Optimize プロパティの例 (VC++)
この例では、Field オブジェクトの動的 Optimize プロパティを示しています。 Pubs データベース内にある Authors テーブルの zip フィールドにはインデックスが作成されていません。 zip フィールドで Optimize プロパティを True に設定すると、ADO が承認され、Find メソッドのパフォーマンスを改善するインデックスが作成されます。
例
// Optimize_Property_Sample.cpp
// compile with: /EHsc
#import "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 PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);
int main() {
if ( FAILED(::CoInitialize(NULL)) )
return -1;
OptimizeX();
::CoUninitialize();
}
void OptimizeX() {
_bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; 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("%s %s %s %s %s",
(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) {
// Display errors, if any. Pass 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 occurred.");
break;
}
}
// Clean up objects before exit.
if (pRst)
if (pRst->State == adStateOpen)
pRst->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("\t 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);
}
Akiko Yokomoto 3 Silver Ct. Walnut Creek CA