HOWTO: Compacting Microsoft Access Database Through OLE DB
http://support.microsoft.com/default.aspx?scid=kb;EN-US;230496
SUMMARY
OLE DB specification doesn't provide interfaces to compact or repair databases. However, the OLE DB Provider for Microsoft Jet version 4.0 exposes this functionality through a custom interface: IJetCompact (TDataSource cotype). IJetCompact is defined in the header file Jetoledb.h that can be obtained separately from Microsoft (Please see knowledge base article Q228525).
MORE INFORMATION
To repair and compact a Microsoft Access database using OLE DB, MDAC 2.1 or higher version must be properly installed on the computer. The following steps are required:
1. Create and initialize the data source objects by using interfaces of IDBInitialize and IDBCreateSession.
2. Use GetJetEngineType function to get the version of Jet database.
3. Fill a DBPROPSET structure with information about the destination database to compact to.
4. Query the IDBCreateSession object for the Jet Compact object: IJetCompact.
5. Call IJetCompact's Compact method passing in the DBPROPSET created in step 2.
The following code demonstrates the earlier steps using Visual C++ ATL OLE DB consumer templates:
#include <objbase.h>
#define DBINITCONSTANTS
#define INITGUID
#include <initguid.h>
#include <oledb.h>
#include "msjetoledb.h"
#include "jetoledb.h" // for IJetCompact interface
#include <atldbcli.h>
long GetJetEngineType( LPCTSTR src );
class OLEINITIALIZE
{
bool m_bOleInit;
public:
OLEINITIALIZE()
{
m_bOleInit= (CoInitialize(NULL)==S_OK);
}
~OLEINITIALIZE()
{
if (m_bOleInit)
CoUninitialize();
}
};
HRESULT CompactDatabase(LPCTSTR src, LPCTSTR dest)
{
// Initialize environment must be the first line in your function
OLEINITIALIZE oleinit;
CDataSource ds;
CComPtr<IJetCompact> spJetCompact =NULL;
CComPtr<IDBCreateSession> spSession =NULL;
HRESULT hr=0;
//Specify the source DSO
ds.Open(CLSID_JETOLEDB_4_00, src);
CDBPropSet propset1(DBPROPSET_DBINIT);
propset1.AddProperty(DBPROP_INIT_DATASOURCE, dest);
long x = GetJetEngineType( src );
CDBPropSet propset2(DBPROPSET_JETOLEDB_DBINIT);
propset2.AddProperty(DBPROP_JETOLEDB_ENGINE, x);
CDBPropSet dbsets[2] = { propset1, propset2 };
// Have we connected to the database?
ATLASSERT(ds.m_spInit != NULL);
hr = ds.m_spInit->QueryInterface(IID_IDBCreateSession, (void**)&spSession);
if (FAILED(hr))
return hr;
//IJetCompact only supported in Jet 4.0 and above
hr = spSession->QueryInterface( __uuidof(IJetCompact), (void**)&spJetCompact);
if (FAILED(hr))
return hr;
//Delete the destination file if it exists
remove(dest);
//Ok compact
//hr = spJetCompact->Compact(1, &propset);
hr = spJetCompact->Compact(1, dbsets);
if (FAILED(hr))
return hr;
return hr;
}
long GetJetEngineType( LPCTSTR src )
{
HRESULT hr;
CDataSource ds;
CComBSTR bstrSource;
VARIANT vPropValue;
// Initialize our variant to VT_I4 and 0.
vPropValue.vt = VT_I4;
vPropValue.lVal = 0L;
// Exit now if source database is null.
if( NULL == src ) return 0;
// Build connection string for source.
bstrSource = L"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=";
bstrSource += src;
bstrSource += L";";
hr = ds.OpenFromInitializationString( bstrSource );
hr = ds.GetProperty( DBPROPSET_JETOLEDB_DBINIT, DBPROP_JETOLEDB_ENGINE, &vPropValue );<BR/>
<BR/>
// Version returned will be one of these values:
//
// #define JETDBENGINETYPE_UNKNOWN 0x00
// #define JETDBENGINETYPE_JET10 0x01
// #define JETDBENGINETYPE_JET11 0x02
// #define JETDBENGINETYPE_JET2X 0x03
// #define JETDBENGINETYPE_JET3X 0x04
// #define JETDBENGINETYPE_JET4X 0x05
return vPropValue.lVal;
}
NOTE:
1. If you have a compiler error such as:
DBPROP_JETOLEDB_ENGINE undefined specifier
For additional information about updated Jet header files, please click the article number below to view the article in the Microsoft Knowledge Base:
228525 PATCH: JetVC.exe VC++ Support Files for the Jet OLE DB Provider
2. Inline the GetJetEngineType function in your code if you don't want to open another connection.
3. Compacting a database also repairs the database, unlike in DAO where it was a separate functionality. In OLE DB there is no way to only repair a database.
REFERENCES
For additional information, please click the article number below to view the article in the Microsoft Knowledge Base:
230501 HOWTO: Compacting Microsoft Access Database via ADO
The information in this article applies to:
