MDAC 2.5 SDK - ADO

CacheSize Property Example (VC++)

See Also

This example uses the CacheSize property to show the difference in performance for an operation performed with and without a 30-record cache.

#import "C:\Program Files\Common Files\System\ADO\msado15.dll" \
    no_namespace rename("EOF", "EndOfFile")

#include <ole2.h>
#include <stdio.h>
#include <conio.h>
#include <winbase.h>

// Function declarations
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void CacheSizeX();
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);

///////////////////////////////////////////////////////////
//                                                       //
//      Main Function                                    //
//                                                       //
///////////////////////////////////////////////////////////

void main()
{
    if(FAILED(::CoInitialize(NULL)))
        return;

    CacheSizeX();

    ::CoUninitialize();
}

///////////////////////////////////////////////////////////
//                                                       //
//      CacheSizeX Function                              //
//                                                       //
///////////////////////////////////////////////////////////

void CacheSizeX()
{
    // Define ADO object pointers.
    // Initialize pointers on define.
    // These are in the ADODB::  namespace
     _RecordsetPtr    pRstRoySched  = NULL;

     //Define Other Variables
    HRESULT  hr = S_OK;
    DWORD sngStart;
    DWORD sngEnd; 
    float sngNoCache;
    float sngCache;
    int intLoop = 0;
    _bstr_t strTemp;

    _bstr_t strCnn("Provider=sqloledb;Data Source=srv;"
    "Initial Catalog=Pubs;User Id=sa;Password=;");

    try
    {
        //Open the RoySched table.
        TESTHR(pRstRoySched.CreateInstance(__uuidof(Recordset)));
        pRstRoySched->Open("roysched", strCnn, adOpenForwardOnly,
            adLockReadOnly, adCmdTable);

        // Enumerate the Recordset object twice and record
        // the elapsed time.
        sngStart = GetTickCount();

        for (intLoop = 1; intLoop < 2; intLoop++)
        {
            pRstRoySched->MoveFirst();
        
            while(!(pRstRoySched->EndOfFile))
            {
                    // Execute a simple operation for the
                    // performance test.
                    strTemp = pRstRoySched->Fields->
                        Item["title_id"]->Value;
                    pRstRoySched->MoveNext();
            }
        }
        sngEnd = GetTickCount();
        sngNoCache = (float)(sngEnd - sngStart)/(float)1000;

        // Cache records in groups of 30 records.
        pRstRoySched->MoveFirst();
        pRstRoySched->CacheSize = 30;

        sngStart =  GetTickCount();

        // Enumerate the Recordset object twice and record
        // the elapsed time.
        for (intLoop = 1;intLoop < 2; intLoop++)
        {
            pRstRoySched->MoveFirst();
            while(!(pRstRoySched->EndOfFile))
            {
                    // Execute a simple operation for the
                    // performance test.
                    strTemp = pRstRoySched->Fields->
                        Item["title_id"]->Value;
                    pRstRoySched->MoveNext();
            }
        }
        sngEnd =  GetTickCount();
        sngCache = (float)(sngEnd - sngStart)/(float)1000;

        // Display performance results.
        printf("Caching Performance Results:\n");
        printf("No cache: %6.3f  seconds \n", sngNoCache);
        printf("30-record cache: %6.3f  seconds \n", sngCache);

        // Clean up objects before exit.
        pRstRoySched->Close();
    }
    catch(_com_error &e)
    {
         // Notify the user of errors if any.
        _variant_t vtConnect = pRstRoySched->GetActiveConnection();

        // GetActiveConnection returns connect string if connection
        // is not open, else returns Connection object.
        switch(vtConnect.vt)
        {
            case VT_BSTR:
                PrintComError(e);
                break;
            case VT_DISPATCH:
               // Pass a connection pointer accessed from the Recordset.
               PrintProviderError(vtConnect);
               break;
            default:
                printf("Errors occured.");
                break;
        }
    }
}

///////////////////////////////////////////////////////////
//                                                       //
//      PrintProviderError Function                      //
//                                                       //
///////////////////////////////////////////////////////////

void PrintProviderError(_ConnectionPtr pConnection)
{
    // Print Provider Errors from Connection object.

    // pErr is a record object in the Connection's Error collection.
    ErrorPtr pErr  = NULL;

    if( (pConnection->Errors->Count) > 0)
    {
        long nCount = pConnection->Errors->Count;
        // Collection ranges from 0 to nCount -1.
        for(long i = 0; i < nCount; i++)    
        {
            pErr = pConnection->Errors->GetItem(i);
            printf("Error number: %x\t%s", pErr->Number, 
                pErr->Description);
        }
    }
}

///////////////////////////////////////////////////////////
//                                                       //
//      PrintComError Function                           //
//                                                       //
///////////////////////////////////////////////////////////

void PrintComError(_com_error &e)
{
    _bstr_t bstrSource(e.Source());
    _bstr_t bstrDescription(e.Description());
    
    // Print Com errors.  
    printf("Error\n");
    printf("\tCode = %08lx\n", e.Error());
    printf("\tCode meaning = %s\n", e.ErrorMessage());
    printf("\tSource = %s\n", (LPCSTR) bstrSource);
    printf("\tDescription = %s\n", (LPCSTR) bstrDescription);
   
}