CBulkRowset Class
Fetches and manipulates rows to work on data in bulk by retrieving multiple row handles with a single call.
Syntax
template <class TAccessor>
class CBulkRowset : public CRowset<TAccessor>
Parameters
TAccessor
An accessor class.
Requirements
Header: atldbcli.h
Members
Methods
| Name | Description |
|---|---|
| AddRefRows | Increments the reference count. |
| CBulkRowset | Constructor. |
| MoveFirst | Retrieves the first row of data, performing a new bulk fetch if necessary. |
| MoveLast | Moves to the last row. |
| MoveNext | Retrieves the next row of data. |
| MovePrev | Moves to the previous row. |
| MoveToBookmark | Fetches the row marked by a bookmark or the row at a specified offset from that bookmark. |
| MoveToRatio | Fetches rows starting from a fractional position in the rowset. |
| ReleaseRows | Sets the current row (m_nCurrentRow) to zero and releases all rows. |
| SetRows | Sets the number of row handles to be retrieved by one call. |
Example
The following example demonstrates use of the CBulkRowset class.
class CCustomerData
{
public:
char m_szField1[50];
BEGIN_COLUMN_MAP(CCustomerData)
COLUMN_ENTRY(1, m_szField1)
END_COLUMN_MAP()
};
void DoCBulkRowsetTest()
{
CoInitialize(NULL);
CCommand<CAccessor<CCustomerData>, CBulkRowset > cmd;
CDataSource ds;
// Open up data link dialogs to create a data source
ds.Open();
CSession session;
session.Open(ds);
// Could call SetRows() here if you want to fetch
// more than 10 HROWs at a time.
cmd.Open(session, L"Select * from customer");
cmd.MoveFirst();
// Note that the CBulkRowset by default fetched 10 HROWs at a time
// so that the MoveNext call will not have to make the GetNextRows
// call to get the second HROW because it has already been fetched
//by the MoveFirst() call above.
cmd.MoveNext();
cmd.Close();
session.Close();
ds.Close();
}
CBulkRowset::AddRefRows
Calls IRowset::AddRefRows to increment the reference count for all rows currently retrieved from the bulk rowset.
Syntax
HRESULT AddRefRows() throw();
Return Value
A standard HRESULT.
CBulkRowset::CBulkRowset
Creates a new CBulkRowset object and sets the default row count to 10.
Syntax
CBulkRowset();
CBulkRowset::MoveFirst
Retrieves the first row of data.
Syntax
HRESULT MoveFirst() throw();
Return Value
A standard HRESULT.
CBulkRowset::MoveLast
Moves to the last row.
Syntax
HRESULT MoveLast() throw();
Return Value
A standard HRESULT.
CBulkRowset::MoveNext
Retrieves the next row of data.
Syntax
HRESULT MoveNext() throw();
Return Value
A standard HRESULT. When the end of the rowset has been reached, returns DB_S_ENDOFROWSET.
CBulkRowset::MovePrev
Moves to the previous row.
Syntax
HRESULT MovePrev() throw();
Return Value
A standard HRESULT.
CBulkRowset::MoveToBookmark
Fetches the row marked by a bookmark or the row at a specified offset (lSkip) from that bookmark.
Syntax
HRESULT MoveToBookmark(const CBookmarkBase& bookmark,
DBCOUNTITEM lSkip = 0) throw();
Parameters
bookmark
[in] A bookmark marking the location from which you want to fetch data.
lSkip
[in] The number count of rows from the bookmark to the target row. If lSkip is zero, the first row fetched is the bookmarked row. If lSkip is 1, the first row fetched is the row after the bookmarked row. If lSkip is -1, the first row fetched is the row before the bookmarked row.
Return Value
See IRowset::GetData in the OLE DB Programmer's Reference.
CBulkRowset::MoveToRatio
Fetches rows starting from a fractional position in the rowset.
Syntax
HRESULT MoveToRatio(DBCOUNTITEM nNumerator,
DBCOUNTITEM nDenominator)throw();
Parameters
nNumerator
[in] The numerator used to determine the fractional position from which to fetch data.
nDenominator
[in] The denominator used to determine the fractional position from which to fetch data.
Return Value
A standard HRESULT.
Remarks
MoveToRatio fetches the rows roughly according to the following formula:
(nNumerator * RowsetSize ) / nDenominator
Where RowsetSize is the size of the rowset, measured in rows. The accuracy of this formula depends on the specific provider. For details, see IRowsetScroll::GetRowsAtRatio in the OLE DB Programmer's Reference.
CBulkRowset::ReleaseRows
Calls IRowset::ReleaseRows to decrement the reference count for all rows currently retrieved from the bulk rowset.
Syntax
HRESULT ReleaseRows() throw();
Return Value
A standard HRESULT.
CBulkRowset::SetRows
Sets the number of row handles retrieved by each call.
Syntax
void SetRows(DBROWCOUNT nRows) throw();
Parameters
nRows
[in] The new size of the rowset (number of rows).
Remarks
If you call this function, it must be before the rowset is opened.
See also
OLE DB Consumer Templates
OLE DB Consumer Templates Reference