Exemple d’exécution asynchrone (méthode de notification)

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Les exemples de code inclus dans cette rubrique montrent comment utiliser l’exécution asynchrone (méthode de notification).

Cette fonction utilise la notification asynchrone pour ouvrir cinq connexions et exécute une seule requête sur une instruction de chaque connexion.

  
#define NUMBER_OPERATIONS 5  
int AsyncNotificationSample(void)  
{  
    RETCODE     rc;  
  
    SQLHENV     hEnv              = NULL;  
    SQLHDBC     arhDbc[NUMBER_OPERATIONS]         = {NULL};  
    SQLHSTMT    arhStmt[NUMBER_OPERATIONS]        = {NULL};  
  
    HANDLE      arhDBCEvent[NUMBER_OPERATIONS]    = {NULL};  
    RETCODE     arrcDBC[NUMBER_OPERATIONS]        = {0};  
    HANDLE      arhSTMTEvent[NUMBER_OPERATIONS]   = {NULL};  
    RETCODE     arrcSTMT[NUMBER_OPERATIONS]       = {0};  
  
    rc = SQLAllocHandle(SQL_HANDLE_ENV, NULL, &hEnv);  
    if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;  
  
    rc = SQLSetEnvAttr(hEnv,  
        SQL_ATTR_ODBC_VERSION,  
        (SQLPOINTER) SQL_OV_ODBC3_80,  
        SQL_IS_INTEGER);  
    if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;  
  
    // Connection operations begin here  
  
    // Alloc NUMBER_OPERATIONS connection handles  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        rc = SQLAllocHandle(SQL_HANDLE_DBC, hEnv, &arhDbc[i]);  
        if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;  
    }  
  
    // Enable DBC Async on all connection handles  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        rc= SQLSetConnectAttr(arhDbc[i], SQL_ATTR_ASYNC_DBC_FUNCTIONS_ENABLE, (SQLPOINTER)SQL_ASYNC_DBC_ENABLE_ON, SQL_IS_INTEGER);  
        if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;  
    }  
  
    // Application must create event objects  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        arhDBCEvent[i] = CreateEvent(NULL, FALSE, FALSE, NULL); // Auto-reset, initial state is not-signaled  
        if (!arhDBCEvent[i]) goto Cleanup;  
    }  
  
    // Enable notification on all connection handles  
    // Event  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        rc= SQLSetConnectAttr(arhDbc[i], SQL_ATTR_ASYNC_DBC_EVENT, arhDBCEvent[i], SQL_IS_POINTER);  
        if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;  
    }  
  
    // Initiate connect establishing  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        SQLDriverConnect(arhDbc[i], NULL, (SQLTCHAR*)TEXT("Driver={ODBC Driver 11 for SQL Server};SERVER=your_server;DATABASE=your_database;UID=sa;PWD=your_password;"), SQL_NTS, NULL, 0, NULL, SQL_DRIVER_NOPROMPT);  
    }  
  
    // Can do some other staff before calling WaitForMultipleObjects  
    WaitForMultipleObjects(NUMBER_OPERATIONS, arhDBCEvent, TRUE, INFINITE); // Wait All  
  
    // Complete connect API calls  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        SQLCompleteAsync(SQL_HANDLE_DBC, arhDbc[i], & arrcDBC[i]);  
    }  
  
    BOOL fFail = FALSE; // Whether some connection opening fails.  
  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        if ( !SQL_SUCCEEDED(arrcDBC[i]) )   
            fFail = TRUE;  
    }  
  
    // If some SQLDriverConnect() fail, clean up.  
    if (fFail)  
    {  
        for (int i=0; i<NUMBER_OPERATIONS; i++)  
        {  
            if (SQL_SUCCEEDED(arrcDBC[i]) )   
            {  
                SQLDisconnect(arhDbc[i]); // This is also async  
            }  
            else  
            {  
                SetEvent(arhDBCEvent[i]); // Previous SQLDriverConnect() failed. No need to call SQLDisconnect().  
            }  
        }  
        WaitForMultipleObjects(NUMBER_OPERATIONS, arhDBCEvent, TRUE, INFINITE);   
        for (int i=0; i<NUMBER_OPERATIONS; i++)  
        {  
            if (SQL_SUCCEEDED(arrcDBC[i]) )   
            {     
                SQLCompleteAsync(SQL_HANDLE_DBC, arhDbc[i], &arrcDBC[i]);; // To Complete  
            }  
        }  
  
        goto Cleanup;  
    }  
  
    // Statement Operations begin here  
  
    // Alloc statement handle  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        rc = SQLAllocHandle(SQL_HANDLE_STMT, arhDbc[i], &arhStmt[i]);  
        if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;  
    }  
  
    // Enable STMT Async on all statement handles  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        rc = SQLSetStmtAttr(arhStmt[i], SQL_ATTR_ASYNC_ENABLE, (SQLPOINTER)SQL_ASYNC_ENABLE_ON, SQL_IS_INTEGER);  
        if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;  
    }  
  
    // Create event objects  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        arhSTMTEvent[i] = CreateEvent(NULL, FALSE, FALSE, NULL); // Auto-reset, initial state is not-signaled  
        if (!arhSTMTEvent[i]) goto Cleanup;  
    }  
  
    // Enable notification on all statement handles  
    // Event  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        rc= SQLSetStmtAttr(arhStmt[i], SQL_ATTR_ASYNC_STMT_EVENT, arhSTMTEvent[i], SQL_IS_POINTER);  
        if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;  
    }  
  
    // Initiate SQLExecDirect() calls  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        SQLExecDirect(arhStmt[i], (SQLTCHAR*)TEXT("select au_lname, au_fname from authors"), SQL_NTS);  
    }  
  
    // Can do some other staff before calling WaitForMultipleObjects  
    WaitForMultipleObjects(NUMBER_OPERATIONS, arhSTMTEvent, TRUE, INFINITE); // Wait All  
  
    // Now, call SQLCompleteAsync to complete the operation and get return code  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        SQLCompleteAsync(SQL_HANDLE_STMT, arhStmt[i], &arrcSTMT[i]);  
    }  
  
    // Check return values  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        if ( !SQL_SUCCEEDED(arrcSTMT[i]) ) goto Cleanup;  
    }  
  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        //Do some binding jobs here, set SQL_ATTR_ROW_ARRAY_SIZE   
    }  
  
    // Now, initiate fetching  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        SQLFetch(arhStmt[i]);  
    }  
  
    // Can do some other staff before calling WaitForMultipleObjects  
    WaitForMultipleObjects(NUMBER_OPERATIONS, arhSTMTEvent, TRUE, INFINITE);   
  
    // Now, to complete the operations and get return code  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        SQLCompleteAsync(SQL_HANDLE_STMT, arhStmt[i], &arrcSTMT[i]);  
    }  
  
    // Check return code  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        if ( !SQL_SUCCEEDED(arrcSTMT[i]) ) goto Cleanup;  
    }  
  
    // USE fetched data here!!  
  
Cleanup:  
  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        if (arhStmt[NUMBER_OPERATIONS])  
        {  
            SQLFreeHandle(SQL_HANDLE_STMT, arhStmt[i]);  
            arhStmt[i] = NULL;  
        }  
    }  
  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        if (arhSTMTEvent[i])  
        {  
            CloseHandle(arhSTMTEvent[i]);  
            arhSTMTEvent[i] = NULL;  
        }  
    }  
  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        if (arhDbc[i])  
        {  
            SQLFreeHandle(SQL_HANDLE_DBC, arhDbc[i]);  
            arhDbc[i] = NULL;  
        }  
    }  
  
    for (int i=0; i<NUMBER_OPERATIONS; i++)  
    {  
        if (arhDBCEvent[i])  
        {  
            CloseHandle(arhDBCEvent[i]);  
            arhDBCEvent[i] = NULL;  
        }  
    }  
  
    if (hEnv)  
    {  
        SQLFreeHandle(SQL_HANDLE_ENV, hEnv);  
        hEnv = NULL;  
    }  
  
    return 0;  
}

Cette fonction montre un modèle permettant de démarrer plusieurs opérations simultanément et de les attendre quand la notification asynchrone est utilisée :

#define ODBCVER 0x0380  
#define _SQLNCLI_ODBC  
  
// Global variables  
  
const int g_nConnection = 700;  
SQLHENV g_hEnv = NULL;  
SQLHDBC g_hDbcs[g_nConnection];  
HANDLE g_hevents[g_nConnection];  
  
LONG volatile g_JobDoneNumber;  
  
struct  
{  
    char szOutConnectionString[500];  
    SQLSMALLINT iLen;  
} g_connOut[g_nConnection];  
  
void CALLBACK WaitCallBack(PTP_CALLBACK_INSTANCE Inst, PVOID Context, PTP_WAIT Wait, TP_WAIT_RESULT WaitResult)  
{  
    UINT_PTR i = reinterpret_cast<UINT_PTR>(Context);  
    SQLRETURN rc ;  
    SQLCompleteAsync(SQL_HANDLE_DBC, g_hDbcs[(int)i], &rc);  
    printf("Connection %d done: RC: %d, threadid:%u \n", (int)i, rc, GetCurrentThreadId());  
    InterlockedIncrement(&g_JobDoneNumber);  
}  
  
int _tmain(int argc, _TCHAR* argv[])
{
    for(int i = 0; i< g_nConnection; i++)
        g_hevents[i] = CreateEvent(NULL, FALSE, FALSE, NULL);
  
    PTP_WAIT waits[g_nConnection];
    for(int i = 0; i < g_nConnection; i++)
    {  
        waits[i] = CreateThreadpoolWait(&WaitCallBack, reinterpret_cast<PVOID>((UINT_PTR)i), NULL);
        SetThreadpoolWait(waits[i], g_hevents[i], NULL);
    }

    SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE,&g_hEnv);
    SQLSetEnvAttr(g_hEnv,SQL_ATTR_ODBC_VERSION, (SQLPOINTER)SQL_OV_ODBC3_80, SQL_IS_UINTEGER);
    for(int i = 0; i < g_nConnection; i++)
    {  
        SQLAllocHandle( SQL_HANDLE_DBC, g_hEnv , &g_hDbcs[i]);
        SQLSetConnectAttr(
            g_hDbcs[i],  
            SQL_ATTR_ASYNC_DBC_FUNCTIONS_ENABLE,  
            (SQLPOINTER)SQL_ASYNC_ENABLE_ON,  
            SQL_IS_INTEGER);  
        SQLSetConnectAttr(g_hDbcs[i], SQL_ATTR_ASYNC_DBC_EVENT, g_hevents[i], SQL_IS_POINTER);
    }
  
    // make connections  
    g_JobDoneNumber = 0;  
    for(int i = 0; i < g_nConnection; i++)  
    {  
        SQLDriverConnect(g_hDbcs[i],NULL,
            (SQLCHAR*)"DRIVER={ODBC Driver 18 for SQL Server};Server=your_server;Encrypt=yes;database=your_database;uid=usr;pwd=your_password",
            SQL_NTS, (SQLCHAR*)g_connOut[i].szOutConnectionString, 500, &g_connOut[i].iLen, SQL_DRIVER_NOPROMPT);  
    }

    printf("connect wait..\n");
    while(g_JobDoneNumber < g_nConnection)
        SleepEx(50, false);

    // disconnect  
    for(int i = 0; i < g_nConnection; i++)  
      SetThreadpoolWait(waits[i], g_hevents[i], NULL);

    printf("disconnect wait..\n");
    g_JobDoneNumber = 0;
    for(int i = 0; i < g_nConnection; i++)
        SQLDisconnect(g_hDbcs[i]);

    while(g_JobDoneNumber < g_nConnection)  
    SleepEx(50, false);

    for(int i = 0; i < g_nConnection; i++)  
        CloseThreadpoolWait(waits[i]);  

    for(int i = 0; i < g_nConnection; i++)
    {  
        CloseHandle(g_hevents[i]);
        SQLFreeHandle(SQL_HANDLE_DBC, g_hDbcs[i]);
    }
    SQLFreeHandle(SQL_HANDLE_ENV, g_hEnv);
    return 0;
}

Voir aussi

Microsoft ODBC Driver for SQL Server sur Windows