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CacheSize Property Example (VC++)

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

// CacheSize_Property_Sample.cpp
// compile with: /EHsc
#import "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);

int main() {
   if ( FAILED(::CoInitialize(NULL)) )
      return -1;

   CacheSizeX();
   ::CoUninitialize();
}

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

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

   _bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");

   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", sngCache);
   }
   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;
      }
   }

   // Clean up objects before exit.
   if (pRstRoySched)
      if (pRstRoySched->State == adStateOpen)
         pRstRoySched->Close();
}

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);
      }
   }
}

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);
}
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