Optimize, propriété – Exemple (VC++)

S’applique à : Access 2013, Office 2013

Cet exemple illustre la propriété dynamique Optimize des objets Field. Le champ zip de la table Authors de la base de données Pubs n’est pas indexé. La définition de la propriété Optimize sur True dans le champ zip autorise ADO à créer un index qui améliore les performances de la méthode Find .

 
// BeginOptimizeCpp 
#import "c:\Program Files\Common Files\System\ADO\msado15.dll" no_namespace rename("EOF", "EndOfFile") 
 
#include <ole2.h> 
#include <stdio.h> 
#include <conio.h> 
 
// Function declarations 
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);}; 
void OptimizeX(void); 
void PrintProviderError(_ConnectionPtr pConnection); 
void PrintComError(_com_error &e); 
 
////////////////////////////////////////////////////////// 
// // 
// Main Function // 
// // 
////////////////////////////////////////////////////////// 
void main() 
{ 
 if(FAILED(::CoInitialize(NULL))) 
 return; 
 
 OptimizeX(); 
 
 ::CoUninitialize(); 
} 
 
////////////////////////////////////////////////////////// 
// // 
// OptimizeX Function // 
// // 
////////////////////////////////////////////////////////// 
void OptimizeX(void) 
{ 
 HRESULT hr = S_OK; 
 
 // Define string variables. 
 _bstr_t strCnn("Provider='sqloledb';Data Source='MySqlServer';" 
 "Initial Catalog='pubs';Integrated Security='SSPI';"); 
 // Define ADO object pointers. 
 // Initialize pointers on define. 
 // These are in the ADODB:: namespace. 
 _RecordsetPtr pRst = NULL; 
 
 try 
 { 
 TESTHR(pRst.CreateInstance(__uuidof(Recordset))); 
 
 // Enable Index creation. 
 pRst->CursorLocation = adUseClient; 
 pRst->Open ("SELECT * FROM authors", strCnn, 
 adOpenStatic, adLockReadOnly, adCmdText); 
 
 // Create the index 
 pRst->Fields->GetItem("zip")->Properties-> 
 GetItem("Optimize")->PutValue("True"); 
 
 // Find Akiko Yokomoto 
 pRst->Find("zip = '94595'",1,adSearchForward); 
 printf("\n%s %s %s %s %s\n", 
 (LPSTR) (_bstr_t) pRst->Fields->GetItem("au_fname")->Value, 
 (LPSTR) (_bstr_t) pRst->Fields->GetItem("au_lname")->Value, 
 (LPSTR) (_bstr_t) pRst->Fields->GetItem("address")->Value, 
 (LPSTR) (_bstr_t) pRst->Fields->GetItem("city")->Value, 
 (LPSTR) (_bstr_t) pRst->Fields->GetItem("state")->Value); 
 
 // Delete the index 
 pRst->Fields->GetItem("zip")->Properties-> 
 GetItem("Optimize")->PutValue("False"); 
 } 
 catch (_com_error &e) 
 { 
 // Notify the user of errors if any. 
 // Pass a connection pointer accessed from the Recordset. 
 _variant_t vtConnect = pRst->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: 
 PrintProviderError(vtConnect); 
 break; 
 default: 
 printf("Errors occured."); 
 break; 
 } 
 } 
 
 // Clean up objects before exit. 
 if (pRst) 
 if (pRst->State == adStateOpen) 
 pRst->Close(); 
} 
 
/////////////////////////////////////////////////////////// 
// // 
// 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("\t 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); 
} 
// EndOptimizeCpp