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DBGridTableView: howto fetch more rows?

6 years 7 months ago #1 by Mathias
hi,
I'm connection a DBGridTableView to a SQLITE database. The problem is, that it only displays the first 256 rows of the database table. How can I force the DBGridTableView to fetch more rows when the end of the view is reached (like the QTableView does).

thanks,
Mathias

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6 years 7 months ago #2 by Piotr
Hi Mathias

SQLite database does not support reporting information about query sizes.

Create your own model class that inherits from QSqlTableModel and declare virtual bool select() function.

class MySQLiteSqlTableModel : public QSqlTableModel
{
Q_OBJECT

public:
MySQLiteSqlTableModel(QObject* parent = 0);

virtual bool select();
};

Create select() function as follows:
#include <QSqlDriver>
...
bool MySQLiteSqlTableModel::select()
{
bool result = QSqlTableModel::select();
if(result && !database().driver()->hasFeature(QSqlDriver::QuerySize))
while(canFetchMore())
fetchMore();

return result;
}

Regards,
Piotr

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6 years 7 months ago #3 by Mathias
Hi Piotr,

thanks for your answer. From my point of view this is not an option, since using your workaround means that the whole database is loaded into memory, which is impossible with my 50GB database. ;)

How is it solved in the orginal QT tableview? Using this widget, the view automatically fetches more rows when the end of the table is reached by scrolling down (and I guess some records at the top of the table are thrown aways).

Kind regards,
Mathias

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6 years 7 months ago #4 by Developer Machines
Support for fetch mode is not implemented at the moment by the following reason. In our opinion, the interface QSqlTableModel/QAbstractItemModel is not enough for the support of sequential mode for tables with large amounts of data. So QTableView use the RowCount() method after the fetchMore() has invoked. We think it is necessary to have Next, Prev, First, Next functions to support large tables (sequential mode). In this case the grid's scroller should have 3 pos only (First, Last, Current). According to my information QTablleVIew does not support this mode.

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