chVarChar2);
acDBBinding[9].wType = DBTYPE_STR;
acDBBinding[9].bPrecision = 255;
hr = pIAccessor->CreateAccessor(
DBACCESSOR_PARAMETERDATA,
nParams,
acDBBinding,
sizeof(SPROCPARAMS),
&hAccessor,
acDBBindStatus);
CHKHR_GOTO(hr, _Exit, "Failed to Create Accessor for the defined parameters.");
Params.pData = &sprocparams;
Params.cParamSets = sizeof(sprocparams)/sizeof(SPROCPARAMS);
Params.hAccessor = hAccessor;
hr = pICommandText->Execute(NULL, IID_IMultipleResults, &Params, &cNumRows, (IUnknown**)&pIMultipleResults);
CHKHR_GOTO(hr, _Exit, "Failed to Execute Command.");
cout << "Command executed successfully, retrieving results." << endl;
idxBlobBindingCurrent = 0;
if (pIMultipleResults) {
for (;;) {
hr = pIMultipleResults->GetResult(NULL, 0, IID_IRowset, NULL, (IUnknown**)&pIRowset);
if (hr == DB_S_NORESULT) {
cout << "All results processed." << endl;
break;
}
if (FAILED(hr)) {
// In this case, user has open rowset or open blobs
if (hr == DB_E_OBJECTOPEN) {
IUnknown* pIUnkCurrent = *ppBoundBlobs[idxBlobBindingCurrent];
if (pIUnkCurrent) {
hr = pIUnkCurrent->QueryInterface(IID_ISequentialStream, (void**)&pIStream);
if (FAILED(hr)) {
cout << "Failed to get a stream object. " << endl;
goto _Exit;
}
RELEASE_ITF(pIUnkCurrent);
// Display the data
char chBuff [51];
wchar_t wchBuff[51];
ULONG cbRead = 0;
do {
if (idxBlobBindingCurrent % 2) {
hr = pIStream->Read(wchBuff, 50 * sizeof(wchar_t), &cbRead);
if (hr == E_UNEXPECTED)
break;
wchBuff[cbRead / 2] = 0;
printf_s("%S", wchBuff[0] == 0xFEFF ? wchBuff+1 : wchBuff);
if (hr == S_FALSE || cbRead < 50 * sizeof(wchar_t)) {
cout << endl;
RELEASE_ITF(pIStream);
break;
}
}
else {
hr = pIStream->Read(chBuff, 50, &cbRead);
if (hr == E_UNEXPECTED)
break;
chBuff[cbRead] = 0;
printf_s("%s", chBuff);
if (hr == S_FALSE || cbRead < 50) {
cout << endl;
RELEASE_ITF(pIStream);
break;
}
}
} while (SUCCEEDED(hr));
if (FAILED(hr) && hr != E_UNEXPECTED) {
cout << "Stream data read failed." << endl;
goto _Exit;
}
idxBlobBindingCurrent++;
continue;
}
}
else {
cout << "GetResult failed with unknown error." << endl;
break;
}
}
else {
if (pIRowset) {
DBCOUNTITEM cRowsObtained;
DBCOUNTITEM cRowsTotal = 0;
HROW hRow[1];
HROW* phRow = hRow;
do {
hr = pIRowset->GetNextRows(0, 0, 1, &cRowsObtained, &phRow);
cRowsTotal += cRowsObtained;
pIRowset->ReleaseRows(cRowsObtained, hRow, NULL, NULL, NULL);
} while (SUCCEEDED(hr) && hr != DB_S_ENDOFROWSET);
cout << "Total number of Rows: " << cRowsTotal << endl;
}
RELEASE_ITF(pIRowset);
}
}
}
// Now display the rest of parameters
printf_s(" lReturnValue : %d\n", sprocparams[0].lReturnValue);
printf_s(" lInt : %d\n", sprocparams[0].lInt);
printf_s(" chVarChar : %s\n", sprocparams[0].chVarChar);
printf_s(" lReturnValue : %d\n", sprocparams[0].lReturnValue2);
printf_s(" lInt : %d\n", sprocparams[0].lInt2);
printf_s(" chVarChar : %s\n", sprocparams[0].chVarChar);
printf_s(" lReturnValue : %d\n", sprocparams[1].lReturnValue);
printf_s(" lInt : %d\n", sprocparams[1].lInt);
printf_s(" chVarChar : %s\n", sprocparams[1].chVarChar);
printf_s(" lReturnValue : %d\n", sprocparams[1].lReturnValue2);
printf_s(" lInt : %d\n", sprocparams[1].lInt2);
printf_s(" chVarChar : %s\n", sprocparams[1].chVarChar);
_Exit:
RELEASE_ITF(pIStream);
RELEASE_ITF(pIRowset);
RELEASE_ITF(pIMultipleResults);
if (pIAccessor) {
pIAccessor->ReleaseAccessor(hAccessor, NULL);
RELEASE_ITF(pIAccessor);
}
RELEASE_ITF(pICommandText);
DisConnect();
}